Organometallic Chemistry Is Described to Better Acquaint the Reader with the Field
A Dissertation
Entitled
Synthesis, Reactivity, and Catalysis of 3-Iminophosphine Palladium Complexes
by
Andrew Ronald Shaffer
Submitted as partial fulfillment of the requirements for
the Doctor of Philosophy in Chemistry
______Advisor: Joseph A. R. Schmidt
______Committee Member: Mark R. Mason
______Committee Member: Yun-Ming Lin
______Committee Member: Brian Ashburner
______College of Graduate Studies
The University of Toledo
August 2009
An Abstract of
Synthesis, Reactivity, and Catalysis of 3-Iminophosphine Palladium Complexes
by
Andrew Ronald Shaffer
Submitted as partial fulfillment of the requirements for
The Doctor of Philosophy in Chemistry
The University of Toledo
August 2009
Chapter 1. A brief outline, as well as a time table, of organometallic chemistry is described to better acquaint the reader with the field. Several detailed explanations of catalysis, specifically hydroamination, aryl amination, and Suzuki cross-coupling are presented in a very general context. Finally, basic principles of ligands and their design are outlined, as well as the importance of the research conducted herein.
Chapter 2. Twenty-six new α,β-unsaturated β-chloroimines were synthesized from commercially available ketones using the Vilsmeier-Haack reagent, followed by Schiff- base condensation. Each imine was subsequently converted to an α,β-unsaturated 3- iminophosphine through either late-metal catalyzed phosphorus-carbon cross-coupling or via an addition/elimination sequence. Depending on the substituents present on the vinyl
ii group, the resultant phosphines were isolated as either E- or Z-diastereomers with
successful isolation of predominately single diastereomers for all twenty-seven new
phosphines investigated.
Chapter 3. Several palladium(II) 3-iminophosphine complexes were synthesized in
moderate to high yield. With relevance to many palladium-catalyzed coupling reactions,
these complexes incorporated a wide variety of ligands, including amines, alkyls, allyls,
and triflates. The presence of both η1- and η2-coordination modes demonstrates the hemilability of the 3-iminophosphine ligand class, as determined by X-ray
crystallography and NMR spectroscopy.
Chapter 4. Catalytic screening of various palladium(II) 3-iminophosphine complexes led
to the generation of a wide array of products. The catalytic systems investigated were
hydroamination and several cross-coupling reactions including aryl amination and Suzuki
cross-coupling. The final products of the catalyses were monitored by GC for product
conversion while being isolated and characterized by standard organic techniques and
spectroscopy.
iii
Dedicated to
Patrica and Charles Walker
my grandparents
and
Debra and Joseph Thompson
my parents
and
Melissa Shaffer
my wife
iv Acknowledgements
While you cannot choose who your family is, I was extremely blessed with an outstanding one, and without them, I would not be the person I am today and would not have aspired to ask more of myself. In particular, I would like to thank my mom and my dad for not only unwavering support, but for co-signing quite a few loans to get me through 23 years of school. Together, their advice has been of the highest quality and without their help, I would have quit a long time ago. I am eternally grateful to my gram and pap for always allowing me to have a place to call home. Some of my greatest qualities are a direct result of their teachings and beliefs and I hope that I will be half the inspiration to others as they were to me. I would also like to thank my uncles and their wives for being positive influences on how to live with your soul mate and how to raise incredible children. Finally, I would like to thank my cousins, as well as the rest of my extended family for the laughs, cries, and great stories that I have been fortunate enough to be part of.
You do however get to choose who your friends are. Growing up as a lonely child, I looked to my friends as my brothers and sisters and I would without thinking push an innocent bystander in front of a bullet for them. I think it would be best to start with the first friend I had. Jeff Spagnolla and I were probably the hardest working dishwashers Mahaffey ever saw and will see. Those hours would have seemed unending without his companionship. When I changed schools at the beginning of 7th grade, I was
fortunate enough to meet my best friend Matt as well as JT, Curt, and Cliff. And while the stories we have shared would probably make a great novel, publishing it would probably get us either subpoenaed or arrested. When I attended UPJ with Curt and Matt,
v I had the opportunity to meet several other unique individuals that I am fortunate enough to call friends. At any time, I am sure Aric, Munster, Danimal, Ted, Hartman, Seth,
Janet, Jess, Justin, Tyson, Doug, Joe, Dan, Troy, Kelli, and Ashely could tell you their favorite Bad One story. It was only with their help that I was able to remain sane enough to be a chemistry major. The final group of friends is those that I have made at my time at UT. Without the occasional rant, deathmatch, or pickup game, it would have been impossible to be the indentured servant that I needed to be throughout grad school. A special thanks to my first two lab mates who endured the ‘Dark Times’ with me as well as to Matt for the multiple 7-11 days we shared together. And a final thank you for the remaining three, who by joining the lab allowed the boss to let me move on.
While my family developed my morals and beliefs, there were a few teachers that inspired me. Mrs. Spencer, my 3rd grade teacher and Mr. Love, my 6th grade teacher,
instilled a fire that I rely on even now to motivate me. Their greatest lesson was teaching me never to believe you are worthless and you can succeed no matter what your address is or what side of the bridge you were raised. My love of science started in 10th grade
with Mr. Petrunak’s College Prep Biology class mainly because his relentliness to accept
average always challenged me. Well, I wouldn’t probably have been a chemist, unless it was for Ms. Mellot’s classes because it was there I found myself and realized that chemistry was my calling. While I could list a whole set of professors who have helped me get through undergraduate and graduate school, I will only list two. Dr. Joseph
Carney was the epitamey of what I thought a scientist should be: crazy style, focused,
and scatter brained (but only because he was thinking about twenty things at once). Dr. C
was not only my undergraduate advisor, but a true inspiration. He was the largest reason
vi I thought of becoming an analytical chemist and was always very supportive as well as very understanding. Dr. Joseph Schmidt was about as different from Dr. C as one could get. Joe was hip, young, energetic, and just as brilliant, only more composed. Without his guidance and oversight (he literally looked over my shoulder for the first two years of my graduate life), I would not be half the synthetic chemist I am. His constant encouragement and support inspired me to always demand more out of my skills and for me to learn new ones as well. If certain traits were not driven home as firmly as they were, I would have probably blown myself up, burnt down or flooded the lab, or died from phosphine asphyxiation.
The last person I would like to thank is my wife, Melissa. She was not only a source of inspiration but that of comfort. She allowed me to see life outside of lab and has taught me how to care about life, not work. And although we have had our ups and downs, I would not trade a single down for an up with someone else. Your love and support brings peace to my heart and I will spend the rest of my life thanking you for your love, patience and understanding. I love you.
vii VITA
June 1, 1981 – Born – Clearfield, PA
2004 Bachelor of Science, University of Pittsburgh at Johnstown
2004-2009 Research/Teaching Assistant, The University of Toledo
2009 Doctor of Philosophy, The University of Toledo
Publications
Shaffer, A. R.; Schmidt, J. A. R. Palladium(II) 3-Iminophosphine Complexes as
Intermolecular Hydroamination Catalysts for the Formation of Imines and Enamines.
Organometallics 2008, 27, 1259-1266.
Shaffer, A. R.; Schmidt, J. A. R.. A Versatile Methodology for the Synthesis of α,β-
Unsaturated 3-Iminophosphines. Chemistry-A European Journal 2009, 15, 2662-2673.
Shaffer, A. R.; Schmidt, J. A. R. Reactivity of (3-Iminophosphine)Palladium(II)
Complexes: Evidence of Hemilability. Organometallics 2009, 28, 2494-2504.
viii Table of Contents
Abstract...... ii
Dedication...... iv
Acknowledgements...... v
Vita...... viii
Publications...... viii
Table of Contents...... ix
List of Figures...... xii
List of Schemes...... xiv
List of Tables...... xvi
Chapter I: A Brief Introduction to Organometallic Chemistry, Catalysis, and P-N
Ligands
I-1. Organometallic Chemistry...... 2
I-2. Catalysis...... 5
I-3. Hydroamination...... 7
I-4. Cross-Coupling Reactions
Suzuki-Miyaura Coupling...... 14
Buchwald-Hartwig Coupling (Aryl Amination)...... 16
I-5. Ligands for Metals...... 17
I-6. P-N Ligands...... 19
Chapter II: Synthesis, Isolation, and Characterization of α,β-Unsaturated 3-
Iminophosphines
II-1. Introduction...... 24
ix Table of Contents continued
II-2. Results and Discussion
1st Generation 3-Iminophosphine Ligands...... 26
2nd Generation 3-Iminophosphine Ligands...... 41
II-3. Experimental Methods...... 45
II-4. Conclusion...... 88
Chapter III: Synthesis, Isolation, and Characterization of 3-Iminophosphine
Palladium(II) Complexes
III-1. Introduction...... 91
III-2. Results and Discussion
1st Generation Palladium Complexes...... 92
2nd Generation Palladium Complexes...... 93
III-3. Experimental Methods...... 109
III.4. Conclusion...... 154
Chapter IV: Hydroamination and Cross-Coupling using 3-Iminophosphine
Palladium(II) Complexes
IV-1. Introduction...... 156
IV-2. Results and Discussion
Hydroamination...... 158
Buchwald-Hartwig Coupling (Aryl Amination)...... 163
Suzuki Cross-Coupling...... 174
IV-3. Experimental Methods...... 176
IV-4. Conclusion...... 182
x Table of Contents continued
References...... 184
Appendix 1: Table of Compounds...... 219
Appendix 2: Modified Literature Preparations
A2-1. Bis(1,5-cyclooctadiene)nickel(0): Ni(COD)2…………...... 224
A2-2. Tetrakis(triphenylphosphine)nickel(0): Ni(PPh3)4……...... 224
A2-3. Sodium diphenylphosphide: NaPPh2………………...... …..225
A2-4. Lithium diphenylphosphide: LiPPh2……………………...... 225
A2-5. Diphenyl(trimethylsilyl)phosphine: Ph2PSiMe3……...... 226
A2-6. Aryl boronic acids: ArB(OH)2………………………...... …....226
A2-7. Tris(pentafluorophenyl)borane: B(C6F5)3…………...... 227
A2-8. Lithium tetrakis(pentafluorophenyl)borate: LiB(C6F5)4…...... 227
xi List of Figures
Figure 1. Various P-N ligands...... 21
i Figure 2. ORTEP diagram of PhCCl=CHCH=N(2,6- Pr2C6H3) (2e)...... 29
t i Figure 3. ORTEP diagram of BuCCl=CHCH=N(2,6- Pr2C6H3) (2j)...... 30
Figure 4. ORTEP diagram of PhCCl=CMeCH=NPh (2l)...... 31
Figure 5. ORTEP diagram of tBuCN(H)Ph=CHCH=N(H)+Ph (4)...... 32
Figure 6. ORTEP diagram of 5...... 33
Figure 7. ORTEP diagram of (C3H5)(3b)PdCl (7)...... 37
Figure 8. ORTEP diagram of 3f...... 41
Figure 9. ORTEP diagram of 3p...... 45
Figure 10. ORTEP diagram of PhCCl=CHCH=N(2,6-Me2C6H3) (2c)...... 87
Figure 11. ORTEP diagram of PhCCl=CHCH=N(2,6-Et2C6H3) (2d)...... 87
t Figure 12. ORTEP diagram of BuCCl=CHCH=N(2,6-Me2C6H3) (2h)...... 88
Figure 13. ORTEP diagram of 9a...... 94
Figure 14. ORTEP diagram of 9h...... 94
Figure 15. ORTEP diagram of 9m...... 95
Figure 16. ORTEP diagram of 10a...... 97
Figure 17. ORTEP diagram of 11a...... 98
Figure 18. ORTEP diagram of 11c...... 99
Figure 19. ORTEP diagram of 12a...... 101
Figure 20. ORTEP diagram of 13a...... 103
Figure 21. ORTEP diagram of 14...... 104
Figure 22. ORTEP diagram of 15a...... 106
xii List of Figures continued
Figure 23. ORTEP diagram of 16...... 107
Figure 24. ORTEP diagram of 15b...... 108
Figure 25. ORTEP diagram of 15b’...... 108
Figure 26. ORTEP diagram of 9a’...... 151
Figure 27. ORTEP diagram of 9d...... 151
Figure 28. ORTEP diagram of 9e...... 152
Figure 29. ORTEP diagram of 9f...... 152
Figure 30. ORTEP diagram of 9j...... 153
Figure 31. ORTEP diagram of 9k...... 153
Figure 32. Effect of concentration on the hydroamination of 1,3-cyclohexadiene with
morpholine in the presence of 11a...... 161
Figure 33. Effect of amine pKb on catalyst activity of 11a towards hydroamination....163
Figure 34. Effect of aniline substitution on aryl amination...... 169
Figure 35. Effect of aryl halide substitution on aryl amination...... 173
xiii List of Schemes
Scheme 1. Fischer-Tropsch reaction...... 3
Scheme 2. Hydroformylation of propene...... 4
Scheme 3. Polymerization of ethylene...... 4
Scheme 4. Epoxidation of propene...... 5
Scheme 5. Intramolecular hydroamination catalyzed by a lanthanide or an early
transition metal...... 9
Scheme 6. Late transition metal catalyzed intramolecular hydroamination...... 9
Scheme 7. Early transition metal catalyzed intermolecular hydroamination...... 11
Scheme 8. Late transition metal catalyzed intermolecular hydroamination by a
zwitterionic intermediate...... 12
Scheme 9. Intermolecular hydroamination by late transition metal-amide complex
utilizing oxidative addition and reductive elimination...... 12
Scheme 10. Intermolecular hydroamination of conjugated systems catalyzed by a late
transition metal-hydride...... 13
Scheme 11. General catalytic cycle for Suzuki-Miyaura coupling...... 15
Scheme 12. Alternative mechanism for Suzuki-Miyaura coupling...... 15
Scheme 13. Buchwald-Hartwig coupling (aryl amination) mechanism...... 17
Scheme 14. Synthesis of aliphatic α,β-unsaturated β-chloroimines (2a-o)...... 27
Scheme 15. Attempted isolation of 2g results in addition of aniline to yield 4...... 30
Scheme 16. Oxidative addition of 2d to Pd(0)...... 32
Scheme 17. Substitution of chloride with phosphide results in rapid reductive
elimination...... 34
xiv
List of Schemes continued
Scheme 18. Coordination of 3b to [(allyl)PdCl]2...... 36
Scheme 19. Synthesis of alicyclic α,β-unsaturated β-chloroimines (2p-z)...... 42
Scheme 20. Coordination of 1st generation 3-iminophosphines to palladium(II)
chloride...... 92
Scheme 21. Coordination of 2nd generation 3-iminophosphines to palladium(II)
halide...... 93
Scheme 22. Coordination of 2nd generation 3-iminophosphine to (allyl)palladium(II)
chloride and subsequent salt metathesis...... 96
Scheme 23. Amine coordination...... 100
Scheme 24. Salt metathesis of 9a...... 102
Scheme 25. Alkylation of 9a...... 105
Scheme 26. Synthesis of 15b...... 105
Scheme 27. Hydroamination of 1,3-cyclohexadiene (A) and phenylacetylene (B)...... 158
Scheme 28. General reaction of primary amines with aryl halides...... 163
xv List of Tables
Table 1. Schiff base condensation of aliphatic α,β-unsaturated β-chloroaldehydes (1a-c)
to form α,β-unsaturated β-chloroimines (2a-o)...... 28
Table 2. Metal-catalyzed cross-coupling of aliphatic α,β-unsaturated β-chloroimines
with diphenyl(trimethylsilyl)phosphine...... 35
Table 3. Conversion of aliphatic α,β-unsaturated β-chloroimines (2a-o) to 3-
iminophosphines (3a-o)...... 39
Table 4. Schiff base condensation of alicyclic α,β-unsaturated β-chloroaldehydes to
form alicyclic α,β-unsaturated β-chloroimines (2p-z)...... 43
Table 5. Conversion of alicyclic α,β-unsaturated β-chloroimines (2p-z) to 3-
iminophosphines (3p-aa)...... 44
Table 6. Crystal Data and Collection Parameters...... 81
Table 7. Crystal Data and Collection Parameters...... 82
Table 8. Crystal Data and Collection Parameters...... 83
Table 9. Crystal Data and Collection Parameters...... 84
Table 10. Crystal Data and Collection Parameters...... 85
Table 11. Crystal Data and Collection Parameters...... 86
Table 12. Crystal Data and Collection Parameters...... 141
Table 13. Crystal Data and Collection Parameters...... 142
Table 14. Crystal Data and Collection Parameters...... 143
Table 15. Crystal Data and Collection Parameters...... 144
Table 16. Crystal Data and Collection Parameters...... 145
Table 17. Crystal Data and Collection Parameters...... 146
xvi List of Tables continued
Table 18. Crystal Data and Collection Parameters...... 147
Table 19. Crystal Data and Collection Parameters...... 148
Table 20. Crystal Data and Collection Parameters...... 149
Table 21. Crystal Data and Collection Parameters...... 150
Table 22. Hydroamination of 1,3-cyclohexadiene using 3p, 9a, 10a, 11a...... 159
Table 23. Effect of 1,3-cyclohexadiene to morpholine ratio and solvent effects...... 160
Table 24. Hydroamination of phenylacetylene...... 162
Table 25. Aryl amination of secondary amines with bromobenzene and
bromotoluene...... 165
Table 26. Aryl amination of substituted primary anilines with bromobenzene...... 167
Table 27. Aryl amination of primary amines with bromobenzene...... 168
Table 28. Aryl amination with halobenzonitriles...... 170
Table 29. Aryl amination with para-substituted aryl halides...... 171
Table 30. Aryl amination with di-n-butylamine...... 172
Table 31. Suzuki coupling of boronic acids with aryl halides...... 174
Table 32. Suzuki coupling in the presence of different bases and solvents...... 176
Table 33. Gas Chromatography Collection Parameters...... 181
xvii
Chapter 1:
──────────────────────────────
A Brief Introduction to Organometallic Chemistry, Catalysis,
and P-N Ligands
──────────────────────────────
1 I-1: Organometallic Chemistry
Organometallic chemistry is the chemistry of metal-carbon bonds, and
compounds containing at least one metal-carbon bond are referred to as organometallic
compounds. A major feature of organometallic compounds is the partial positive charge
that resides on the metal, resulting in ligands which have significant carbanionic
character. Carbanions, from organic chemistry, are nucleophilic and for this reason,
organometallic compounds are often employed in carbon-carbon bond forming
reactions.1-4 One class of organometallic compounds contains s- and p-block metals, also
known as main group metals, and includes organolithium and organomagnesium species
such as the Grignard reagent (RMgX), as well as aluminum and gallium complexes.4
These compounds, which tend to be air and moisture sensitive, are often employed as stoichiometric alkyl group transfer reagents; however, there has been some recent success using these metals as catalysts.5-8 Early transition metals are those on the left side of the
transition series and include the lanthanide and actinide series as well. Their complexes
compose the second class of organometallic compounds. These complexes have shown
utility as catalysts in a variety of reactions such as polymerization,4, 9-14 hydroamination,7,
9, 10, 15-43 hydrogenation,44-48 and epoxidation44, 49-56 and generally are air and moisture
sensitive compounds. The final type of organometallic compounds includes those using
late transition metal complexes (metals on the right side of the transition series). Unlike
both of the aforementioned classes, late transition metals are more air and moisture
tolerant and are very commonly employed as catalysts,2-4, 7, 41, 42, 44, 51, 52, 57-67 although their use as stoichiometric transfer reagents is also well documented.1, 3, 4, 52, 67 Beyond their use in organic transformations, organometallic compounds play an important role in
2 metal-mediated biological processes. Several enzymatic transformations have been
linked to the coenzyme vitamin B12, which contains an enzyme-active cobalt metal
center.68
The earliest known organometallic compound is Zeise’s salt.3 Initially, this
compound was thought to be of the formula KCl·PtCl2·EtOH but in the 1950’s it was
determined that this compound undergoes dehydration, forming K[PtCl3(C2H4)]·H2O, with a side-bound ethylene and an outer sphere water.1 One significant advancement in organometallic chemistry in the early 20th century involved the catalytic cracking of
petroleum by first aluminum chloride and acidic clays, which then was followed by the
Houdry Process, which used acid-treated montmorillonite clay or aluminosilicates.
Around the same time, German scientists were able to chemically synthesize simple
alkanes, alkenes, and alcohols by Fischer-Tropsch chemistry (Scheme 1).3 This process
involved passing a mixture of carbon monoxide and hydrogen gas over a heterogeneous
catalyst, linking chains of carbon atoms to form alkanes, as well as terminal alcohols and
alkenes. In 1938, Roelen and coworkers discovered the process of hydroformylation, a
method for the formation of aldehydes from alkenes, carbon monoxide and hydrogen gas
(Scheme 2).3, 4 The mid-20th century saw an explosion of organometallic chemistry. One
of the most important discoveries in this era was polyethylene, especially high density
polyethylene (Scheme 3).3 Subsequently, several other polymerization reactions soon
emerged. Another advancement at this time was olefin metathesis, which includes ring-
cat. CH3(CH2)nCH2OH+ CH3(CH2)nCH=CH2 CO + H2 ++CH3(CH2)nCH3 H2O
Scheme 1. Fischer-Tropsch reaction.
3 CHO Rh or Co cat. CH3CH=CH2 ++CO + H2 CH3CH2CH2CHO CH3CHCH3
Scheme 2. Hydroformylation of propene.
opening/closing and cross metathesis of alkenes.3 Olefin metathesis allowed for the
formation of terminal alkenes from internal alkenes, which was very important because
the majority of alkenes from crude oil are not terminal and the conversion of terminal
alkenes to primary alcohols is much more readily achieved than from internal alkenes.
Also at this time, zeolites were introduced in petroleum refining, providing a higher
gasoline yield and increased product selectivity from catalytic cracking in tandem with a
reduction in coke formation. The early 1960’s saw the development of two very
important classes of reactions.3, 4 The first was a process to create carboxylic acids from
alcohols using carbon monoxide as the carbonyl source. The importance of this reaction
was not only that it used carbon monoxide as a building block but also because it allowed
aldehydes to be utilized in the synthesis of other products, rather than being consumed as
carboxylic acid precursors. The second advancement was the discovery of the first cross-
coupling reactions with Suzuki reagents.2-4 Cross-coupling reactions provide a means to
synthesize new carbon-carbon or carbon-heteroatom bonds without having to handle dangerous reagents such as organolithium or organomagnesium species. One final significant reaction was the discovery of catalytic, stereospecific epoxidation of alkenes in the 1980’s (Scheme 4).51 Even though initially the alkene had to be activated by an
alcohol, stereospecific epoxidation is important because of its ability to create two
adjacent chiral centers in one step. Ti cat. n CH2=CH2 (CH2CH2)n Scheme 3. Polymerization of ethylene.
4 O t Ti cat. BuOOH + CH3CH2=CH2 CH3CHCH2 -tBuOH Scheme 4. Epoxidation of propene.
I-2: Catalysis
A catalyst is any compound which lowers the activation energy of a chemical reaction without being consumed in the process.1-4 One of the most important advantages
of catalyst use is the ability to achieve products at lower reaction temperatures or in less
time. Catalysts also allow for certain processes to proceed by activating a substrate, as is
the case in the addition of amines to alkenes and alkynes. Other advantages include the
ability to control enantio- and diastereoselectivity of products. Catalysts have been
employed in a wide range of reactions including condensations of amines and ketones,
polymerization, petroleum refinement, oxidation/reduction of alkenes, hydrogenation,
and carbonylation and are important to several areas of society, including the oil,
pharmaceutical, textile, automotive, and fine-chemical industries.3, 52, 67
Catalysts are traditionally classified as either heterogeneous or homogeneous
based on their relationship to the substrate media. The most widely used catalysts are
heterogeneous, mainly due to the massive quantities used in petroleum refinement. The term heterogeneous means that the catalyst and substrates are in two separate phases. In petroleum refinement, the catalyst is fixed to a support while the substrates pass over the catalyst bed as a gas. One of the advantages of using this type of catalyst system is the ability to reuse or recycle the catalyst.44, 51, 69-75 Another advantage is the relatively easy
product separation. However, heterogeneous catalysts are less reactive and selective
when compared to their homogeneous counterparts and also often require elevated
5 temperatures and pressures. In addition to their use in petroleum refinement,
heterogeneous catalysts have been employed for asymmetric epoxidation,51 hydrogenation,73, 75 polymerization,76-78 and Heck coupling.79, 80
The second type of catalyst is homogeneous catalysts, where both the substrate(s)
and catalyst are in the same reaction media. This type of catalyst usually displays better
selectivity and reactivity, as well as lower reaction temperatures and pressures than those
of heterogeneous catalysts.1, 2, 44, 51, 69-75 Although the lack of reusability of the catalyst is
limited due to the challenges presented by the need to separate the catalyst from the
reaction mixture, the excellent catalytic activities and broad applicability of
homogeneous catalysts outweighs this disadvantage. Homogeneous catalysts have been
used for hydroformylation,81-87 hydrogenation,44-48, 88-90 polymerization,3, 12-14, 91-93 epoxidation,49, 50, 53-56 cross-coupling,94-106 hydroamination,7, 22, 26, 40, 107 hydrosilation,88,
108-111 carbonylation,112-114 alkene metathesis,3 and oxidation/reduction.76, 115-121 One further advantage of homogeneous catalysts is the ability to determine key intermediates in a reaction mechanism using a variety of different solution techniques. Although determining intermediates for the heterogeneous catalysts is not impossible, it is much more challenging and less conclusive than with homogeneous catalysts.
Catalysts come in a variety of shapes and sizes. The most prolific type is acid/base catalysts, which play important roles in esterification, condensation, and oxidation reactions.52, 67 Another type of catalyst is organic-based catalysts
(organocatalysts), which have been used in a variety of reactions and do not have a metal
present.115, 122-132 However, the most interesting and broadly applied class of catalysts is
those which contain a metal. Metal catalysts can be used in a variety of reaction media,
6 demonstrate outstanding functional group tolerance, and can be used for a variety of
different transformations. Metal catalysts can be subdivided even further into main
group, early transition/lanthanide and late transition metal catalysts. Main group
catalysts have been used for hydroamination,5, 133 but usually suffer from poor functional
group tolerance. Early transition and lanthanide metal based catalysts are more tolerant of functional groups and can be used for a multitude of catalytic transformations;4, 7, 9-56 however, these catalysts are usually highly sensitive to oxygen and water, making them more difficult to handle and thus less desirable. Late transition metals are not as sensitive to oxygen or water and have been shown to be tolerant to a variety of functional groups in many catalytic reactions, although a significant drawback is their high cost. 7, 41, 59-61, 64,
107, 134-175
I-3: Hydroamination
As countless examples of nitrogen-containing organic molecules can be found in
the pharmaceutical, agricultural, and industrial fields, the synthesis of carbon-nitrogen
bonds is of great importance in organic chemistry.7 Although numerous routes are
known for the formation of carbon-nitrogen bonds, the most efficient and atom-
economical method is the direct addition of amines to unsaturated carbon-carbon bonds,
which cannot be achieved without a catalyst due to the high activation energy barrier
present. Hydroamination is a catalytic process where the nitrogen-hydrogen bond of a
primary or secondary amine is added across a carbon-carbon double or triple bond in an
organic molecule. Because this route utilizes 100% atom economy, it is the most efficient route to amines, imines, and enamines. Even though there are several examples of hydroamination with main group,5, 133, 176, 177 lanthanides,18, 23-28, 30, 33-35, 37, 39, 178-180
7 actinides,9, 10, 181 early7, 15, 16, 19-22, 28, 29, 31, 38, 40, 41, 182, 183 and late transition metals,7, 41, 59-61,
64, 107, 134-175 a general hydroamination reaction applicable to a wide array of substrates
remains elusive.
There exist two types of hydroamination, based solely on the nature of the starting
substrate.7, 21, 22, 32, 41, 42, 61, 64, 139, 143 For intramolecular hydroamination, substrates have an amine moiety tethered through an organic linker to the unsaturated carbon-carbon bond. This type of hydroamination is nearly entropically neutral, which allows intramolecular hydroamination to be more energetically favored. Even though intramolecular hydroamination occurs with both early and late transition metals, as well as lanthanides and actinides, this occurs with two different prevailing mechanisms. In the case of early transition metals, the first step is the formation of either an metal-amido or imido bond with the amine tethered to an unsaturated carbon-carbon bond.6, 24, 179, 180, 182
The unsaturated carbon-carbon bond inserts into the metal-nitrogen bond, forming a carbon-nitrogen bond and a metal-carbon bond (Scheme 5). A second equivalent of the aforementioned amine then protonates the metal-carbon bond, forming a carbon- hydrogen bond and a metal-nitrogen bond, regenerating the active species. For metal- imido catalysts, the catalytic cycle requires two protonation steps, but is otherwise very similar.182 Lanthanides, actinides, and main group elements are all believed to follow the
early transition metal intramolecular hydroamination mechanism.24, 179, 180 For late
transition metals, the first step in intramolecular hydroamination is believed to be the
coordination of the unsaturated carbon-carbon bond to an open coordination site of the
metal center (Scheme 6). 6, 7, 136, 150 Next, nucleophilic attack by the nitrogen generates a carbon-nitrogen bond and a carbon-metal bond. This synthetic intermediate is known as
8 R' R' LnM N H N R n R n R' H N
R n
R' R' LnM N LnM N R n R n
Scheme 5. Intramolecular hydroamination catalyzed by a lanthanide or an early
transition metal. a zwitterionic complex, where the nitrogen carries a positive charge, while the metal center has a negative formal charge. A proton migration from the nitrogen to the carbon attached to the metal center results in product formation in tandem with regeneration of the initial catalyst.
LnM H R N N R
H LnM H N R R N LnM
Scheme 6. Late transition metal catalyzed intramolecular hydroamination.
9 The second type of hydroamination is intermolecular. Unlike its counterpart, the
substrates for intermolecular hydroamination are not tethered, but rather exist as two
independent molecules. Therefore, the many substrates used in intermolecular
hydroamination are both commercially available and relatively inexpensive. Another
advantage of intermolecular hydroamination is that since the amine and unsaturated
carbon-carbon bond moieties are not tethered to one another, the products are not cyclic in nature, substantially increasing the diversity of target products. However, the major drawback of intermolecular hydroamination is a significantly higher entropic effect, which results in the requirement of a more selective and active catalyst or the use of activated substrates.
Similar to intramolecular hydroamination, the mechanisms proposed for intermolecular hydroamination change when different metals are used as the active catalyst. For early transition metals, entry into a catalytic cycle requires the generation of either a metal amido or imido complex. When starting with a metal imido complex, a reversible [2+2] cycloaddition of an alkyne occurs, generating a carbon-metal bond and a carbon-nitrogen bond, as well as reducing the nitrogen-metal bond order by one (Scheme
7).7, 21, 40, 41 Next, an amine protonates the carbon-metal bond, forming a carbon-
hydrogen bond as well as a second metal amido ligand. The initial amido group is then
protonated, yielding the product enamine and regenerating the metal imido catalyst.40, 182,
183 The enamine then tautomerizes into the more thermodynamically favorable imine.
For late transition metals, intermolecular hydroamination is thought to occur through one
of two predominate mechanisms. The first mechanism involves the coordination of an
10 N Ar
R R
H LnM NAr N Ar RR RR
Ar R Ar N L MN R n LnM NHAr RR
H2NAr
Scheme 7. Early transition metal catalyzed intermolecular hydroamination.
unsaturated carbon-carbon bond to the metal center (Scheme 8).6, 7, 164, 173 Next, a
nucleophilic amine attacks the unsaturated carbon-carbon bond, generating a zwitterionic
complex. Proton migration from the ammonium yields the product amine, regenerating
the catalytically active species at the same time. The other, less accepted mechanism is
initiated by the generation of a metal-amido intermediate by the oxidative addition of an
amine to yield amido and hydride ligands (Scheme 9).7, 173, 184 Next, the unsaturated
carbon-carbon bond binds to the metal and inserts into either the metal-nitrogen bond or the metal-hydride bond. The final step is reductive elimination of the product amine.
A third mechanism for intermolecular hydroamination using late transition metals involves the use of allylic intermediates and is generally applied when conjugated
11 LnM R' N R R R'
L M H n L M N R' n R R R'
HNR'2
Scheme 8. Late transition metal catalyzed intermolecular hydroamination by a zwitterionic intermediate.
L M H n
H2NR R' NHR
H H LnM LnM R' NHR NHR
R'
Scheme 9. Intermolecular hydroamination by late transition metal-amide complex utilizing oxidative addition and reductive elimination.
12 systems are used.107, 167 Entry into the catalytic system is attained by the generation of a
metal-hydride (Scheme 10). Once formed, a conjugated carbon-carbon bond inserts into
the metal-hydride, resulting in a metal-allyl species. Nucleophilic attack by an amine
forms a zwitterionic complex, which then undergoes proton migration yielding the
product and regenerating the metal-hydride.
NR'2 LnMH
NHR'2
LnM LnM
HNR'2
Scheme 10. Intermolecular hydroamination of conjugated systems catalyzed by a late
transition metal-hydride.
I-4: Cross-Coupling Reactions
The ability to form carbon-carbon and carbon-heteroatom bonds plays an
important role in modern organic synthesis.2, 94-96, 98, 185-188 These bonds are found throughout society in the form of polymers, pharmaceuticals, fine-chemicals, agrochemicals, and natural products. By using cross-coupling reactions, not only are these bonds formed in high yield, but quite often these reactions can be tuned to set one or more stereocenters. By utilizing catalysts for these reactions, it is often possible to
13 eliminate the need of protecting groups and the use of highly toxic and reactive chemicals such as organotin or organolithium reagents. Over the past fifty years, several groups have been interested in expanding the substrate scope, in addition to lowering catalyst loading and implementing more cost effective bases and solvents for these cross-coupling reactions.79, 80, 94, 97, 98, 189, 190
Suzuki-Miyaura Coupling
The Suzuki-Miyaura reaction is one of the most efficient means of synthesizing biaryl and substituted aromatic compounds, which function as building blocks of polymers, ligands, and a wide range of alkaloids.96-98, 100, 101, 191 Also known as Suzuki coupling, this reaction utilizes an organoboron reagent, RB(OR’)2, where R and R’ can be many functional groups including hydrogen, alkyl, alkenyl, alkynyl, or aryl groups.67, 97,
98 The active catalyst is often a palladium(0) source; however, the precatalyst can also be a palladium(II) source which is reduced under catalytic conditions. Additionally, a base is typically added to help facilitate reduction of the palladium and also aid in the transmetallation step of the catalytic cycle.
The mechanism of Suzuki-Miyaura coupling is thought to occur through one of two very similar routes.98 In the first, oxidative addition of an aryl-halide (Ar-X) to the palladium(0) source occurs, oxidizing the palladium(0) to palladium(II) by the binding of two monanionic ligands Ar- and X- (Scheme 11). Next, transmetallation from the organoboron reagent occurs, replacing the X- ligand with an Ar’- ligand. Of particular note, the ligand replacing the X- ligand can also be an alkyl, alkenyl, or alkynyl group, not merely an aryl substituent. Reductive elimination regenerates the palladium(0) catalyst and forms a carbon-carbon single bond between the two different
14 0 LnPd Ar Ar' Ar X
Ar Ar L Pd n Ln Pd Ar' X
XB(OR)2 Ar'B(OR)2 Scheme 11. General catalytic cycle for Suzuki-Miyaura coupling.
L Pd0 Ar Ar' n Ar X
Ar Ar Ln Pd Ln Pd Ar' X
MOR ROB(OR')2 Ar Ln Pd OR
Ar'B(OR')2 MX
Scheme 12. Alternative mechanism for Suzuki-Miyaura coupling.
15 aryl groups (Ar-Ar’). Alternatively, it has been proposed that the added base replaces
the halide in the palladium’s coordination sphere after oxidative addition of the aryl
halide occurs (Scheme 12). This facilitates transmetallation with the organoboron
reagent. Once again, the final step is reductive elimination of the biaryl compound and
regeneration of the palladium(0) catalyst.
Buchwald-Hartwig Coupling (Aryl Amination)
The formation of carbon-nitrogen bonds is of considerable interest due to the wide use of amines and enamines, especially aryl amines, across many fields of chemistry.
Compounds containing carbon-nitrogen bonds are commonly found in biologically active natural and synthetic products, key reactions in organic chemistry, and throughout the pharmaceutical and fine-chemical industries. Even though there are numerous synthetic methodologies to prepare structurally different anilines, a general reaction, which possesses low catalyst loading, short reaction time, and mild reaction conditions, is highly desired.94, 104-106, 186, 187, 192, 193 Therefore, considerable effort has been devoted
towards the development of catalysts containing a broad substrate scope at mild reaction conditions and temperatures. Aryl amination is an alternate route to aryl amines in lieu of
a robust hydroamination catalyst.
The mechanism of aryl amination has been well studied.94, 189 Starting from
palladium(0), which can be generated in situ from a variety of palladium(II) sources, an
aryl halide is oxidatively added, generating a palladium(II) complex with monoanionic
aryl (Ar) and halide (X) ligands (Scheme 13). Next, an amine coordinates to the
palladium center, followed by deprotonation of the coordinated amine by the added base, which forms the necessary amido ligand. Deprotonation is coupled with the formation of
16 a halide salt. Reductive elimination regenerates the palladium(0) catalyst while forming
the product aryl amine (Ar-NRR’).
Ar NRR' 0 Ar X LnPd
Ar Ar Ln Pd Ln Pd NRR' X
NaX + HOtBu Ar L Pd X n HNRR' NaOtBu HNRR
Scheme 13. Buchwald-Hartwig coupling (aryl amination) mechanism.
I-5: Ligands for Metals
In comparison to traditional coordination complexes, organometallic compounds are usually more covalent in nature and their metals tend to be in a more reduced state.1, 3
Therefore, one role of the ligands used to bind metals in these lower oxidation states is to protect the metal from oxidation reactions. Ligands are commonly broken down into classes based on how many donor atoms they contain and their overall charge.
Commonly, ligands are considered either monodentate (one donor atom) or polydentate
(two or more donor atoms). Ligands of a wide variety of denticity are used throughout organometallic chemistry, and their application is typically directly related to the function(s) of the organometallic compound in which they are bound. Because metals are
Lewis acidic, the overall charge of a ligand is almost always either neutral or anionic.
An important aspect in ligand design is the selection of donor atoms. All ligands
17 bind to metal centers through a σ bond, in which the ligand donates a pair of electrons in
forming a metal-ligand bonding interaction, making the electronegativity of the donor
atom an important consideration. Another important and well studied relationship
between the metal center and the ligand are π interactions. These interactions, formed
by either the donation or acceptance of π electrons between a metal center and a donor
atom, allow for the ability to further control the electrophilicity and nucleophilicity of the metal center. Strong π-acceptor ligands are important in stabilizing metal centers that are in low oxidation states.3 The empty ligand antibonding orbital, π*, will interact with the filled d orbitals of the metal center, generating one filled bonding molecular orbital and one empty antibonding molecular orbital. Since the filled molecular orbital has a significant contribution from the ligand π* orbital, the electron density from the metal center will function to create a stronger metal-ligand bond at the expense of bonding within the ligand. Alkenes and arenes that donate their electron density to a metal center are considered π-donor ligands. Another way to distinguish donor atoms is through hard/soft chemistry. All donor atoms are considered either hard or soft donors in reference to their polarizability.1, 3 Atoms which are easily polarized are considered soft, whereas difficult to polarize atoms are termed hard. Therefore, a row 6 element like platinum would form a stronger bond with an iodide ligand rather than a fluoride ligand, while sodium would form a stronger bond with chloride compared to bromide.
A final aspect of ligand design is the implementation of asymmetry in the ligand framework.194 Typically, symmetrical ligands like triphenylphosphine,
diphenylphosphinoethane or tetramethylethylenediamine are relatively easily synthesized
and cost effective. However, if one desires any type of stereocontrol, these ligands
18 perform rather poorly due to their symmetry. Asymmetric ligands have the ability to
control the manner in which a substrate binds to a metal center or dictate how attack on a
substrate bound to the metal center occurs.94, 137, 195-203 Asymmetric ligands provide
stereocontrol by either blocking coordination sites, thus preventing substrates from
coordinating to some regions around the metal center, or by dictating substrate binding
energetically by diastereomeric effects at the metal center.204-209 In general, chirality can
be controlled by using a chiral metal complex (enantioselective control) or by using a
single diastereomer of a metal complex (diastereomeric control).
Another advantage of using an asymmetric ligand is the option to employ a ligand
which is hemilabile.210-215 A hemilabile ligand has the ability to coordinate/decoordinate
a metal center while in solution in a controlled and reproducible manner. One of the
benefits of hemilabile ligands is their ability to stabilize catalytic intermediates as well as
open new coordination sites for substrate binding. Hemilability is created by using two
very different donor atoms in a polydentate ligand set, such as phosphorus-oxygen,190 phosphorus-nitrogen,190, 216, 217 phosphorus-sulfur,218, 219 and nitrogen-oxygen220 ligand
systems.
I-6: P-N Ligands
One of the most prevalent types of asymmetric polydentate ligand systems is the
group that is composed of phosphorus and nitrogen donor atoms.77, 205-208, 217, 221-240 By
employing a hard donor, nitrogen, with a much softer donor, phosphorus, this series of
ligands has been successfully complexed with not only late transition metals, but also
with early transition and lanthanide metals. The early transition metals favor the nitrogen
donor over the phosphorus even though the phosphorus is a better σ donor, due to the
19 hardness of these metals and the higher electronegativity of the nitrogen donor atom. The opposite can be said for late transition metals, who favor the phosphorus donor atom.
The electronic differences between the phosphorus and nitrogen donor atoms help to create control over how a substrate binds to a metal center. Another advantage of polydentate P-N ligand systems is their ability to form strong chelate rings. Chelate rings, typically 4, 5, 6, 7, or even 8 atoms long, increase the stability of the metal complex. Additionally, if the chelate ring is unsaturated, some of the metal’s electron density can be dispersed throughout the ring through backbonding, increasing the overall
stability of the complex.
P-N ligands are usually either neutral or anionic and have been synthesized with a
wide array of substituents on both the phosphorus and nitrogen donors. Anionic P-N
ligands (Figure 1A) were first discovered in the early 1990’s and have been used as ligands with early and late transition metals.77, 221-226 Arnold and coworkers complexed
several polydentate ligands, which contained an anionic nitrogen donor, a neutral
nitrogen donor and two neutral phosphorus donors, with various metals and observed that
the phosphorus donor was often uncoordinated to the metal center, which they attributed
to steric hindrance.225 They also observed that zirconium preferentially bound a nitrogen
donor over a similar sized phosphorus donor.225 Four types of neutral P-N ligands will
now be overviewed. The first subclass is distinguished by the incorporation of a
pyridinyl nitrogen donor (Figure 1B).227, 228 These ligands have been used in a variety of
catalytic reactions, including allylic alkylation and hydroboration. Another set of neutral
P-N ligands utilize a ferrocenyl framework.229 By using this backbone, the subsequent ligands are less air and water sensitive. Moreover, chirality is easily installed on the
20 nitrogen moiety prior to phosphination of the cyclopentadienyl ring, and this chirality has
a direct effect on asymmetric catalysis, as noted in the cases of hydrogenation,
hydrosilation, and allylic alkylation. Phosphinooxazolines (PHOX) contain an
unsaturated backbone connecting phosphine and imine donor groups (Figure 1C).205, 208,
228, 230-234 The distinguishing feature of PHOX ligands is that the nitrogen donor is part of
a 5-membered oxo-containing (oxazoline) ring. Substitution of this ring at the 3-position
allows for the generation of a chiral ligand, which has been used as an ancillary ligand in
Heck coupling, allylic alkylation and hydrogenation. The final subclass of neutral P-N
ligands is 3-iminophosphines. Similar to PHOX ligands, 3-iminophosphine ligands
contain an unsaturated backbone, but unlike PHOX ligands, the imine moiety is not part
of a ring system (Figure 1D).
R' R2P R' R' PR'NR R2P N P NR 2 R2P N 2P NR 2 N SiMe2 O
A B C D
Figure 1. Various P-N ligands (A = Anionic P-N; B = Pyridine-based P-N; C =
PHOX; D = 3-Iminophosphine).
3-Iminophosphine ligands have been used throughout organometallic
chemistry.206, 207, 217, 235-240 One of the greatest advantages these ligands have over their
P-N counterparts is their ease of synthesis from cheap, commercially available sources.
Since the imine moiety is not part of a ring structure, as in the PHOX ligands, the imine
can accommodate not only sterically bulky substituents to help protect the reactive metal
center, but also chiral substituents. A recent advancement in the 3-iminophosphine
21 ligand framework is our recent incorporation of an alkenyl backbone (as presented in this
dissertation), which allows for substitution of the backbone beyond that of an aromatic
ring.239-241 Finally, this ligand series has been part of a variety of catalytic reactions
including Heck coupling,206 polymerization,238 Stille coupling,207, 235, 236 and hydroamination.239
22
Chapter 2:
──────────────────────────────
Synthesis, Isolation, and Characterization of α,β-Unsaturated
3-Iminophosphines
──────────────────────────────
23 II-1: Introduction
Phosphines are attractive ligands for late transition metal-based catalyst design;
the strong bonds formed between phosphorus and late metals provide for the stabilization
of reactive metal centers commonly found as intermediates in catalytic cycles.194 For
example, the use of phosphine ligands in palladium catalysis has circumvented the
formation of palladium black, one of the most common catalyst decomposition pathways
observed with this metal.2 Additionally, phosphine-ligated metal complexes often
display excellent air and water stability, avoiding phosphine oxide formation due to the
strong interaction between the phosphorus lone pair and the metal center.194 As current
synthetic routes available for the synthesis of substituted phosphines limit the specific
steric and electronic properties of phosphine-based ligands somewhat, the discovery of
new and general reaction schemes for phosphine synthesis remains an important pursuit
in the advancement of phosphine-based catalysis.
The development of phosphine chemistry has drawn much attention because
phosphines have been successfully used as ancillary ligands for a variety of catalytic
reactions including hydroamination,42, 137, 168 hydrogenation,195, 204 allylic amination,196-199 cycloaddition205 and cross-coupling.79, 94, 98, 190, 200, 206, 207, 228 While aiming to achieve
high catalyst activity in the above reactions, control of molecular chirality is invaluable
for pharmaceutical applications and fine-chemical syntheses.201, 202 Often, catalytic
control of product chirality can be accomplished through the use of chiral metal
complexes (enantioselective control) or by using specific diastereomers of metal
complexes displaying an even lower molecular symmetry (diastereomeric control). The
use of chiral phosphines has played a strong role in enantioselective control, whereas
24 unsymmetric phosphine-containing chelating ligands (using two phosphorus donor atoms
or one phosphorus and one nitrogen atom) are important for diastereomeric control. The
formation of a single diastereomer by using mixed chelates is also highly valuable as it
allows for alternate mechanistic pathways for asymmetric catalysis.
Thus far, bidentate, chiral diphosphine-ligated catalysts have realized success in a
wide variety of asymmetric catalytic reactions.94, 137, 195-197, 199-203 The biggest limitations
of these catalysts relate to substrate scope and catalyst activity.201, 202 An alternate
approach to asymmetric catalysis involves bidentate ligands in which each donor atom
has unique steric and electronic properties. Asymmetric ligands of this type have
displayed hemilability (partial decoordination),210 resulting in new and useful mechanistic
pathways.204-209 3-Iminophosphine ligands, which contain a phosphine moiety tethered to an imine through an o-phenylene backbone, have been investigated previously, and their palladium complexes serve as catalysts for a variety of reactions.206, 207, 217, 235-240 The
success of this ligand series led to the belief that incorporation of an α,β-unsaturated
backbone may display improved catalytic activity.
The new class of 3-iminophosphine ligands described in this dissertation contain
an α,β-unsaturated alkenyl backbone, which distinguish these species from other known
phosphine-imine ligands that have been constructed based on ortho-substituted phenyl
groups. These ligands contain features of two prominent ligand classes: β-diketiminates
and phosphinooxazolines. β-Diketiminates, when used as ancillary ligands in late
transition metal catalysis, employ steric bulk to help shield reactive metal centers and
provide stability for reactive intermediates.204 Phosphinooxazolines help stabilize
reactive intermediates and reactive metal centers through a combination of steric
25 protection and strong σ-donation from the phosphorus donor atom.107, 204, 228, 242, 243 α,β-
Unsaturated 3-iminophosphine ligands have significant electronic asymmetry, utilizing a soft tertiary phosphine that exhibits a high affinity for late-transition metals in tandem with a much more weakly coordinating aldimine.
II-2: Results and Discussion
1st Generation 3-Iminophosphine Ligands
A wide range of aliphatic α,β-unsaturated 3-iminophosphines was synthesized
from commercially available, inexpensive precursors using a new three-step, high-
yielding protocol. This methodology employs the Vilsmeier-Haack reagent to produce
aliphatic α,β-unsaturated β-chloroaldehydes, which are reacted with a variety of primary
amines under Schiff-base condensation conditions to yield aliphatic α,β-unsaturated β-
chloroimines.244 The final conversion to the desired aliphatic α,β-unsaturated 3-
iminophosphines is achieved by either a late transition metal-catalyzed coupling reaction
or the direct substitution of chloride using an alkali metal phosphide.
The Vilsmeier-Haack reagent, generated in situ, is commonly employed to
convert a ketone with an enolizable α hydrogen (through its enol tautomer) into a vinyl
chloride while simultaneously adding an iminium group, thus extending the carbon
framework by one unit.245 Herein, the reaction of the Vilsmeier-Haack reagent with
acetophenone, pinacolone, or propiophenone was used to generate the corresponding
aliphatic α,β-unsaturated β-chloroaldehydes after basic aqueous workup (Scheme 14).
By using optimized conditions, compound 1a was produced in 74% yield with high
diastereoselectivity (Z/E 9:1), as previously reported. The use of pinacolone produced
the related product with a tert-butyl group in place of the phenyl group and yielded only
26 the Z isomer 1b. In contrast, the use of propiophenone produced almost exclusively the E
diastereomer of 1c (E/Z 9:1), due to the enhanced stabilization of the enol intermediate.244
These compounds formed the backbone for our synthesis of a wide range of aliphatic α,β- unsaturated 3-iminophosphines.
Schiff base condensation of 1a-c readily converted these aldehydes to aldimines with various primary amines, including tert-butylamine, aniline and 2,6-dialkylanilines
(Scheme 14).246 The Z isomers of compounds 2a-e were readily separated from the trace
amounts of E diastereomers produced from the condensation of the small amount of E-1a initially present and were isolated in 65-86% yield (Table 1). Imines 2f-j were found to produce Z diastereomers, as present in the initial aldehyde 1b. This group of imines (2a- j) had very similar 1H NMR resonances for their 1-aza-1,3-butadiene backbones (Z
isomers in all cases), with minor differences attributable to the electronic effects of the
substituents present. Excluding 2l, the condensation reactions to produce 2k-o proceeded
much slower due to the methyl substitution of the backbone. For imine 2l, the workup
allowed for isolation of exclusively the E diastereomer, with the small amount (~10%) of
Z isomer readily removed by recrystallization. For 2m-o, attempted distillation to
remove the starting aldehyde and residual unreacted anilines from the final products led
to thermal isomerization of the substituted vinyl group, resulting in approximately a 3:1
Cl Cl O 1 3 1 3 1. PCl5, DMF R O H2NR R NR 1 2 2. H O (s) Et O R CH2R 2 2 R2 R2 1a: R1 = Ph; R2 = H (74%) 2a-o 1b: R1 = tBu; R2 = H (84%) 1 2 1c: R = Ph; R = Me (70%)
Scheme 14. Synthesis of aliphatic α,β-unsaturated β-chloroimines (2a-o).
27 Table 1. Schiff base condensation of aliphatic α,β-unsaturated β-chloroaldehydes (1a-
c) to form α,β-unsaturated β-chloroimines (2a-o)a
Entry R1 R2 R3 Product Temp [°C] Time [h] Yield[%]b
1 Ph H tBu 2a 0 14 86% 2 Ph H Ph 2bc 0 14 65%
3 Ph H 2,6-Me2Ph 2c 0 14 72%
4 Ph H 2,6-Et2Ph 2d 0 14 71% i 5 Ph H 2,6- Pr2Ph 2e 0 14 78% 6 tBu H tBu 2f 0 14 82% 7 tBu H Ph 2gd 0 14 4d (62%)
t 8 Bu H 2,6-Me2Ph 2h 0 14 88%
t 9 Bu H 2,6-Et2Ph 2i 0 14 90% t i 10 Bu H 2,6- Pr2Ph 2j 0 14 87% 11 Ph Me tBu 2k 25 110 94% 12 Ph Me Ph 2l 25 14 79%
13 Ph Me 2,6-Me2Ph 2m 25 110 81%
14 Ph Me 2,6-Me2Ph 2n 25 110 84% i 15 Ph Me 2,6- Pr2Ph 2o 25 110 77%
aReaction conditions: 1.1 eq amine, 1.0 eq 1a-c, 30 mL of diethyl ether. bIsolated
yields. c90 mL of diethyl ether. dImine 2g was observed as a component of the crude
products, but was converted to the addition product 4 in high yield upon workup. ratio of E/Z isomers. Thus, the crude products were used for subsequent reactions (E/Z ratio of about 9:1). The 1H NMR spectra for E imines 2k-o were significantly different from those of the Z imines (2a-j), but trends in the resonances were consistent within this group of E imines. Imines 2c-e, h, j, and l were isolated as solids by recrystallization and
28 the solid state structures of these compounds were determined by X-ray crystallography
(Figures 2-4). Overall, these solid state structures showed that the bond lengths and angles varied little throughout this series; all bond lengths and angles were typical for organic compounds of this type.247
Several aspects of the syntheses of imines 2a-o merit further comment. In general, undesirable products were formed when these reactions were run under high concentrations, whereas the reactions proceeded very slowly if they were carried out too dilute. The optimized conditions described herein provide a reasonable reaction time while minimizing the amount of byproducts formed. The reactions involving unsubstituted aniline were especially challenging and required very careful control of conditions and subsequent handling. The shelf life of product 2b was limited to about 48 h when stored under ambient atmosphere; however, it was stable for several months
Figure 2. ORTEP diagram (50% thermal ellipsoids) of PhCCl=CHCH=N(2,6-
i Pr2C6H3) (2e). Hydrogen atoms omitted for clarity. Bond lengths (in Å): N1-C1 =
1.273(2), C1-C2 = 1.449(2), C2-C3 = 1.335(2), C3-Cl1 = 1.745(1). Bond angles (in
deg): C1-N1-C10 = 116.7(1), N1-C1-C2 = 121.2(1), C1-C2-C3 = 125.1(1), C2-C3-
Cl1 = 119.3(1).
29 Figure 3. ORTEP diagram (50% thermal ellipsoids) of tBuCCl=CHCH=N(2,6-
i Pr2C6H3) (2j). Hydrogen atoms omitted for clarity. Bond lengths (in Å): N1-C1 =
1.271(2), C1-C2 = 1.463(2), C2-C3 = 1.323(2), C3-Cl1 = 1.753(2). Bond angles (in
deg): C1-N1-C8 = 118.4(1), N1-C1-C2 = 120.3(1), C1-C2-C3 = 126.8(1), C2-C3-Cl1
= 118.9(1).
under nitrogen. Moreover, imine 2g could be observed in the crude reaction mixture, but
its isolation proved untenable. Attempted isolation by crystallization proved futile
because 2g reacts with leftover aniline from the condensation reaction to yield the
addition product 4 (Scheme 15). The identity of 4 was confirmed by NMR spectroscopy,
high-resolution mass spectrometry, and X-ray crystallography (Figure 5).
The initial approach for the conversion of aliphatic α,β-unsaturated β- chloroimines (2a-o) to phosphines involved treatment with lithium diphenylphosphide
NH2Ph Cl t H2NPh Bu Cl tBu NPh NPh 2g 4
Scheme 15. Attempted isolation of 2g results in addition of aniline to yield 4.
30 Figure 4. ORTEP diagram (50% thermal ellipsoids) of PhCCl=CMeCH=NPh (2l).
Hydrogen atoms omitted for clarity. Bond lengths (in Å): N1-C1 = 1.281(2), C1-C2
= 1.463(2), C2-C3 = 1.350(2), C3-Cl1 = 1.744(1). Bond angles (in deg): C1-N1-C11
= 117.9(1), N1-C1-C2 = 120.9(1), C1-C2-C3 = 118.6(1), C2-C3-Cl1 = 118.8(1).
(LiPPh2). It was anticipated that 2a-o would undergo phosphide addition followed by rapid chloride elimination, effecting the conversion of the chloro group to a diphenylphosphine. Attempts to use this methodology for imines 2a-e proved unsuccessful initially because multiple, unidentified phosphorus-containing products were observed by 31P NMR spectroscopy. Similar results were observed with sodium
diphenylphosphide (NaPPh2). Addition of diphenylphosphine (HPPh2) in the presence of
triethylamine or pyridine also yielded multiple products. In contrast, when
diphenyltrimethylsilylphosphine (Ph2PSiMe3) was used as the phosphorus source, no
reaction was observed at all.
Previous work by Beletskaya and coworkers has shown that cross-coupling of
diphenyl(trimethylsilyl)phosphine with vinylic halides can be effected using either nickel
or palladium catalysts with retention of stereochemistry.248, 249 The use of late transition
metal cross-coupling reactions for conversion of the aliphatic α,β-unsaturated β-
31 Figure 5. ORTEP diagram (50% thermal ellipsoids) of tBuCN(H)Ph=CHCH
=N(H)+Ph (4). Hydrogen, chloride and solvent atoms omitted for clarity. Bond
lengths (in Å): N1-C1 = 1.324(3), C1-C2 = 1.372(2), C2-C3 = 1.410(3), C3-N2 =
1.319(3). Bond angles (in deg): C1-N1-C8 = 127.4(2), N1-C1-C2 = 120.9(2), C1-
C2-C3 = 130.2(2), C2-C3-N2 = 126.7(2), C3-N2-C14 = 126.4(2).
chloroimines (2a-e) in a stepwise fashion to more fully understand the underlying chemistry in this process was investigated. Initially, compound 2d was added to a
palladium(0) source, tetrakis(triphenylphosphine)palladium(0), at 0°C in toluene
(Scheme 16). Oxidative addition to the metal center afforded a palladium(II) complex, 5,
as well as two equivalents of free triphenylphosphine, which were readily removed by
subsequent pentane washes. The 31P NMR spectrum for 5 showed a single resonance at δ
= 24.3 ppm, indicating that the two remaining triphenylphosphine ligands were
PPh3 Ph Cl Pd(PPh3)4 Cl Pd Ph NAr PPh -2 PPh3 3 NAr Ar = 2,6-Et2C6H3 2d 5 Scheme 16. Oxidative addition of 2d to Pd(0).
32 equivalent and thus trans to one another. Additionally, the narrow line width observed implied that 5 was not fluxional in solution. To confirm its connectivity, yellow crystals of 5 were grown from a solution of toluene layered with pentane at room temperature and its X-ray crystal structure was solved (Figure 6). The triphenylphosphine ligands were indeed trans to one another, confirming the NMR spectroscopic assessment.
Furthermore, the stereochemistry of the carbon-carbon double bond was retained in the Z
diastereomer, with the imine carbon trans to the phenyl substituent.
To investigate the metal-mediated phosphine coupling step, one equivalent of
diphenyl(trimethylsilyl)phosphine was added to 5, and the reaction was monitored by 1H and 31P NMR spectroscopy (Scheme 17). After 10 min, the doublet in the 1H NMR
Figure 6. ORTEP diagram (50% thermal ellipsoids) of 5. Hydrogen atoms omitted
for clarity. Bond lengths (in Å): N1-C1 = 1.273(3), C1-C2 = 1.445(3), C2-C3 =
1.354(3), Pd1-C3 = 2.017(2). Bond angles (in deg): P1-Pd1-P2 = 176.2(1), C3-Pd1-
Cl1 = 177.4(1), C1-C2-C3 = 122.6(2), N1-C1-C2 = 123.4(2), N1-C1-C2-C3 =
179.2(2).
33 spectrum at δ = 0.138 ppm corresponding to the methyl groups of
diphenyl(trimethylsilyl)phosphine250 was replaced by a sharp singlet representative of
chlorotrimethylsilane (Me3SiCl, δ = 0.175 ppm). Pronounced shifts for the alkenyl backbone resonances in the 1H NMR spectrum, as well as changes in the 31P NMR
spectrum, were also observed. Very similar results were observed when a more
nucleophilic phosphine source, lithium diphenylphosphide, was used. It was postulated
that in both cases substitution of the chloro ligand for a diphenylphosphide ligand
occurred at the palladium, with concomitant loss of chlorotrimethylsilane and lithium
chloride, respectively. The resultant complex was then unstable with respect to reductive
elimination, which occurred through the rapid formation of a carbon-phosphorus bond.
The final product (6) from this reaction sequence was observed spectroscopically, and its
31P NMR spectrum consisted of two broad resonances at δ = 24.5 and 25.8 ppm, which
integrated in a ratio of 2:1. The broad peaks observed are indicative of fluxionality in
solution, which was attributed to rapid coordination/decoordination of the phosphine
ligands. The 2:1 ratio of ligands agrees well with the two triphenylphosphine ligands
present for each equivalent of 3-iminophosphine formed. When purification of 6 by
recrystallization was attempted, the only isolated compound was
PPh3 Ph Ph Ph3P Ph Cl Pd Ph2PX Pd P
PPh3 Ph3P -XCl Ph NAr NAr Ar = 2,6-Et2C6H3 5 X = Li, SiMe3 (6) Scheme 17. Substitution of chloride with phosphide results in rapid reductive
elimination.
34 tetrakis(triphenylphosphine)palladium(0), a low solubility material that was readily generated by the ligand coordination/decoordination processes occurring in solution.
Given that the set of reactions utilized to produce 5 and 6 resulted in the regeneration of phosphine-coordinated palladium(0) species in solution, it was believed that this carbon-phosphorus coupling reaction might be possible using only a catalytic amount of palladium(0) reagent (Table 2). To investigate this reaction catalytically, it was important to use diphenyl(trimethylsilyl)phosphine as the phosphine source because it was previously found to be inert towards compounds 2a-e, unlike diphenylphosphine, lithium diphenylphosphide, and sodium diphenylphosphide. Initially,
Table 2. Metal-catalyzed cross-coupling of aliphatic α,β-unsaturated β-
chloroimines with diphenyl(trimethylsilyl)phosphinea
Entry Reactant Catalyst Temp [oC] Time [h] Conversion[%]c
1 2d Pd(PPh3)4 120 172 60
2 2d Ni(PPh3)4 90 14 21
3 2a Ni(COD)2 120 14 >99
4 2b Ni(COD)2 50 14 >99
5 2c Ni(COD)2 70 14 >99
6 2d Ni(COD)2 90 14 85
7 2e Ni(COD)2 130 14 90
8 2f Ni(COD)2 130 14 <5
9 2f Ni(COD)2 130 158 <5 b 10 2f Ni(COD)2 110 38 45
11 2k Ni(COD)2 130 158 <5
a Reaction conditions: 1.0 eq 2a-f or 2k, 1.2 eq Ph2PSiMe3, 5 mol% catalyst,
b c 1 50 mL of toluene. 10 mol% Ni(COD)2. Observed by H NMR.
35 tetrakis(triphenylphosphine)palladium(0) was employed as a catalyst for this coupling,
but the reaction proceeded very slowly. To achieve faster reaction times, alternative
nickel(0) sources were investigated. The use of tetrakis(triphenylphosphine)nickel(0) as
the metal catalyst provided better results than the analogous palladium(0) complex due to
the increased reactivity of the nickel-ligand bonds. Ultimately, it was found that replacing triphenylphosphine with 1,5-cyclooctadiene (COD) as the auxiliary ligand
increased the reaction rate dramatically because triphenylphosphine forms very stable
metal-phosphorus bonds due to its strong σ donation, whereas 1,5-cyclooctadiene forms
weak metal-alkene bonds by a π-interaction. Thus, catalytic amounts of bis(1,5-
cyclooctabidene)nickel(0) proved to be the most time and cost efficient means to convert
imines 2a-e to the related 3-iminophosphines 3a-e.
After installation of the diphenylphosphino group into the 3-iminophosphines 3a-
e, determination of the diastereomeric configuration of these trisubstituted alkenes proved
to be relatively challenging. Simple coordination chemistry was employed as one means
for determination of the alkene stereochemistry in 3a-e. Thus, phosphine 3b was readily
coordinated to palladium(II), supplied as the (allyl)palladium(II) chloride dimer, to
produce 7 (Scheme 18). X-ray quality crystals of this complex were grown from a
solution of tetrahydrofuran layered with pentane at room temperature. The crystal
Ph Cl Ph Ph Ph P P Pd 0.5 [(allyl)PdCl]2 Ph Ph
NPh NPh 3b 7
Scheme 18. Coordination of 3b to [(allyl)PdCl]2.
36 structure of 7 displayed a square-planar palladium species with the 3-iminophosphine
ligand bound through only the phosphorus (Figure 7). This structure allowed for
definitive assignment of the 3-iminophosphine diastereomer, which was surprisingly
found to be the E isomer (phosphorus atom trans to the imine). Normally, reductive elimination is expected to proceed with retention of configuration, implying that in this case, the operable reaction mechanism may be more complicated than initially anticipated. The isomerization proved to be general, leading to isolation of exclusively the E diastereomers for compounds 3a-e.
Figure 7. ORTEP diagram (50% thermal ellipsoids) of (C3H5)(3b)PdCl (7).
Hydrogen atoms omitted for clarity. Bond lengths (in Å): C1-N1 = 1.278(3), C1-C2
= 1.451(3), C2-C3 = 1.350(3), C3-P1 = 1.824(2), P1-Pd1 = 2.310(1), Pd1-Cl1 =
2.368(1), Pd1-C30 = 2.122(2), Pd1-C28 = 2.185(2). Bond angles (in deg): N1-C1-C2
= 120.0(2), C1-N1-C10 = 119.1(2), C1-C2-C3 = 123.5(2), C2-C3-P1 = 119.4(2), P1-
Pd1-Cl1 = 93.1(1), C30-Pd1-C28 = 68.1(1), C30-C29-C28 = 129.6(4).
To help elucidate the causes for the alkene isomerization observed in the coupling leading to 3a-e, various reaction conditions were investigated. By performing the
37 reaction in the absence of light, it was found that a significant amount of the Z isomer was formed, with an almost 1:1 ratio of Z/E being the highest amount of Z in any attempt
(3d). Even in the absence of light, increasing the reaction times led once again to the production of more E diastereomer at the expense of the Z isomer. The isolated E isomer did not isomerize to the Z isomer under any conditions tested, such as varying light, temperature, or the presence/absence of metal catalysts. Thus, it was concluded that the
E diastereomer of 3-iminophosphines 3a-e is the thermodynamic product of this reaction and an effective synthesis of the Z diastereomer would require a different synthetic route.
An alternative synthetic route which favored exclusive formation of the Z isomer was to react the aliphatic α,β-unsaturated β-chloroimine with lithium diphenylphosphide in extremely dilute solution at very cold temperatures (Table 3). 2d was reacted with a slight excess of lithium diphenylphosphide at -78°C in 80 mL of toluene to yield the corresponding 3-iminophosphine, which adopted the Z-diastereomer. A very slow gradual warming to room temperature was needed to control the stereochemistry around the carbon-carbon double bond of the vinylic backbone. Moreover, if the reaction was warmed to room temperature by removal of the acetone/dry ice bath, the reaction formed the E diastereomer predominately, as well as other unidentified products.
In the case of imines 2f-o, metal-catalyzed cross-coupling of the vinyl chloride with diphenyl(trimethylsilyl)phosphine was ineffective, with little or no conversion to the desired 3-iminophosphine products. Fortunately, the use of the initially proposed addition-elimination sequence by direct reaction with lithium diphenylphosphide proved to be a very successful means for the synthesis of these imines (Table 3). For the syntheses of 3f-j, each of the aliphatic α,β-unsaturated β-chloroimines was added to a
38 Table 3. Conversion of aliphatic α,β-unsaturated β-chloroimines
(2a-o) to 3-iminophosphines (3a-o)a Ph Cl Ph R1 NR3 A P R3 B R1 N R2 R2 2a-o 3a-o
Entry Product Temp [°C] Time [h] Method Yield[%]b
1 3a 110 14 A 75 2 3b 110 14 A 71 3 3c 110 14 A 61 4 3d 110 14 A 69 5 3d -78 14 B 58 6 3e 110 14 A 74 7 3f -78 14 B 57 8 3g -78 14 B N/Ac 9 3h -78 14 B 67 10 3i -78 14 B 41 11 3j -78 14 B 44 12 3k -78 144d B 63 13 3l -78 14 B 52 14 3m -78 144 d B 48 15 3n -78 144 d B 58 16 3o -78 144d B 71 a Reaction conditions (Method A): 1.0 eq 2a-e, 1.2 eq Ph2PSiMe3, 5 mol% Ni(COD)2, 30 mL of toluene. Reaction conditions (Method B):
b c 1.0 eq 2f-o, 1.3 eq Ph2PLi, 20 mL of toluene. Isolated yield. 2g was unavailable; thus, 3g was not attempted. dReaction was stirred at ambient temperature for 130 hours, after 14 h at -78°C.
39 slight excess of lithium diphenylphosphide at -78°C and slowly allowed to warm to 0°C.
A similar approach was used for 3k-o, but the reaction time was considerably longer in
most cases. The ratio of 3-iminophosphine diastereomers was highly dependent on the
temperature and concentration at which the addition occurred, and a select number of
examples demonstrated the formation of only a single isomer. When two isomers were
generated, additional heating after the reaction was complete did not lead to product
isomerization; no change in the E/Z ratio was observed. Since it was not possible to
fully isolate a single diastereomer of the β-chloroimines 2m-o, the crude materials were
used in the addition-elimination sequence to produce 3m-o. In all cases, product workup
led to isolation of the primary products as clean, predominately single diastereomers.
Confirmation of the diastereomeric assignments in 3f-j was achieved by crystallization of
the unmetallated phosphine (Figure 8). X-ray quality crystals of 3f were grown from
pentane, and the crystal structure confirmed the product as the Z diastereomer (the imine
moiety is cis to the diphenylphosphine and trans to the tert-butyl group). The N1-C1 and
C2-C3 bond lengths are consistent with typical double bonds, and the C1-C2 bond length
was comparable with related species.140, 231
Overall, the syntheses of 3-iminophosphines 3a-o proceeded readily with a wide range of substituents. For the β-phenyl-β-chloroimines 2a-e, phosphination was accomplished by using a late transition metal-catalyzed cross-coupling reaction, whereas the remaining β-chloroimines 2f-o were readily phosphinated by a direct addition- elimination sequence. The 3-iminophosphines 3a-e were isolated as E diastereomers
from the cross-coupling reaction and Z diastereomers from the direct phosphination route
and exhibited 31P NMR resonances near δ = 5 ppm and δ = -8 ppm, respectively.
40 Products 3f-j were produced as exclusively Z diastereomers with 31P NMR resonances near δ = -20 ppm. Finally, 3-iminophosphines 3k-o, with methyl branches in their backbones, were isolated as pure E diastereomers exhibiting 31P NMR resonances near δ
= -7 ppm. These resonances are representative of the differing electronic contributions from the alkene substituents as well as the diastereomeric configurations of the compounds isolated.
Figure 8. ORTEP diagram (50% thermal ellipsoids) of 3f. Hydrogen atoms are
omitted for clarity. Bond lengths (in Å): N1-C1 = 1.274(2), C1-C2 = 1.465(2), C2-
C3 = 1.344(2), C3-P1 = 1.847(2). Bond angles (in deg): C1-N1-C8 = 121.0(2), N1-
C1-C2 = 117.7(2), C1-C2-C3 = 129.5(2), C2-C3-P1 = 125.9(1).
2nd Generation 3-Iminophosphine Ligands
In an attempt to synthesize single diastereomers of the 3-iminophosphine ligand series, cyclic ketones were investigated. Because the enolizable α hydrogen is part of a ring system, only one diastereomer should be observed. Moreover, the ring system will also allow for a broader range of phosphinating reagents and conditions to be used.
Another feature of using a cyclic ketone is the reduction of steric bulk next to the phosphine moiety, allowing for the possibility to incorporate more sterically demanding
41 phosphines. Finally, stereocenters could be implemented into the ring which may lead to
asymmetric product control during catalysis.
In a similar manner to how the 1st generation ligands were synthesized, either
cyclopentanone or cyclohexanone was reacted with a Vilsmeier-Haack reagent to
generate the corresponding alicyclic α,β-unsaturated β-chloroaldehyde (Scheme 19).251
By using optimized conditions, compound 1d was produced in 76% yield. Replacement of cyclopentanone by cyclohexanone afforded compound 1e, which was produced in 90% yield, slightly higher than previously reported.251 These aldehydes are unstable over 24 h
and therefore it was perilous to attempt to obtain high-resolution mass spectra data or
elemental analysis on these intermediates. Compounds 1d-e form the backbone of a wide
range of alicyclic α,β-unsaturated 3-iminophosphines.
O Cl Cl 1. POCl3, DMF O H2NR NR
2. H2O (s) Et2O nn n 1d: n = 1 (76%) 2p-z 1e: n = 2 (90%)
Scheme 19. Synthesis of alicyclic α,β-unsaturated β-chloroimines (2p-z).
The Schiff-base condensation of 1d-e readily converted these aldehydes to their
respective aldimines in very high yields with a wide variety of primary amines, including
alkyl and aryl amines (Scheme 19; Table 4). Compounds 2p-z were isolated exclusively
as Z diastereomers and displayed similar 1H and 13C resonances for their alkenyl
backbone resonances with only minor differences attributable to the differing electronic
and steric effects of the substituents present. Moreover, compounds 2p-z were thermally unstable, decomposing within 24 h of isolation at room temperature and 72 h at -25°C.
However, it should be noted that these compounds were stable for up to two weeks prior
42 Table 4. Schiff base condensation of alicyclic α,β-unsaturated β-chloro
aldehydes to form alicyclic α,β-unsaturated β-chloroimines (2p-z)a
Entry n R Product Yield[%]b
1 1 tBu 2p 97
2 1 2,6-Me2Ph 2q 96
3 1 2,6-Et2Ph 2r 94
i 4 1 2,6- Pr2Ph 2s 97 5 1 4-tBuPh 2t 91
6 1 CH2Ph 2u 94 7 2 tBu 2v 84
8 2 2,6-Me2Ph 2w 92
9 2 2,6-Et2Ph 2x 96 i 10 2 2,6- Pr2Ph 2y 98
11 2 CH2Ph 2z 93 aReaction conditions: 1.1 eq. amine, 1.0 eq. 1d-e, 10 mL diethyl ether,
4Å molecular sieves. bIsolated yields. to isolation. Because of their thermal instability, distillation to remove excess amine and unreacted aldehyde resulted in a reddish-black hard polymer like substance. Therefore, compounds 2p-z were used without further purification for the proceeding phosphination reactions. Compounds 2p-z displayed diastereotopic methylene protons of the alkenyl ring, resulting in overlapping triplets of doublets; however, only a few of these compounds demonstrated the splitting pattern clearly enough to be fully resolved.
In order to synthesize 3-iminophosphines 3p-z, which have either a cyclopentenyl or cyclohexenyl ring in their alkenyl backbone, compounds 2p-z were reacted with either sodium or lithium diphenylphosphide (Table 5). These compounds produced single
43 Table 5. Conversion of alicyclic α,β-unsaturated β-chloroimines
(2p-z) to 3-iminophosphines (3p-aa)a
Cl R R'2P N NR C, D, or E
nn 2p-z 3p-aa
Entry R’ Product Method Yield[%]b
1 Ph 3p C 70 2 Ph 3p D 62 3 Ph 3q C 62 4 Ph 3r C 59 5 Ph 3s C 70 6 Ph 3t C 62 7 Ph 3u C 82 8 Ph 3v C 82 9 Ph 3w C 52 10 Ph 3x C 54 11 Ph 3y C 77 12 Ph 3z C 69 13 tBu 3aa E 72
a Reaction Conditions (Method C): 1 eq. 2p-z, 1.2 eq. Ph2PLi,
Toluene, -78°C, 14 h. Reaction Conditions (Method D): 1 eq. 2p,
1.2 eq. Ph2PNa, Toluene, -78°C, 14 h. Reaction Conditions (Method
t b E): 1 eq. 2p, 1.2 eq. Bu2PLi, Toluene, -78°C, 14 h Isolated yield. diastereomers and displayed similar 1H, 13C, and 31P NMR resonances, differing only slightly due to electronic and steric effects caused by the imine substituent. X-ray quality crystals of 3p were produced from a solution of diethyl ether layered with pentane at -
44 25°C, and the crystal structure confirmed the connectivity of the ligand system (Figure
9). The carbon-carbon single and double bond distances and angles as well as the
carbon-phosphorus and imine bond distances and angles are similar to those observed in related compounds.140, 231 Similarly, the synthesis of 3aa was achieved by reacting 2p
with lithium di-tert-butylphosphide. Compound 3aa displayed similar alkenyl backbone
resonances in the 1H and 13C NMR spectra, however its 31P resonance was found at 13.6 ppm, a 38 ppm downfield shift from the analogous diphenyl substituted 3- iminophosphine (3p).
Several aspects of the syntheses of 3-iminophosphines 3p-aa merit further comment. The majority of these compounds are greasy solids due to extensive substitution of the imine moiety, although with sufficient effort, these complexes could be crystallized. The 31P NMR resonances appeared at -24 ppm for compounds with a
cyclopentenyl ring and -13 ppm for those with a cyclohexenyl ring. These compounds
Figure 9. ORTEP diagram (50% thermal ellipsoids) of 3p. Hydrogen atoms omitted
for clarity. Bond lengths (in Å): C1-C2 = 1.460(6), C2-C3 = 1.354(8), C3-P1 =
1.817(7). Bond angles (in deg): C1-N1-C7 = 119.5(5), C2-C1-N1 = 120.6(1), C3-C2-
C1 = 125.5(3), P1-C3-C2 = 122.7(2).
45 displayed relatively high air and moisture stability, not readily undergoing oxidation of
the phosphorus(III) to phosphorus(V) or decomposition as observed with their β- chloroimine precursors.
II-3: Experimental Methods
General Considerations. Compounds 1, 2, and 4 were synthesized under ambient atmosphere. Compounds 3 and 5-7 were synthesized using standard Schlenk and dry box techniques. n-Butyllithium (1.6 M in hexanes), tetrakis(triphenylphosphine) palladium(0), (allyl)palladium(II) chloride dimer, di-tert-butylphosphine, and diphenylchlorophosphine were purchased from Strem and used as received. CDCl3 was purchased from Cambridge Isotope Laboratories and vacuum transferred from calcium hydride. Pentane, toluene and tetrahydrofuran were purchased from Fisher and purified by passage through a column of activated 4Å molecular sieves and degassed with nitrogen prior to use. Diethyl ether was purified by passage through a column of activated alumina and degassed with nitrogen prior to use. 1,4-Dioxane was refluxed over sodium and distilled under nitrogen. N,N-Dimethylformamide and methylene chloride were purchased from Fisher and used without further purification.
Acetophenone, pinacolone, propiophenone, cyclopentanone, cyclohexanone, phosphorus pentachloride, phosphorus oxychloride, tert-butylamine, aniline, 2,6-dimethylaniline, 2,6- diethylaniline, 2,6-diisopropylaniline, 4-tert-butylaniline, and benzylamine were purchased from Acros and used without further purification. 1H and 13C NMR data were
obtained on a 600 MHz Inova NMR spectrometer at ambient temperature at 599.9 and
150.9 MHz, respectively. 31P NMR data was obtained on a 400 MHz Varian NMR
spectrometer at ambient temperature at 161.9 MHz. 1H NMR shifts are given relative to
46 13 CHCl3 (7.26 ppm) and C NMR shifts are given relative to CDCl3 (77.3 ppm).
Phosphorus NMR was externally referenced to 0.00 ppm with 5% H3PO4 in D2O. For IR, liquid samples were taken neat and solid samples prepared as Nujol mulls and taken between KBr plates on a Perkin-Elmer XTL FTIR spectrophotometer. Melting points were observed on a capillary melting point (Uni-Melt) apparatus in sealed capillary tubes and are uncorrected. Boiling points were obtained at atmospheric pressure unless otherwise noted. High resolution mass spectra were obtained using electron ionization unless otherwise noted by the Mass Spectrometry Laboratory at the University of Illinois,
Urbana, IL. Elemental analyses were determined by Columbia Analytical Services,
Tucson, AZ. X-ray structure determinations were performed at the Ohio Crystallographic
Consortium housed at The University of Toledo. Sodium diphenylphosphide,252 lithium diphenylphosphide,253 lithium di-tert-butyl phosphide,253 bis(1,5-
cyclooctadiene)nickel(0),254 tetrakis(triphenylphosphine)nickel(0),255 and
diphenyl(trimethylsilyl)phosphine250 were prepared as previously reported.
General Procedure for the Synthesis of Aliphatic α,β-Unsaturated β-
Chloroaldehydes (1a-c): Phosphorus pentachloride (36.438 g, 175.00 mmol) was added
to a stirring solution of N,N-dimethylformamide (29.246 g, 400.00 mmol) and allowed to
stir for 2 h. The mixture was cooled to 0°C and a mixture of the ketone (100.0 mmol)
and N,N-dimethylformamide (7.309 g, 100.0 mmol) was added and stirred at 36°C for an additional 12 h. The solution was poured over ice and made basic with sodium bicarbonate. After extraction with diethyl ether (3 x 100 mL), the combined organic extracts were washed with saturated sodium bicarbonate solution (2 x 100 mL) and 100 mL of saturated sodium chloride solution. The organic layer was dried over magnesium
47 sulfate for 10 min, filtered and solvent was evaporated. The ratios of E:Z were 1:10 (1a),
1:20 (1b), and 9:1 (1c).
Ph-CHO (1a): red liquid (12.499 g, 74.48%); bp 52°C (0.05 mmHg); Z-isomer: 1H
3 NMR (600 MHz) δ 10.23 (d, JHH = 7.2 Hz, 1H), 7.75-7.76 (m, 2H), 7.50-7.52 (m, 2H),
3 13 1 7.45-7.48 (m, 1H), 6.68 (d, JHH = 7.2 Hz, 1H); C{ H} NMR δ 191.7, 152.6, 135.7,
1 3 132.1, 129.1, 127.4, 124.6; E-isomer: H NMR (600 MHz) δ 9.48 (d, JHH = 7.8 Hz, 1H),
3 aromatic resonances obscured, 6.54 (d, JHH = 7.8 Hz, 1H); IR 3060 (w), 2919 (w), 2842
(w), 2749 (w), 1752 (w), 1669 (s), 1601 (s), 1570 (m), 1492 (w), 1446 (m), 1311 (w),
1228 (m), 1168 (w), 1160 (w), 1129 (s), 1077 (w), 1028 (w), 1001 (w), 926 (w), 886 (w),
837 (w), 761 (s), 734 (w), 703 (m), 685 (m), 628 (m), 583 (m); HRMScalc: 165.01072 for
+ C9H6ClO [M-H] ; HRMSmeas: 165.01078.
tBu-CHO (1b): yellow liquid (12.371 g, 84.01%); bp 94°C; 1H NMR (600 MHz) δ 10.00
3 3 13 1 (d, JHH = 5.6 Hz, 1H), 6.10 (d, JHH = 5.6 Hz, 1H), 1.20 (s, 9H); C{ H} NMR δ 192.8,
167.2, 123.2, 40.2, 28.5; IR 3080 (w), 3062 (w), 3017 (w), 2963 (s), 2917 (m), 2863 (m),
1953 (w), 1898 (w), 1808 (w), 1677 (m), 1659 (m), 1610 (s), 1487 (w), 1473 (m), 1441
(m), 1370 (s), 1320 (m), 1284 (m), 1266 (m), 1211 (s), 1175 (w), 1152 (w), 1076 (w),
1040 (m), 1022 (m), 958 (w), 931 (w), 908 (m), 890 (m), 845 (w), 818 (w), 754 (s), 696
(s), 678 (m), 642 (w), 610 (m); HRMS (electrospray ionization); HRMScalc: 145.0420
+ for C7H10ClO [M-H] ; HRMSmeas: 145.0421.
PhMe-CHO (1c): yellow liquid (12.574 g, 69.61%); bp 58°C (0.05 mmHg); E-isomer:
1H NMR (600 MHz) δ 9.48 (s, 1H), 7.42-7.50 (m, 5H), 2.09 (s, 3H); 13C{1H} NMR δ
190.7, 154.8, 136.5, 136.0, 130.6, 130.3, 128.7, 13.6; Z-isomer: 1H NMR (600 MHz) δ
10.41 (s, 1H), 7.42-7.50 (m, 5H), 1.85 (s, 3H); IR 3053 (w), 3026 (w), 2962 (w), 2918
48 (w), 2845 (m), 2746 (m), 1957 (w), 1894 (w), 1812 (w), 1726 (m), 1672 (s), 1609 (s),
1595 (m), 1586 (m), 1482 (m), 1442 (s), 1388 (m), 1374 (m), 1324 (m), 1288 (m), 1247
(s), 1220 (m), 1175 (w), 1152 (w), 1071 (m), 1017 (s), 967 (w), 926 (m), 899 (s), 863
(m), 814 (w), 764 (s), 714 (s), 696 (s), 628 (m); HRMScalc: 179.02637 for C10H8ClO [M-
+ H] ; HRMSmeas: 179.02667.
General Procedure for the Synthesis of Alicyclic α,β-Unsaturated β-
Chloroaldehydes (1d-e): The procedure used was a slight modification of that reported
by Benson and Pohland.251 Phosphorus oxychloride (1.6 equivalents) was added to a
flask containing N,N-dimethylformamide (2 equivalents) in an ice bath and stirred for 7
minutes. The ice bath was replaced with an ambient temperature water bath and stirred
for an additional 8 min. The mixture was cooled to 0oC and cyclopentanone or
cyclohexanone (1 equivalent) was added and stirred for 15 min. The ice bath was
replaced with an ambient temperature water bath and stirred for an additional 15 min.
The yellowish red solution was poured into an Erlenmeyer flask containing ice (150 g).
The solution was made basic using sodium bicarbonate. After extraction with diethyl
ether (3 x 100 mL), the combined organic extracts were washed with 100 mL of saturated
sodium bicarbonate solution, 100 mL of brine and 100 mL of water. The organic layer
was dried over magnesium sulfate for 5 min, filtered and solvent was evaporated.
Pen-CHO (1d): yellow liquid (7.397 g, 76.00%); bp 61°C (12 mm); 1H NMR (600
3 2 3 MHz) δ 10.00 (s, 1H), 2.82 (td, JHH = 7.8 Hz, JHH = 2.0 Hz, 1H), 2.81 (td, JHH = 7.8 Hz,
2 3 2 3 JHH = 2.4 Hz, 1H), 2.59 (td, JHH = 7.8 Hz, JHH = 2.4 Hz, 1H), 2.58 (td, JHH = 7.8 Hz,
2 3 13 1 JHH = 2.0 Hz, 1H), 2.01 (pent, JHH = 7.8 Hz, 2H); C{ H} NMR δ 187.8, 151.3, 137.3,
49 40.2, 28.6, 20.4; IR 2947 (s), 2719 (m), 1742 (m), 1674 (s), 1618 (s), 1430 (m), 1384 (m),
1332 (s), 1280 (w), 1244 (m), 1202 (w), 1093 (s), 943 (m).
Hex-CHO (1e): red liquid (3.466 g, 89.97%); 1H NMR (600 MHz) δ 10.19 (s, 1H), 2.56-
2.59 (m, 2H), 2.26-2.29 (m, 2H), 1.74-1.78 (m, 2H), 1.63-1.67 (m, 2H); 13C{1H} NMR δ
191.5, 151.7, 133.7, 36.1, 24.0, 23.4, 21.3; IR 3330 (w), 2932 (s), 2848 (m), 2744 (w),
2660 (w), 2356 (w), 2324 (w), 1675 (s), 1618 (s), 1450 (w), 1434 (m), 1345 (m), 1266
(w), 1214 (s), 1172 (w), 1135 (w), 1120 (w), 1093 (w), 1067 (w), 989 (s), 962 (w), 894
(w), 868 (w), 821 (m), 711 (m), 669 (w), 564 (m).
General Procedure for the Synthesis of Aliphatic α,β-Unsaturated β-Chloroimines
(2a-o): The aliphatic α,β-unsaturated β-chloroaldehyde 1a-c (5.00 mmol) was dissolved
in diethyl ether (20 mL) and cooled to 0°C. A primary amine (6.00 mmol), diluted with
10 mL of diethyl ether, was added slowly to the flask and stirred for 12 h, gradually warming to room temperature. Magnesium sulfate was added to the flask, filtered, and solvent evaporated. The ratios of E:Z were 1:10 (2a-e), 1:20 (2f-j), and 9:1 (2k-o). The
ratios of E:Z decreased to 3:1 (2m-o) due to isomerization during purification by
distillation.
Ph-tBu (2a): red liquid (0.959 g, 86.4%); bp 82°C (0.05 mmHg); 1H NMR (600 MHz) δ
3 3 8.45 (d, JHH = 8.4 Hz, 1H), 7.69-7.70 (m, 2H), 7.37-7.39 (m, 3H), 6.91 (d, JHH = 8.4 Hz,
1H), 1.27 (s, 9H); 13C{1H} NMR δ 154.8, 141.0, 137.0, 130.1, 128.8, 126.8, 125.8, 58.4,
29.9; IR 3054 (w), 2962 (s), 2921 (m), 2850 (w), 2328 (m), 1790 (w), 1765 (w), 1734
(w), 1719 (w), 1693 (w), 1673 (m), 1647 (m), 1616 (s), 1591 (m), 1555 (m), 1534 (m),
1488 (m), 1448 (m), 1360 (m), 1310 (w), 1220 (m), 1151 (m), 1071 (w), 1027 (w), 997
50 (w), 957 (w), 878 (m), 858 (m), 758 (s), 689 (m); HRMScalc: 220.0893 for C13H15NCl
+ [M-H] ; HRMSmeas: 220.0893.
Ph-Ph (2b): yellow-orange crystals (0.784 g, 64.9%); mp 65-66°C; 1H NMR (600 MHz)
3 3 δ 8.72 (d, JHH = 8.4 Hz, 1H), 7.77-7.79 (m, 2H), 7.44 (m, 3H), 7.42 (t, JHH = 7.8 Hz,
3 3 3 2H), 7.27 (t, JHH = 7.2 Hz, 1H), 7.25 (d, JHH = 7.2 Hz, 2H), 7.14 (d, JHH = 8.4 Hz, 1H);
13C{1H} NMR δ 159.7, 130.7, 129.5 (2C), 129.0 (2C), 127.1 (2C), 125.2 (2C), 121.4; IR
3054 (w), 2915 (s), 2855 (s), 2329 (m), 1956 (w), 1886 (w), 1871 (w), 1737 (w), 1672
(m), 1653 (m), 1603 (s), 1578 (s), 1558 (s), 1533 (m), 1518 (w), 1374 (w), 1350 (m),
1320 (w), 1245 (m), 1225 (s), 1191 (w), 1166 (s), 1101 (w), 1076 (m), 1022 (m), 997
(m), 967 (m), 898 (m), 868 (s), 763 (s), 684 (s); HRMScalc: 240.0580 for C15H11NCl [M-
+ H] ; HRMSmeas: 240.0581.
1 Ph-2,6-Me2Ph (2c): red-orange crystals (0.966 g, 71.7%); mp 55-56°C; H NMR (600
3 3 MHz) δ 8.45 (d, JHH = 8.4 Hz, 1H), 7.79-7.81 (m, 2H), 7.44-7.46 (m, 3H), 7.19 (d, JHH =
3 3 8.4 Hz, 1H), 7.09 (d, JHH = 7.2 Hz, 2H), 6.98 (t, JHH = 7.2 Hz, 1H), 2.18 (s, 6H);
13C{1H} NMR δ 162.1, 151.6, 144.1, 136.7, 130.7, 128.9, 128.4, 127.3, 127.1, 125.1,
124.4, 18.7; IR 3176 (w), 3057 (w), 2920 (s), 2847 (s), 2728 (w), 2675 (w), 1677 (w),
1613 (m), 1590 (m), 1527 (w), 1461 (s), 1374 (m), 1310 (w), 1223 (m), 1187 (w), 1155
(m), 1086 (w), 1031 (w), 999 (w), 979 (w), 970 (w), 892 (w), 851 (w), 832 (w), 760 (m),
+ 709 (m), 681 (m), 650 (w); HRMScalc: 268.0893 for C17H15NCl [M-H] ; HRMSmeas:
268.0894.
1 Ph-2,6-Et2Ph (2d): orange crystals (1.052 g, 70.7%); mp 80-81°C; H NMR (600 MHz)
3 3 δ 8.45 (d, JHH = 8.4 Hz, 1H), 7.81-7.83 (m, 2H), 7.46-7.48 (m, 3H), 7.23 (d, JHH = 8.4
3 3 Hz, 1H), 7.12-7.13 (m, 2H), 7.07-7.10 (m, 1H), 2.53 (q, JHH = 7.8 Hz, 4H) 1.18 (t, JHH =
51 7.8 Hz, 6H); 13C{1H} NMR δ 162.0, 150.8, 144.3, 136.7, 133.4, 130.9, 129.0, 127.2,
126.6, 126.5, 124.9, 25.0, 15.2; IR 3054 (w), 2915 (s), 2845 (s), 2329 (m), 1772 (w),
1717 (w), 1697 (w), 1673 (w), 1653 (w), 1603 (s), 1578 (m), 1558 (m), 1543 (w), 1519
(w), 1489 (m), 1374 (m), 1240 (m), 1220 (m), 1156 (s), 1101 (m), 1076 (w), 1022 (w),
992 (w), 893 (m), 848 (m), 808 (m), 763 (s), 708 (m), 684 (m), 669 (m); HRMScalc:
297.1284 for C19H20NCl; HRMSmeas: 297.1281.
i Ph-2,6- Pr2Ph (2e): yellow powder which was recrystallized from pentane to yield
1 3 yellow crystals (1.276 g, 78.3%); mp 117-118°C; H NMR (600 MHz) δ 8.42 (d, JHH =
3 8.4 Hz, 1H), 7.81-7.83 (m, 2H), 7.46-7.47 (m, 3H), 7.23 (d, JHH = 8.4 Hz, 1H), 7.21-7.22
3 3 (m, 2H), 7.16-7.19 (m, 1H), 2.99 (sept, JHH = 6.6 Hz, 2H), 1.21 (d, JHH = 6.6 Hz. 12H);
13C{1H} NMR δ 161.7, 149.5, 144.2, 137.9, 136.6, 130.7, 128.9, 127.2, 127.1, 124.8,
123.4, 28.1, 23.9; IR 3064 (w), 3014 (w), 2964 (s), 2855 (s), 2358 (m), 2328 (m), 1772
(w), 1737 (w), 1697 (m), 1653 (w), 1608 (s), 1583 (m), 1558 (m), 1494 (m), 1379 (m),
1360 (m), 1320 (w), 1250 (m), 1220 (m), 1191 (m), 1156 (m), 1106 (w), 1076 (w), 898
(w), 873 (m), 828 (w), 763 (s), 709 (m), 689 (m), 664 (m); HRMScalc: 325.1597 for
C21H24NCl; HRMSmeas: 325.1600.
tBu-tBu (2f): yellow liquid (0.825 g, 82.5%); bp 36°C (0.05 mmHg); 1H NMR (600
3 3 MHz) δ 8.17 (d, JHH = 6.0 Hz, 1H); 6.20 (d, JHH = 6.0 Hz, 1H), 1.194 (s, 9H), 1.188 (s,
9H); 13C{1H} NMR δ 155.3, 155.0, 122.7, 57.9, 39.7, 29.9, 28.8; IR 2968 (s), 2926 (m),
2874 (m), 1706 (w), 1659 (w), 1633 (s), 1576 (w), 1477 (m), 1462 (m), 1389 (w), 1358
(m), 1296 (w), 1254 (m), 1233 (m), 1213 (m), 1150 (w), 1103 (w), 1082 (w), 1026 (w),
974 (m), 854 (m), 797 (m), 766 (w), 652 (m); HRMScalc: 201.1284 for C11H20NCl;
HRMSmeas: 201.1282.
52 t 1 3 Bu-Ph (2g): yellow solid; H NMR (600 MHz) δ 8.54 (d, JHH = 9.0 Hz, 1H), 7.38 (t,
3 3 3 3 JHH = 7.8 Hz, 2H), 7.22 (t, JHH = 7.8 Hz, 1H), 7.19 (d, JHH = 7.8 Hz, 2H), 6.68 (d, JHH
= 9.0 Hz, 1H), 1.28 (s, 9H).
t 1 Bu-2,6-Me2Ph (2h): yellow crystals (1.097 g, 87.9%); mp 46-47°C; H NMR (600
3 3 3 MHz) δ 8.28 (d, JHH = 8.4 Hz, 1H), 7.05 (d, JHH = 7.8 Hz, 2H), 6.94 (t, JHH = 7.8 Hz,
3 13 1 1H), 6.62 (d, JHH = 8.4 Hz, 1H), 2.14 (s, 6H), 1.31 (s, 9H); C{ H} NMR δ 162.3,
158.0, 151.0, 127.9, 126.8, 123.7, 121.8, 39.6, 28.4, 18.2; IR 3061 (w), 3009 (m), 2926
(s), 2864 (s), 1627 (m), 1586 (w), 1462 (s), 1379 (m), 1358 (m), 1254 (m), 1192 (m),
1150 (m), 1088 (w), 1026 (w), 997 (w), 969 (m), 855 (m), 829 (w), 798 (w), 766 (m), 709
+ (m), 637 (m), 606 (w); HRMScalc: 248.1206 for C15H19NCl [M-H] ; HRMSmeas:
248.1206.
t 1 Bu-2,6-Et2Ph (2i): yellow liquid (1.250 g, 89.9%); bp 88°C (0.05 mmHg); H NMR
3 3 3 (600 MHz) δ 8.25 (d, JHH = 7.8 Hz, 1H), 7.08 (d, JHH = 7.2 Hz, 2H), 7.03 (t, JHH = 7.2
3 3 Hz, 1H), 6.57 (d, JHH = 7.8 Hz, 1H), 2.47 (q, JHH = 7.8 Hz, 4H), 1.31 (s, 9H), 1.15 (t,
3 13 1 JHH = 7.8 Hz, 6H); C{ H} NMR δ 162.4, 158.3, 133.4, 126.5, 126.3, 124.4, 122.2,
40.1, 28.9, 24.8, 15.1; IR 3060 (m), 2959 (s), 2932 (s), 2867 (s), 2355 (w), 1916 (w),
1852 (w), 1793 (w), 1678 (w), 1628 (s), 1586 (m), 1449 (s), 1394 (w), 1357 (m), 1289
(w), 1248 (m), 1206 (m), 1183 (m), 1151 (m), 1100 (m), 1077 (w), 1059 (w), 1026 (w),
962 (m), 852 (m), 838 (m), 802 (m), 756 (s), 706 (m), 637 (m), 600 (s); HRMScalc:
277.1597 for C17H24NCl; HRMSmeas: 277.1598.
t i 1 Bu-2,6- Pr2Ph (2j): yellow crystals (1.327 g, 86.7%); mp 66-68°C; H NMR (600 MHz)
3 3 3 δ 8.22 (d, JHH = 8.4 Hz, 1H), 7.15 (d, JHH = 7.8 Hz, 2H), 7.11 (t, JHH = 7.8 Hz, 1H),
3 3 3 6.57 (d, JHH = 8.4 Hz, 1H), 2.92 (sept, JHH = 6.6 Hz, 2H), 1.31 (s, 9H), 1.17 (d, JHH =
53 6.6 Hz, 12H); 13C{1H} NMR δ 162.4, 158.3, 138.0, 124.6, 123.3, 122.1, 118.8, 40.1,
28.9, 28.0, 23.9; IR 3061 (w), 2963 (s), 2919 (s), 2857 (s), 2723 (w), 1921 (w), 1859 (w),
1792 (w), 1721 (w), 1668 (w), 1624 (s), 1606 (m), 1588 (m), 1464 (s), 1437 (m), 1379
(m), 1361 (m), 1321 (m), 1250 (m), 1206 (w), 1179 (w), 1152 (m), 1108 (w), 1094 (w),
1059 (w), 1041 (w), 1023 (w), 961 (m), 930 (w), 903 (w), 881 (w), 859 (m), 832 (w), 801
(m), 757 (s), 721 (w), 698 (w), 646 (m), 601 (m); HRMScalc: 305.1910 for C19H28NCl;
HRMSmeas: 305.1910.
PhMe-tBu (2k): orange liquid (1.103 g, 93.6%); bp 30°C (0.10 mmHg); 1H NMR (600
MHz) δ 7.88 (s, 1H), 7.34-7.37 (m, 5H), 2.22 (s, 3H), 1.10 (s, 9H); 13C{1H} NMR δ
155.2, 139.8, 137.9, 134.7, 130.1, 129.2, 128.4, 57.6, 29.9, 15.9; IR 3221 (w), 3084 (w),
3058 (w), 3021 (w), 2966 (s), 2930 (m), 2866 (m), 2737 (w), 1952 (w), 1897 (w), 1810
(w), 1718 (w), 1677 (m), 1659 (m), 1617 (s), 1594 (m), 1575 (w), 1485 (w), 1471 (m),
1443 (m), 1375 (m), 1355 (m), 1324 (m), 1283 (m), 1260 (m), 1210 (s), 1173 (w), 1154
(w), 1099 (w), 1076 (w), 1039 (m), 1021 (m), 957 (w), 929 (m), 911 (m), 897 (m), 847
(w), 814 (w), 778 (w), 760 (s), 700 (s), 672 (m), 636 (m), 613 (m); HRMScalc: 234.1050
+ for C14H17NCl [M-H] ; HRMSmeas: 234.1052.
PhMe-Ph (2l): yellow crystals (1.012 g, 79.2%); mp 72-74°C; 1H NMR (600 MHz) δ
3 3 8.09 (s, 1H), 7.40-7.44 (m, 5H), 7.31 (t, JHH = 7.2 Hz, 2H), 7.17 (t, JHH = 7.2 Hz, 1H),
3 13 1 7.00 (d, JHH = 7.2 Hz, 2H), 2.38 (s, 3H); C{ H} NMR δ 159.7, 152.3, 143.9, 137.6,
134.8, 130.1, 129.7, 129.3, 128.7, 126.1, 121.1, 15.7; IR 3051 (w), 2962 (s), 2927 (s),
2856 (s), 2722 (w), 2357 (w), 1605 (w), 1579 (m), 1481 (m), 1459 (m), 1370 (m), 1312
(w), 1286 (w), 1263 (w), 1223 (w), 1201 (m), 1161 (w), 1077 (w), 1019 (w), 970 (w),
54 930 (w), 899 (m), 846 (w), 757 (s), 721 (w), 686 (m), 628 (m); HRMScalc: 254.0736 for
+ C16H13NCl [M-H] ; HRMSmeas: 254.0738.
PhMe-2,6-Me2Ph (2m): red liquid (1.150 g, 81.0%); bp >170°C (0.05 mmHg); E-
1 3 isomer: H NMR (600 MHz) δ 7.77 (s, 1H), 7.36-7.37 (m, 5H), 7.00 (d, JHH = 7.8 Hz,
3 13 1 2H), 6.90 (t, JHH = 7.8 Hz, 1H), 2.42 (s, 3H), 2.08 (s, 6H); C{ H} NMR δ 161.7, 151.2,
143.9, 137.5, 134.6, 129.9, 129.6, 128.6, 128.2, 127.0, 123.9, 18.6, 15.4; Z-isomer: 1H
3 3 NMR (600 MHz) δ 8.69 (s, 1H), 7.50 (d, JHH = 7.2 Hz, 2H), 7.46 (t, JHH = 7.2 Hz, 2H),
3 3 3 7.42 (t, JHH = 7.2 Hz, 1H), 7.10 (d, JHH = 7.8 Hz, 2H), 6.98 (t, JHH = 7.8 Hz, 1H), 2.19
(s, 3H), 2.16 (s, 6H); 13C{1H} NMR δ 163.1, 151.5, 138.7, 132.0, 130.3, 129.4, 129.2,
128.6, 128.3, 127.1, 124.1, 18.9, 16.2; IR 3198 (w), 3060 (m), 3015 (m), 2951 (m), 2914
(m), 2850 (m), 2722 (w), 2034 (w), 1953 (w), 1912 (w), 1848 (w), 1806 (w), 1770 (w),
1692 (w), 1614 (s), 1587 (s), 1536 (w), 1468 (s), 1440 (s), 1376 (m), 1358 (m), 1316 (w),
1284 (m), 1266 (m), 1220 (m), 1193 (s), 1161 (w), 1091 (m), 1074 (w), 1028 (s), 987
(w), 964 (w), 895 (s), 844 (m), 762 (s), 721 (m), 698 (s), 661 (m), 629 (m), 601 (m);
+ HRMScalc: 282.1050 for C18H17NCl [M-H] ; HRMSmeas: 282.1048.
PhMe-2,6-Et2Ph (2n): red liquid (1.313 g, 84.2%); bp >170°C (0.05 mmHg); E-isomer:
1 3 H NMR (600 MHz) δ 7.82 (s, 1H), 7.36-7.40 (m, 5H), 7.06 (d, JHH = 7.2 Hz, 2H), 7.00
3 3 3 (t, JHH = 7.2 Hz, 1H), 2.44 (q, JHH = 7.2 Hz, 4H), 2.44 (s, 3H), 1.12 (t, JHH = 7.2 Hz,
6H); 13C{1H} NMR δ 161.1, 150.4, 143.8, 137.5, 134.6, 132.9, 129.8, 129.6, 128.7,
126.4, 124.1, 24.9, 15.4, 14.9; Z-isomer: 1H NMR (600 MHz) δ 8.65 (s, 1H), 7.50 (d,
3 3 3 3 JHH = 7.2 Hz, 2H), 7.45 (pseudo t, JHH = 7.2 Hz, JHH = 7.8 Hz, 2H), 7.41 (t, JHH = 7.8
3 3 3 Hz, 1H) 7.11 (d, JHH = 7.8 Hz, 2H), 7.05 (t, JHH = 7.8 Hz, 1H), 2.51 (q, JHH = 7.2 Hz,
3 13 1 4H), 2.14 (s, 3H), 1.19 (t, JHH = 7.2 Hz, 6H); C{ H} NMR δ 162.5, 150.8, 139.4,
55 138.6, 133.1, 131.9, 129.4, 129.2, 128.6, 126.5, 124.3, 25.0, 16.2, 14.9; IR 3062 (m),
3018 (m), 2953 (s), 2924 (s), 2864 (s), 1700 (w), 1616 (s), 1592 (s), 1488 (m), 1448 (s),
1374 (m), 1320 (w), 1285 (m), 1260 (m), 1226 (w), 1186 (s), 1166 (w), 1102 (m), 1077
(w), 1062 (w), 1038 (m), 1023 (m), 968 (w), 929 (w), 894 (m), 870 (w), 850 (m), 800
+ (w), 761 (s), 721 (m), 693 (s), 666 (m); HRMScalc: 310.1362 for C20H21NCl [M-H] ;
HRMSmeas: 310.1363.
i PhMe-2,6- Pr2Ph (2o): red liquid (1.314 g, 77.3%); bp >170°C (0.05 mmHg); E-isomer:
1 3 H NMR (600 MHz) δ 7.75 (s, 1H), 7.33-7.35 (m, 5H), 7.08 (d, JHH = 7.2 Hz, 2H), 7.04
3 3 3 (t, JHH = 7.2 Hz, 1H), 2.85 (sept, JHH = 7.2 Hz, 2H), 2.41 (s, 3H), 1.11 (d, JHH = 7.2 Hz,
12H); 13C{1H} NMR δ 161.3, 150.4, 149.3, 143.9, 137.5, 134.6, 129.8, 129.6, 128.7,
124.3, 123.2, 28.1, 23.7, 15.4; Z-isomer: 1H NMR (600 MHz) δ 8.60 (s, 1H), 7.50 (d,
3 3 3 3 JHH = 7.2 Hz, 2H), 7.45 (pseudo t, JHH = 7.2 Hz, JHH = 7.8 Hz, 2H), 7.40 (t, JHH = 7.8
3 3 3 Hz, 1H), 7.17 (d, JHH = 7.8 Hz, 2H), 7.11 (t, JHH = 7.8 Hz, 1H), 2.94 (sept, JHH = 6.6
3 13 1 Hz, 2H), 2.14 (s, 3H), 1.21 (d, JHH = 6.6 Hz, 12H); C{ H} NMR δ 162.6, 150.8, 149.6,
138.6, 137.6, 131.9, 129.4, 129.3, 128.6, 124.5, 123.3, 28.2, 23.9, 16.2; IR 3058 (m),
3025 (m), 2958 (s), 2916 (s), 2886 (s), 2724 (w), 1948 (w), 1914 (w), 1806 (w), 1693
(w), 1614 (s), 1591 (s), 1514 (w), 1487 (m), 1460 (s), 1442 (s), 1379 (m), 1361 (m), 1320
(m), 1284 (m), 1266 (s), 1237 (m), 1184 (s), 1162 (w), 1098 (m), 1071 (m), 1022 (s), 967
(w), 927 (m), 900 (s), 845 (m), 796 (m), 759 (s), 714 (s), 701 (s), 674 (w), 624 (m);
+ HRMScalc: 338.1676 for C22H25NCl [M-H] ; HRMSmeas: 338.1676.
General Procedure for the synthesis of Alicyclic α,β-Unsaturated β-Chloroimines
(2p-z): 1d/e (1 equivalent) was dissolved in diethyl ether (20 mL) and cooled to 0 °C for
5 min. Activated 4Å molecular sieves were added to the solution. A primary amine (1.1
56 equivalents) diluted with diethyl ether (10 mL) was added and the mixture was stirred for
14 h, gradually warming to room temperature. The solution was passed through a pad of
Celite® and solvent evaporated. Isolated products showed evidence of decomposition at room temperature after 8 h and at -25 °C after 96 h.
Pen-tBu (2p): orange-red liquid (10.247 g, 97.48%); bp 102-105 °C; 1H NMR (600
3 2 3 MHz) δ 8.24 (s, 1H), 2.70 (td, JHH = 7.8 Hz, JHH = 2.4 Hz, 1H), 2.70 (td, JHH = 7.8 Hz,
2 3 2 3 JHH = 2.0 Hz, 1H), 2.64 (td, JHH = 7.8 Hz, JHH = 2.4 Hz, 1H), 2.63 (td, JHH = 7.8 Hz,
2 3 13 1 JHH = 2.0 Hz, 1H), 1.96 (pent, JHH = 7.8 Hz, 2H), 1.22 (s, 9H); C{ H} NMR δ 150.3,
137.8, 135.9, 57.6, 39.3, 30.5, 29.7, 20.6; IR 2968 (s), 1628 (s), 1472 (w), 1363 (m), 1254
(w), 1213 (m), 1099 (m), 1026 (w), 948 (m).
1 Pen-2,6-Me2Ph (2q): orange-red liquid (3.563 g, 95.77%); H NMR (600 MHz) δ 8.23
3 3 3 (s, 1H), 7.05 (d, JHH = 7.8 Hz, 2H), 6.94 (t, JHH = 7.8 Hz, 1H), 2.86 (td, JHH = 7.8 Hz,
2 3 2 3 JHH = 2.1 Hz, 1H), 2.85 (td, JHH = 7.8 Hz, JHH = 2.4 Hz, 1H), 2.82 (td, JHH = 7.8 Hz,
2 3 2 JHH = 2.1 Hz, 1H), 2.81 (td, JHH = 7.8 Hz, JHH = 2.4 Hz, 1H), 2.12 (s, 6H), 1.96 (pent,
3 13 1 JHH = 7.8 Hz, 2H); C{ H} NMR δ 157.6, 151.4, 141.7, 135.8, 128.2, 127.9, 124.0,
39.9, 30.5, 20.9, 18.6; IR 3062 (w), 3020 (w), 2957 (s), 2915 (s), 2852 (m), 2727 (w),
2360 (w), 2035 (w), 1918 (w), 1839 (w), 1724 (w), 1656 (m), 1625 (s), 1609 (s), 1593
(s), 1467 (s), 1441 (m), 1378 (m), 1347 (m), 1274 (m), 1247 (m), 1190 (s), 1158 (w),
1090 (m), 1033 (w), 985 (w), 938 (m), 912 (w), 844 (m), 760 (s), 723 (m), 671 (w).
1 Pen-2,6-Et2Ph (2r): red liquid (8.090 g, 94.44%); H NMR (600 MHz) δ 8.22 (s, 1H),
3 3 3 7.08 (d, JHH = 7.8 Hz, 2H), 7.03 (t, JHH = 7.8 Hz, 1H), 2.81-2.87 (m, 4H), 2.47 (q, JHH =
3 3 3 7.8 Hz, 4H), 2.11 (pseudo pent, JHH = 7.8 Hz, JHH = 7.2 Hz, 2H), 1.15 (t, JHH = 7.8 Hz,
6H); 13C{1H} NMR δ 157.1, 150.7, 141.6, 135.8, 132.8, 126.1, 123.9, 39.6, 30.2, 24.6,
57 20.6, 14.7; IR 3195 (w), 3050 (m), 2956 (s), 2925 (s), 2862 (s), 2717 (w), 2634 (w), 2032
(w), 1912 (w), 1850 (w), 1793 (w), 1726 (w), 1700 (w), 1627 (w), 1591 (m), 1451 (s),
1373 (m), 1348 (m), 1285 (w), 1248 (m), 1186 (m), 1160 (w), 1093 (m), 1056 (w), 1036
(w), 1004 (w), 942 (m), 910 (w), 871 (w), 848 (m), 805 (m), 766 (m), 735 (m), 672 (w).
i 1 Pen-2,6- Pr2Ph (2s): orange liquid (10.683 g, 97.26%); H NMR (600 MHz) δ 8.18 (s,
3 3 3 1H), 7.14 (d, JHH = 6.6 Hz, 2H), 7.08 (t, JHH = 6.6 Hz, 1H), 2.89 (sept, JHH = 7.2 Hz,
3 3 2H), 2.81-2.86 (m, 4H), 2.11 (pseudo pent, JHH = 7.8 Hz, JHH = 7.2 Hz, 2H), 1.15 (d,
3 13 1 JHH = 7.2 Hz, 12H); C{ H} NMR δ 157.2, 149.5, 141.7, 135.8, 125.2, 124.1, 122.9,
39.6, 30.2, 27.8, 23.5, 20.6; IR 3064 (w), 3020 (w), 2959 (s), 2917 (m), 2855 (m), 1914
(w), 1851 (w), 1725 (w), 1625 (s), 1604 (m), 1584 (m), 1458 (m), 1432 (m), 1379 (w),
1354 (m), 1327 (w), 1253 (w), 1181 (m), 1154 (w), 1087 (m), 1060 (w), 1039 (w), 981
(w), 944 (w), 882 (w), 850 (w), 798 (w), 766 (w), 730 (m).
Pen-4-tBu-Ph (2t): yellow solid (1.949 g, 97.45%); 1H NMR (600 MHz) δ 8.46 (s, 1H),
3 3 7.38 (d, JHH = 7.2 Hz, 2H), 7.11 (d, JHH = 7.2 Hz, 2H), 2.78-2.79 (m, 4H) 2.11 (pseudo
3 3 13 1 pent, JHH = 7.8 Hz, JHH = 7.2 Hz, 2H), 1.32 (s, 9H); C{ H} NMR δ 154.6, 149.4,
141.9, 136.4, 126.4, 126.2, 120.9, 39.8, 31.6, 31.4, 30.6, 21.0; IR 3156 (w), 3030 (w),
2957 (s), 2905 (s), 2859 (s), 1924 (w), 1897 (w), 1678 (w), 1641 (m), 1625 (s), 1594 (s),
1552 (s), 1521 (m), 1500 (s), 1452 (s), 1390 (m), 1353 (s), 1316 (m), 1301 (m), 1269 (m),
1217 (m), 1196 (m), 1180 (w), 1112 (w), 1097 (w), 1018 (w), 981 (w), 945 (w), 840 (m),
788 (s), 762 (s), 704 (w), 673 (w), 573 (w).
1 Pen-CH2Ph (2u): yellow liquid (1.877 g, 93.85%); H NMR (600 MHz) δ 8.30 (s, 1H),
3 7.33 (t, JHH = 7.6 Hz, 2H), 7.27-7.30 (m, 3H), 4.74 (s, 2H), 2.68-2.76 (m, 4H) 2.11
3 3 13 1 (pseudo pent, JHH = 7.8 Hz, JHH = 7.2 Hz, 2H); C{ H} NMR δ 151.3, 139.5, 135.7,
58 128.7, 128.5, 128.2, 127.2, 65.8, 39.6, 30.8, 21.0; IR 3082 (w), 3064 (w), 3026 (m), 2951
(m), 2914 (m), 2848 (m), 2726 (w), 1946 (w), 1867 (w), 1806 (w), 1698 (w), 1670 (m),
1632 (m), 1609 (m), 1581 (w), 1491 (m), 1451 (m), 1437 (m), 1366 (m), 1336 (w), 1310
(w), 1293 (w), 1262 (w), 1248 (w), 1200 (w), 1158 (w), 1101 (s), 1026 (m), 1025 (s),
1002 (m), 960 (m), 932 (m), 906 (w), 822 (w), 734 (s), 695 (s), 610 (m).
Hex-tBu (2v): yellow-orange liquid (1.626 g, 81.30%); 1H NMR (600 MHz) δ 8.46 (s,
1H), 2.46-2.50 (m, 2H), 2.38-2.42 (m, 2H), 1.71-1.77 (m, 2H), 1.62-1.68 (m, 2H), 1.21
(s, 9H); 13C{1H} NMR δ 154.2, 138.7, 131.7, 57.4, 35.2, 29.8, 26.0, 23.7, 21.8; IR 2964
(s), 2932 (s), 2859 (s), 2356 (w), 2324 (w), 1717 (w), 1691 (w), 1623 (m), 1560 (w),
1455 (w), 1434 (w), 1366 (m), 1266 (w), 1240 (w), 1209 (m), 1172 (w), 1135 (w), 1115
(w), 1099 (w), 1072 (w), 1025 (w), 989 (m), 957 (w), 905 (w), 868 (w), 826 (w), 779 (w),
695 (w).
1 Hex-2,6-Me2Ph (2w): red liquid (1.838 g, 91.90%); H NMR (600 MHz) δ 8.44 (s, 1H),
3 3 7.04 (d, JHH = 7.2 Hz, 2H), 6.92 (t, JHH = 7.2 Hz, 1H), 2.59-2.62 (m, 2H), 2.55-2.58 (m,
2H), 2.10 (s, 6H), 1.81-1.85 (m, 2H), 1.74-1.78 (m, 2H); 13C{1H} NMR δ 161.8, 151.7,
142.6, 131.8, 128.2, 127.1, 123.8, 35.6, 25.8, 23.8, 21.8, 18.6; IR 3288 (w), 3007 (w),
2932 (s), 2858 (m), 2728 (w), 2356 (w), 2328 (w), 1918 (w), 1848 (w), 1690 (m), 1616
(s), 1588 (m), 1527 (w), 1472 (s), 1439 (m), 1379 (w), 1355 (w), 1318 (w), 1272 (w),
1230 (m), 1193 (m), 1165 (w), 1128 (w), 1086 (m), 1035 (w), 988 (m), 914 (w), 895 (w),
877 (w), 844 (w), 825 (m), 765 (s), 732 (w), 719 (m), 663 (m).
1 Hex-2,6-Et2Ph (2x): red liquid (1.913 g, 95.65%); H NMR (600 MHz) δ 8.43 (s, 1H),
3 3 7.07 (d, JHH = 7.8 Hz, 2H), 7.01 (t, JHH = 7.8 Hz, 1H), 2.60-2.62 (m, 2H), 2.56-2.59 (m,
3 3 2H), 2.44 (q, JHH = 7.8 Hz, 4H), 1.81-1.85 (m, 2H), 1.74-1.78 (m, 2H), 1.13 (t, JHH = 7.8
59 Hz, 6H); 13C{1H} NMR δ 161.3, 151.0, 142.4, 133.2, 131.8, 126.4, 124.1, 35.6, 25.8,
24.9, 23.8, 21.9, 15.0; IR 3057 (w), 2953 (s), 2923 (s), 2860 (s), 2040 (w), 1911 (w),
1849 (w), 1792 (w), 1740 (w), 1693 (m), 1621 (m), 1589 (m), 1527 (w), 1449 (s), 1372
(m), 1351 (m), 1320 (w), 1268 (w), 1226 (m), 1190 (m), 1166 (m), 1117 (m), 1076 (w),
1060 (w), 1040 (w), 988 (m), 925 (w), 868 (w), 843 (w), 823 (w), 801 (m), 760 (m), 744
(m), 718 (m), 661 (w).
i 1 Hex-2,6- Pr2Ph (2y): red liquid (1.960 g, 98.0%); H NMR (600 MHz) δ 8.40 (s, 1H),
3 3 3 7.13 (d, JHH = 7.2 Hz, 2H), 7.08 (t, JHH = 7.2 Hz, 1H), 2.88 (sept, JHH = 7.2 Hz, 2H),
2.60-2.62 (m, 2H), 2.56-2.58 (m, 2H), 1.82-1.86 (m, 2H), 1.75-1.79 (m, 2H), 1.16 (d,
3 13 1 JHH = 7.2 Hz, 12H); C{ H} NMR δ 161.4, 149.8, 142.5, 137.7, 131.8, 124.3, 123.2,
35.6, 28.1, 25.9, 23.8, 22.7, 21.9; IR 3058 (w), 2963 (s), 2867 (s), 2018 (w), 1954 (w),
1912 (w), 1853 (w), 1795 (w), 1694 (w), 1614 (s), 1587 (m), 1460 (m), 1438 (m), 1380
(m), 1353 (m), 1321 (w), 1263 (m), 1226 (m), 1183 (m), 1114 (m), 1061 (w), 1045 (w),
992 (m), 960 (w), 928 (w), 880 (w), 842 (w), 826 (w), 795 (m), 763 (m), 741 (m), 720
(m), 662 (w).
1 Hex-CH2Ph (2z): red liquid (1.846 g, 92.30%) H NMR (600 MHz) δ 8.62 (s, 1H), 7.32-
7.35 (m, 3H), 7.27-7.28 (m, 2H), 4.73 (s, 2H), 2.50-2.52 (m, 2H), 2.45-2.47 (m, 2H),
1.74-1.78 (m, 2H), 1.64-1.67 (m, 2H); 13C{1H} NMR δ 161.2, 139.7, 131.6, 128.7, 128.3,
128.1, 127.2, 65.4, 35.5, 26.3, 23.9, 21.9; IR 3070 (w), 3058 (m), 3018 (m), 2973 (m),
2921 (s), 2880 (s), 2867 (s), 2665 (w), 2356 (w), 2324 (w), 1949 (w), 1869 (w), 1806 (w),
1736 (w), 1688 (w), 1625 (s), 1578 (w), 1492 (m), 1449 (s), 1433 (m), 1369 (s), 1343
(m), 1300 (w), 1268 (w), 1231 (m), 1199 (w), 1172 (w), 1151 (w), 1146 (m), 1071 (m),
60 1029 (m), 992 (s), 970 (w), 901 (w), 832 (m), 812 (m), 752 (s), 731 (s), 699 (s), 640 (w),
614 (m).
General Synthesis of α,β-Unsaturated-3-Iminophosphines (3a-aa): Method A: Three
Schlenk tubes were charged with bis(1,5-cyclooctadiene)nickel(0) (0.075 mmol), the
corresponding α,β-unsaturated β-chloroimine (1.50 mmol), and
diphenyl(trimethylsilyl)phosphine (1.80 mmol). 5 mL of toluene was added to each
Schlenk tube. The contents of the Schlenk tubes were combined and heated to reflux for
14 h. The solution was cooled to room temperature and passed through a pad of Celite®
545. Solvent was removed to yield the crude product primarily, with only minimal
catalyst contamination. The solid was recrystallized from either pentane or diethyl ether
at -25°C. Method B: Two Schlenk tubes were charged with the corresponding α,β-
unsaturated β-chloroimine (1.50 mmol) and lithium diphenylphosphide (1.80 mmol). 30
mL of toluene was added to each Schlenk tube and cooled to -78°C for 10 min. The α,β-
unsaturated β-chloroimine was added to the lithium diphenylphosphide and stirred for an
additional 14 h, slowly warming to ambient temperature. Solvent was evaporated and the
crude product was triturated with pentane (10 mL). The product was extracted from the
leftover lithium diphenylphosphide with pentane (3 x 25 mL). Method C: Freshly prepared 2 (1 equivalent) was diluted with 10 mL of toluene and cooled to 0oC. The solution was added to a slurry of lithium diphenylphosphide (1.2 equivalents) in 10 mL of toluene at 0oC. The reaction was stirred at 0 °C for 1 h and at room temperature for 2 h followed by a workup identical to that in Method B. Method D: Freshly prepared 2 (1 equivalent) diluted with 10 mL of tetrahydrofuran was cooled in an ice bath and added to a previously prepared slurry of sodium diphenylphosphide (1.3 equivalents), 20 mL of
61 tetrahydrofuran, and 90 mL of 1,4-dioxane. The reaction was stirred at room temperature
for 3 h followed by a workup identical to that in Method B. Method E: Freshly
prepared 2 (1 equivalent) was diluted with 10 mL of toluene and cooled to 0oC. The solution was added to a slurry of lithium di-tert-butylphosphide (1.2 equivalents) in 10 mL of toluene at 0oC. The reaction was stirred at 0 °C for 1 h and at room temperature for
2 h followed by a workup identical to that in Method B. 3a-f, 3h, and 3k-z were
recrystallized from either pentane or diethyl ether. The ratios of E:Z were 20:1 (3a-e),
1:25 (3f-j) and 10:1 (3k-o).
Ph2-Ph-tBu (3a): tan solid (0.416 g, 74.6%); mp 128-130°C; 1H NMR (600 MHz) δ 7.88
3 3 4 (d, JHH = 8.4 Hz, 1H), 7.40-7.43 (m, 4H), 7.37 (dd, JHH = 7.2 Hz, JHH = 0.6 Hz, 2H),
3 3 3 7.30-7.32 (m, 6H), 7.27 (t, JHH = 7.2 Hz, 2H), 7.21 (t, JHH = 7.2 Hz, 1H), 6.20 (dd, JHH
3 13 1 1 = 8.4 Hz, JPH = 4.8 Hz, 1H), 1.09 (s, 9H); C{ H} NMR δ 156.5, 153.3 (d, JPC = 21.0
1 2 2 Hz), 139.2 (d, JPC = 21.0 Hz), 135.6 (d, JPC = 8.0 Hz), 134.9 (d, JPC = 20.2 Hz), 130.6
2 3 3 (d, JPC = 13.2 Hz), 129.7 (d, JPC = 8.4 Hz), 129.6, 128.9 (d, JPC = 7.8 Hz), 128.3, 128.1,
57.7, 29.9; 31P{1H} NMR δ 4.7; IR 3051 (w), 2962 (s), 2918 (s), 2847 (s), 2722 (w), 2689
(w), 1956 (w), 1885 (w), 1810 (w), 1663 (w), 1614 (m), 1579 (w), 1459 (s), 1436 (m),
1374 (m), 1307 (w), 1259 (w), 1210 (m), 1183 (w), 1156 (w), 1133 (m), 1092 (m), 1023
(m), 1000 (w), 936 (w), 918 (w), 890 (w), 803 (w), 785 (w), 767 (m), 739 (m), 693 (s);
HRMScalc: 371.1803 for C25H26NP; HRMSmeas: 371.1802.
Ph2-Ph-Ph (3b): red solid (0.419 g, 71.4%); mp 128-131°C; 1H NMR (600 MHz) δ 8.08
3 (d, JHH = 9.0 Hz, 1H), 7.44-7.47 (m, 6H), 7.35-7.36 (m, 6H), 7.23-7.30 (m, 5H), 7.14-
3 3 13 1 7.16 (m, 1H), 6.98-6.99 (m, 2H), 6.34 (dd, JHH = 9.0 Hz, JPH = 4.2 Hz, 1H); C{ H}
1 1 NMR δ 159.9, 157.5, 152.1, 138.8 (d, JPC = 20.4 Hz), 134.983 (d, JPC = 20.4 Hz),
62 2 2 134.983 (d, JPC = 8.1 Hz), 133.8 (d, JPC = 9.4 Hz), 129.8, 129.7, 129.3, 129.0, 128.54,
128.52, 126.3, 121.2; 31P{1H} NMR δ 5.8; IR 3054 (m), 3017 (m), 2954 (s), 2912 (s),
2850 (s), 2724 (w), 2682 (w), 1954 (w), 1896 (w), 1818 (w), 1776 (w), 1634 (w), 1603
(m), 1582 (w), 1477 (s), 1462 (s), 1430 (m), 1304 (w), 1263 (w), 1210 (w), 1189 (m),
1153 (w), 1137 (m), 1090 (m), 1069 (m), 1027 (m), 1001 (w), 945 (w), 933 (w), 896 (w),
839 (m), 797 (w), 760 (m), 739 (m), 718 (w), 697 (s), 603 (m), 551 (s), 509 (s);
HRMScalc: 391.1490 for C27H22NP; HRMSmeas: 391.1490.
2 1 3 Ph -Ph-2,6-Me2Ph (3c): red liquid (0.383 g, 60.8%); H NMR (600 MHz) δ 7.71 (d, JHH
3 = 9.0 Hz, 1H), 7.49-7.50 (m, 4H), 7.34-7.37 (m, 6H), 7.23 (t, JHH = 7.8 Hz, 1H), 7.21 (d,
3 3 3 3 JHH = 7.2 Hz, 2H), 7.18 (pseudo t, JHH = 7.8 Hz, JHH = 7.2 Hz, 2H), 6.96 (d, JHH = 7.2
3 3 3 Hz, 2H), 6.86 (t, JHH = 7.2 Hz, 1H), 6.38 (dd, JHH = 9.0 Hz, JPH = 1.2 Hz, 1H), 2.06 (s,
13 1 3 1 6H); C{ H} NMR δ 162.7 (d, JPC = 2.6 Hz), 157.3 (d, JPC = 22.0 Hz), 151.6, 138.6 (d,
1 2 2 2 JPC = 19.8 Hz), 135.0 (d, JPC = 20.4 Hz), 134.7 (d, JPC = 9.2 Hz), 133.8 (d, JPC = 9.6
3 3 Hz), 129.8, 129.5 (d, JPC = 8.1 Hz), 129.04, 128.99, 128.8 (d, JPC = 6.8 Hz), 128.4,
126.4, 123.9, 18.7; 31P{1H} NMR δ 5.8; IR 3062 (m), 2926 (s), 2852 (s), 1955 (w), 1887
(w), 1808 (w), 1767 (w), 1615 (m), 1584 (m), 1547 (w), 1458 (s), 1437 (m), 1379 (m),
1305 (w), 1259 (m), 1196 (m), 1133 (w), 1091 (m), 1023 (w), 924 (w), 887 (w), 835 (m),
772 (m), 735 (m), 693 (s), 625 (w), 599 (m); HRMScalc: 419.1803 for C29H26NP;
HRMSmeas: 419.1802.
2 Ph -Ph-2,6-Et2Ph (3d) Method A: red-orange solid (0.466 g, 69.4%); Method B:
orange solid (0.578 g, 57.8%); E-isomer: mp 91-93°C; 1H NMR (600 MHz) δ 7.71 (d,
3 3 JHH = 9.0 Hz, 1H), 7.46-7.50 (m, 4H), 7.36-7.39 (m, 6H), 7.32 (d, JHH = 7.8 Hz, 2H),
3 3 3 7.21 (pseudo t, JHH = 7.8 Hz, JHH = 7.2 Hz, 2H), 7.16 (t, JHH = 7.2 Hz, 1H), 7.00 (d,
63 3 3 3 3 JHH = 6.6 Hz, 2H), 6.95 (t, JHH = 6.6 Hz, 1H), 6.39 (dd, JHH = 9.0 Hz, JPH = 4.8 Hz,
3 3 13 1 1H), 2.39 (q, JHH = 7.8 Hz, 4H), 1.07 (t, JHH = 7.8 Hz, 6H); C{ H} NMR δ 162.4 (d,
3 1 1 2 JPC = 2.7 Hz), 157.3 (d, JPC = 22.0 Hz), 150.7, 138.6 (d, JPC = 19.6 Hz), 135.0 (d, JPC =
2 4 3 20.4 Hz), 134.4 (d, JPC = 20.1 Hz), 133.3, 129.8, 129.4 (d, JPC = 7.6 Hz), 129.0 (d, JPC =
2 31 1 7.8 Hz), 128.8 (d, JPC = 7.6 Hz), 128.5, 128.3, 126.3, 124.2, 24.7, 15.0; P{ H} NMR δ
5.9; IR 3052 (m), 2957 (s), 2915 (s), 2852 (s), 1950 (w), 1892 (w), 1876 (w), 1803 (w),
1615 (s), 1583 (m), 1458 (s), 1374 (m), 1306 (w), 1254 (w), 1186 (m), 1159 (w), 1133
(m), 1091 (m), 1070 (w), 1028 (w), 997 (w), 960 (w), 929 (w), 887 (w), 871 (w), 840 (w),
798 (w), 762 (m), 740 (m), 693 (s), 625 (w), 604 (w); Z-isomer: mp 109-110°C; 1H
3 3 NMR (600 MHz) δ 8.68 (dd, JHH = 9.0 Hz, JPH = 5.4 Hz, 1H), 7.31-7.34 (m, 4H), 7.22-
3 3 3 7.24 (m, 6H), 7.20 (d, JHH = 9.0 Hz, 1H), 7.09 (t, JHH = 7.2 Hz, 1H), 7.06 (pseudo t, JHH
3 3 3 = 7.8 Hz, JHH = 7.2 Hz, 2H), 7.01 (d, JHH = 7.8 Hz, 2H), 7.01 (d, JHH = 7.8 Hz, 2H),
3 3 3 6.97 (t, JHH = 7.8 Hz, 1H), 2.32 (q, JHH = 7.8 Hz, 4H), 1.01 (t, JHH = 7.8 Hz, 6H);
13 1 3 1 2 C{ H} NMR δ 161.8 (d, JPC = 27.4 Hz), 152.4 (d, JPC = 32.0 Hz), 150.6, 141.6 (d, JPC
4 2 1 = 20.1 Hz), 141.1 (d, JPC = 1.6 Hz), 135.3 (d, JPC = 11.0 Hz), 133.7 (d, JPC = 19.8 Hz),
3 2 3 133.4 (d, JPC = 19.4 Hz), 128.9, 128.7 (d, JPC = 6.8 Hz), 128.3 (d, JPC = 1.4 Hz), 127.9,
127.7, 126.3, 124.3, 24.7, 14.9; 31P{1H} NMR δ -7.6; IR 3045 (m), 2961 (s), 2909 (s),
2846 (s), 2720 (w), 2668 (w), 1952 (w), 1889 (w), 1800 (w), 1764 (w), 1669 (w), 1617
(s), 1580 (m), 1460 (s), 1434 (s), 1376 (m), 1340 (w), 1308 (w), 1256 (w), 1224 (w),
1182 (m), 1151 (m), 1093 (m), 1067 (w), 1025 (m), 999 (w), 963 (w), 915 (w), 890 (m),
868 (w), 837 (w), 796 (m), 769 (s), 743 (s), 691 (s), 586 (m); HRMScalc: 447.2116 for
C31H30NP; HRMSmeas: 447.2116.
64 2 i 1 Ph -Ph-2,6- Pr2Ph (3e): yellow crystals (0.528 g, 74.0%); mp 134-135°C; H NMR (600
3 3 MHz) δ 7.68 (d, JHH = 9.6 Hz, 1H) 7.48-7.51 (m, 4H), 7.36-7.37 (m, 6H), 7.32 (d, JHH =
3 3 3 7.2 Hz, 2H), 7.19 (t, JHH = 7.2 Hz, 3H), 7.06 (d, JHH = 7.8 Hz, 2H), 7.02 (t, JHH = 7.8
3 3 3 Hz, 1H), 6.39 (dd, JHH = 9.6 Hz, JPH = 4.8 Hz, 1H), 2.86 (sept, JHH = 7.2 Hz, 2H), 1.09
3 13 1 3 1 (d, JHH = 7.2 Hz, 12H); C{ H} NMR δ 162.6 (d, JPC = 2.6 Hz), 157.6 (d, JPC = 22.2
2 2 3 Hz), 149.4, 138.6 ( JPC = 19.4 Hz), 135.0 (d, JPC = 20.2 Hz), 134.5 (d, JPC = 9.6 Hz),
2 4 3 133.8 (d, JPC = 9.8 Hz), 129.4 (d, JPC = 7.5 Hz), 129.0 (d, JPC = 7.8 Hz), 128.8, 128.7
1 4 31 1 (d, JPC = 20.2 Hz), 128.5, 128.4 (d, JPC = 1.2 Hz), 124.4, 123.2, 28.0, 24.0; P{ H}
NMR δ 4.6; IR 3061 (m), 2916 (s), 2854 (s), 1664 (w), 1612 (s), 1586 (m), 1457 (s),
1436 (m), 1379 (m), 1322 (m), 1259 (w), 1187 (m), 1130 (m), 1099 (m), 1020 (w), 1000
(w), 932 (w), 891 (m), 834 (m), 798 (m), 772 (w), 761 (m), 746 (m), 691 (s); HRMScalc:
475.2429 for C33H34NP; HRMSmeas: 475.2428.
Ph2-tBu-tBu (3f): white solid (0.299 g, 56.7%); mp 94-96°C; 1H NMR (600 MHz) δ
3 3 3 3 7.59 (d, JHH = 9.0 Hz, 1H), 7.36 (dd, JPH = 8.4 Hz, JHH = 7.2 Hz, 4H), 7.30 (t, JHH = 7.2
3 3 3 Hz, 4H), 7.25 (t, JHH = 7.2 Hz, 2H), 6.88 (pseudo t, JPH = 10.2 Hz, JHH = 9.0 Hz, 1H),
13 1 1 3 1.32 (s, 9H), 0.70 (s, 9H); C{ H} NMR δ 159.6 (d, JPC = 27.2 Hz), 158.4 (d, JPC = 2.1
1 2 2 Hz), 137.3 (d, JPC = 15.0 Hz), 136.4 (d, JPC = 6.0 Hz), 131.9 (d, JPC = 18.3 Hz), 128.9
3 2 3 (d, JPC = 5.6 Hz), 128.2, 57.5, 39.9 (d, JPC = 31.0 Hz), 30.2 (d, JPC = 11.1 Hz), 29.5;
31P{1H} NMR δ -20.1; IR 3124 (w), 3072 (m), 3049 (m), 2958 (s), 2901 (s), 2843 (s),
2667 (w), 1958 (w), 1950 (w), 1887 (w), 1864 (w), 1809 (w), 1768 (w), 1742 (w), 1714
(w), 1664 (w), 1652 (w), 1620 (m), 1579 (m), 1542 (w), 1462 (s), 1434 (s), 1376 (m),
1361 (m), 1319 (w), 1296 (w), 1265 (w), 1229 (w), 1216 (m), 1182 (m), 1145 (w), 1109
(w), 1088 (w), 1062 (w), 1020 (w), 995 (w), 953 (w), 930 (w), 885 (w), 844 (w), 798 (w),
65 775 (w), 741 (s), 720 (m), 689 (s), 642 (m), 595 (s), 507 (s); HMRScalc: 351.2116 for
C23H30NP; HRMSmeas: 351.2112.
2 t 1 Ph - Bu-2,6-Me2Ph (3h): yellow liquid (0.401 g, 66.9%); bp >170°C (0.10 mmHg); H
3 NMR (600 MHz) δ 7.54 (d, JHH = 9.0 Hz, 1H), 7.30-7.34 (m, 4H), 7.21-7.25 (m, 6H),
3 3 3 3 7.12 (dd, JPH = 9.6 Hz, JHH = 9.0 Hz, 1H), 6.80 (d, JHH = 7.2 Hz, 2H), 6.74 (t, JHH = 7.2
13 1 3 Hz, 1H), 1.63 (s, 6H), 1.41 (s, 9H); C{ H} NMR δ 164.1 (d, JPC = 2.2 Hz), 163.3 (d,
1 1 2 2 JPC = 29.4 Hz), 151.3, 136.7 (d, JPC = 15.9 Hz), 136.3 (d, JPC = 6.0 Hz), 131.9 (d, JPC =
3 2 18.2 Hz), 128.9 (d, JPC = 5.6 Hz), 128.3, 127.7, 126.4, 123.4, 40.2 (d, JPC = 30.2 Hz),
3 31 1 30.1 (d, JPC = 11.1 Hz), 18.1; P{ H} NMR δ -20.9; IR 3136 (w), 3053 (m), 3021 (m),
2958 (s), 2906 (s), 2836 (s), 2728 (w), 2581 (w), 2026 (w), 1950 (w), 1882 (w), 1809 (w),
1772 (w), 1615 (s), 1579 (s), 1469 (s), 1432 (s), 1385 (m), 1354 (m), 1301 (w), 1259 (m),
1238 (w), 1191 (s), 1150 (m), 1087 (s), 1024 (m), 998 (m), 951 (w), 919 (w), 888 (m),
835 (m), 794 (m), 762 (s), 741 (s), 694 (s), 676 (m), 600 (s), 587 (m); HRMScalc:
399.2116 for C27H30NP; HRMSmeas: 399.2114.
2 t 1 Ph - Bu-2,6-Et2Ph (3i): yellow liquid (0.260 g, 40.5%); H NMR (600 MHz) δ 7.59 (d,
3 3 3 JHH = 9.6 Hz, 1H), 7.34-7.36 (m, 4H), 7.22-7.25 (m, 6H), 7.15 (t, JPH = 9.6 Hz, JHH =
3 3 9.6 Hz, 1H), 6.85-6.86 (m, 3H), 1.93 (q, JHH = 7.8 Hz, 4H), 1.43 (s, 9H), 0.91 (t, JHH =
13 1 3 2 7.8 Hz, 6H); C{ H} NMR δ 163.7 (d, JPC = 2.6 Hz), 150.2, 136.6 (d, JPC = 21.4 Hz),
1 2 1 134.2 (d, JPC = 16.5 Hz), 132.3, 131.9 (d, JPC = 18.2 Hz), 129.2 (d, JPC = 11.8 Hz),
3 2 3 128.9 (d, JPC = 5.7 Hz), 128.3, 125.5, 123.8, 40.3 (d, JPC = 30.6 Hz), 30.1 (d, JPC = 11.1
Hz), 24.2, 14.2; 31P{1H} NMR δ -20.4; IR 3056 (m), 3002 (w), 2961 (s), 2919 (m), 2887
(m), 1922 (w), 1884 (w), 1811 (w), 1612 (s), 1586 (m), 1476 (m), 1450 (m), 1421 (m),
1387 (w), 1356 (w), 1329 (w), 1303 (w), 1256 (w), 1235 (w), 1209 (w), 1183 (m), 1146
66 (w), 1099 (m), 1061 (w), 1026 (m), 1000 (w), 947 (w), 890 (w), 863 (w), 842 (w), 800
(m), 758 (m), 743 (s), 696 (s), 638 (w), 602 (m), 507 (m), 476 (m); HRMScalc: 427.2429
for C29H34NP; HRMSmeas: 427.2433.
2 t i 1 Ph - Bu-2,6- Pr2Ph (3j): yellow liquid (0.302 g, 44.2%); H NMR (600 MHz) δ 7.59 (d,
3 3 3 JHH = 9.6 Hz, 1H), 7.34-7.39 (m, 4H), 7.22-7.25 (m, 6H), 7.18 (t, JPH = 9.6 Hz, JHH =
3 3 9.6 Hz, 1H), 6.92-6.93 (m, 3H), 2.43 (sept, JHH = 6.6 Hz, 2H), 1.43 (s, 9H), 0.92 (d, JHH
13 1 3 1 = 6.6 Hz, 12H); C{ H} NMR δ 162.8 (d, JPC = 3.2 Hz), 162.6 (d, JPC = 29.7 Hz), 153.0
1 2 2 (d, JPC = 39.9 Hz), 148.7, 136.8, 136.5 (d, JPC = 15.0 Hz), 131.9 (d, JPC = 18.2 Hz),
3 2 3 128.9 (d, JPC = 5.7 Hz), 128.8, 124.0, 122.6, 40.4 (d, JPC = 30.0 Hz), 30.2 (d, JPC = 11.0
Hz), 27.5, 23.4; 31P{1H} NMR δ -19.6; IR 3054 (m), 2960 (s), 2866 (m), 1956 (w), 1883
(w), 1810 (w), 1627 (s), 1611 (s), 1585 (m), 1475 (s), 1459 (s), 1433 (s), 1386 (w), 1360
(m), 1323 (w), 1260 (m), 1181 (m), 1145 (w), 1098 (m), 1046 (m), 1020 (m), 920 (w),
889 (w), 836 (w), 800 (m), 742 (s), 721 (m), 695 (s), 643 (w), 596 (m), 569 (m), 506 (s);
HRMScalc: 455.2742 for C31H38NP; HRMSmeas: 455.2741.
2 t 4 Ph -PhMe- Bu (3k): red liquid (0.365 g, 63.1%); NMR (600 MHz) δ 9.13 (d, JPH = 8.4
Hz, 1H), 7.15-7.20 (m, 10H), 6.83-6.91 (m, 3H), 6.63-6.66 (m, 2H), 1.91 (s, 3H), 1.14 (s,
13 1 3 1 2 9H); C{ H} NMR δ 157.3 (d, JPC = 7.0 Hz), 156.9 (d, JPC = 35.1 Hz), 146.2 (d, JPC =
1 3 2 19.8 Hz), 144.5 (d, JPC = 26.4 Hz), 136.4 (d, JPC = 10.8 Hz), 134.6 (d, JPC = 25.0 Hz),
2 4 3 129.3, 128.8 (d, JPC = 11.8 Hz), 128.4 (d, JPC = 3.0 Hz), 128.3 (d, JPC = 7.6 Hz), 127.4,
3 31 1 58.0, 30.0, 17.6 (d, JPC = 3.9 Hz); P{ H} NMR δ -6.0; IR 3135 (w), 3051 (m), 3009
(w), 2968 (s), 2915 (m), 2863 (w), 1950 (w), 1887 (w), 1808 (w), 1761 (w), 1615 (s),
1589 (w), 1479 (m), 1432 (s), 1361 (m), 1306 (w), 1259 (m), 1217 (m), 1154 (w), 1091
(w), 1070 (w), 1023 (s), 955 (w), 929 (w), 913 (w), 892 (w), 845 (w), 798 (m), 777 (w),
67 740 (s), 699 (s), 641 (w), 615 (w); HRMScalc: 385.1959 for C26H28NP; HRMSmeas:
385.1956.
Ph2-PhMe-Ph (3l): yellow solid (0.319 g, 52.4%); mp 152-154°C; 1H NMR (600 MHz)
4 δ 9.45 (d, JPH = 8.4 Hz, 1H), 7.32-7.34 (m, 2H), 7.23-7.25 (m, 5H), 7.18-7.22 (m, 6H),
7.06-7.08 (m, 2H), 6.98-7.01 (m, 3H), 6.60-6.61 (m, 2H), 2.06 (s, 3H); 13C{1H} NMR δ
1 1 2 161.4 (d, JPC = 37.4 Hz), 152.4, 147.9 (d, JPC = 32.4 Hz), 146.7 (d, JPC = 20.0 Hz),
4 2 2 140.2 (d, JPC = 3.0 Hz), 135.9 (d, JPC = 10.0 Hz), 133.8 (d, JPC = 19.5 Hz), 129.3, 128.7,
3 3 128.4 (d, JPC = 6.6 Hz), 127.9, 127.8, 126.5, 126.3, 121.5, 17.5 (d, JPC = 4.0 Hz);
31P{1H} NMR δ -6.0; IR 2948 (s), 2910 (s), 2858 (s), 2722 (w), 2669 (w), 1602 (w), 1576
(m), 1460 (s), 1371 (s), 1309 (w), 1262 (w), 1193 (w), 1152 (w), 1094 (w), 1069 (w),
1021 (m), 968 (w), 921 (w), 879 (w), 843 (w), 801 (w), 764 (m), 738 (m), 717 (m), 691
(m), 633 (m), 610 (s); HRMScalc: 405.1646 for C28H24NP; HRMSmeas: 405.1643.
2 1 Ph -PhMe-2,6-Me2Ph (3m): yellow liquid (0.310 g, 47.7%); H NMR (600 MHz) δ
4 3 9.19 (d, JPH = 8.4 Hz, 1H), 7.17-7.23 (m, 11H), 7.02 (d, JHH = 7.8 Hz, 2H), 6.94-6.97
3 (m, 2H), 6.91 (t, JHH = 7.8 Hz, 1H), 6.65-6.66 (m, 2H), 2.12 (s, 3H), 2.05 (s, 6H);
13 1 1 3 1 C{ H} NMR δ 163.6 (d, JPC = 38.0 Hz), 163.5 (d, JPC = 6.6 Hz), 151.5, 148.2 (d, JPC
2 3 2 = 28.6 Hz), 146.6 (d, JPC = 20.8 Hz), 140.0 (d, JPC = 3.8 Hz), 134.2, 133.8 (d, JPC =
2 3 19.6 Hz), 133.2 (d, JPC = 19.0 Hz), 129.3, 128.7, 128.2, 127.8 (d, JPC = 6.8 Hz), 126.5,
3 31 1 123.8, 18.6, 17.4 (d, JPC = 4.4 Hz); P{ H} NMR δ -6.0; IR 3042 (m), 2926 (s), 2853
(s), 2727 (w), 2674 (w), 1950 (w), 1892 (w), 1808 (w), 1767 (w), 1615 (s), 1589 (m),
1463 (s), 1432 (s), 1374 (m), 1264 (s), 1191 (m), 1091 (s), 1070 (m), 1019 (s), 929 (w),
887 (w), 845 (w), 803 (m), 735 (s), 699 (m), 641 (m); HRMScalc: 433.1959 for
C30H28NP; HRMSmeas: 433.1958.
68 2 1 Ph -PhMe-2,6-Et2Ph (3n): yellow solid (0.404 g, 58.3%); mp 108-109°C; H NMR
4 3 (600 MHz) δ 9.21 (d, JPH = 8.4 Hz, 1H), 7.17-7.22 (m, 11H), 7.04 (d, JHH = 7.8 Hz, 2H),
3 3 7.00 (t, JHH = 7.8 Hz, 1H), 6.78-6.83 (m, 2H), 6.64-6.65 (m, 2H), 2.40 (q, JHH = 7.8 Hz,
3 13 1 1 4H), 2.11 (s, 3H), 1.08 (t, JHH = 7.8 Hz, 6H); C{ H} NMR δ 161.4 (d, JPC = 37.4 Hz),
3 1 2 160.0 (d, JPC = 3.9 Hz), 150.6, 148.1 (d, JPC = 28.6 Hz), 146.9 (d, JPC = 20.8 Hz), 136.0
2 2 3 (d, JPC = 10.2 Hz), 133.8 (d, JPC = 19.8 Hz), 133.1, 128.7, 128.4 (d, JPC = 6.4 Hz),
3 31 1 127.84, 127.83, 126.5, 126.3, 124.1, 25.0, 17.4 (d, JPC = 4.4 Hz), 14.8; P{ H} NMR δ -
6.2; IR 3053 (m), 2917 (s), 2854 (s), 2728 (w), 2676 (w), 1956 (w), 1888 (w), 1809 (w),
1762 (w), 1678 (w), 1616 (m), 1584 (m), 1458 (s), 1432 (m), 1375 (m), 1307 (w), 1260
(m), 1223 (w), 1181 (m), 1155 (w), 1092 (m), 1076 (m), 1024 (m), 966 (w), 919 (w), 883
(w), 862 (w), 840 (w), 799 (m), 768 (m), 737 (s), 720 (m), 694 (s), 637 (w), 516 (s), 480
(s); HRMScalc: 461.2272 for C32H32NP; HRMSmeas: 461.2279.
2 i 1 Ph -PhMe-2,6- Pr2Ph (3o): yellow solid (0.524 g, 71.3%); mp 123-124°C; H NMR
4 3 (600 MHz) δ 9.23 (d, JPH = 8.4 Hz, 1H), 7.18-7.25 (m, 10H), 7.05 (d, JHH = 7.8 Hz, 2H),
3 7.01 (t, JHH = 7.8 Hz, 1H), 6.94-6.97 (m, 2H), 6.87-6.89 (m, 2H), 6.64-6.67 (m, 1H),
3 3 13 1 2.92 (sept, JHH = 7.2 Hz, 2H), 2.13 (s, 3H), 1.11 (d, JHH = 7.2 Hz, 12H); C{ H} NMR δ
1 3 1 163.3 (d, JPC = 38.6 Hz), 163.2 (d, JPC = 6.6 Hz), 149.4, 147.9 (d, JPC = 28.4 Hz), 147.1
2 2 2 (d, JPC = 21.0 Hz), 134.2 (d, JPC = 17.0 Hz), 134.0 (d, JPC = 19.7 Hz), 129.0, 128.8,
3 3 128.6, 128.3 (d, JPC = 6.6 Hz), 127.8, 126.5, 124.3, 123.2, 31.9, 23.0, 17.5 (d, JPC = 4.8
Hz); 31P{1H} NMR δ -6.2; IR 3047 (w), 2955 (s), 2918 (s), 2845 (s), 2726 (w), 2671 (w),
1612 (w), 1584 (w), 1456 (m), 1374 (m), 1305 (w), 1259 (w), 1222 (w), 1181 (w), 1094
(w), 1071 (w), 1021 (w), 925 (w), 884 (w), 796 (w), 764 (w), 742 (w), 696 (m);
HRMScalc: 489.2585 for C34H36NP; HRMSmeas: 489.2582.
69 Ph2-Pen-tBu (3p): yellow-orange crystals (Method C: 2.034 g, 70.00%; Method D:
1 4 1.539 g, 61.56%); mp 105-107°C; H NMR (600 MHz) δ 8.72 (d, JPH = 2.0 Hz, 1H),
3 7.31-7.40 (m, 10H), 2.83 (m, 2H), 2.36 (m, 2H), 1.85 (pent, JHH = 7.6 Hz, 2H), 1.19 (s,
13 1 3 2 1 9H); C{ H} NMR δ 152.8 (d, JPC = 20.2 Hz), 136.8 (d, JPC = 8.6 Hz), 134.6 (d, JPC =
3 1 2 25.6 Hz), 133.4 (d, JPC = 19.0 Hz), 129.1 (d, JPC = 37.2 Hz), 128.7, 128.6 (d, JPC = 6.6
3 2 3 Hz), 57.8, 37.5 (d, JPC = 3.7 Hz), 34.4 (d, JPC = 5.7 Hz), 30.0, 22.8 (d, JPC = 2.1 Hz);
31P{1H} NMR δ -24.7; IR 2719 (w), 2667 (w), 1887 (w), 1825 (w), 1773 (w), 1731 (w),
1700 (m), 1654 (m), 1618 (s), 1576 (m), 1560 (s), 1540 (m), 1431 (s), 1358 (s), 1306 (w),
1275 (w), 1208 (m), 1083 (m), 1026 (w), 995 (w), 964 (w), 891 (m), 824 (m), 787 (m),
746 (s), 694 (s); Anal. Calcd for C22H26NP: C, 78.78; H, 7.81; N, 4.19. Found: C, 78.83;
H, 7.95; N, 4.12.
2 1 Ph -Pen-2,6-Me2Ph (3q): yellow-orange solid (0.618 g, 61.8%); mp 99-100°C; H
4 3 NMR (600 MHz) δ 8.64 (d, JPH = 3.6 Hz, 1H), 7.34-7.38 (m, 10H), 7.00 (d, JHH = 7.8
3 Hz, 2H), 6.90 (t, JHH = 7.8 Hz, 1H), 3.00-3.03 (m, 2H), 2.44-2.46 (m, 2H), 2.04 (s, 6H),
3 3 13 1 3 1.96 (pseudo pent, JHH = 7.8 Hz, JHH = 7.2 Hz, 2H); C{ H} NMR δ 159.8 (d, JPC =
2 1 1 22.0 Hz), 153.1 (d, JPC = 21.4 Hz), 151.7, 150.2 (d, JPC = 22.6 Hz), 136.5 (d, JPC = 8.7
2 3 Hz), 133.4 (d, JPC = 19.4 Hz), 129.0, 128.8 (d, JPC = 6.9 Hz), 128.2 127.2, 123.8, 38.1
3 2 3 31 1 (d, JPC = 4.4 Hz), 34.0 (d, JPC = 5.4 Hz), 22.7 (d, JPC = 2.0 Hz), 18.5; P{ H} NMR δ -
23.2; IR 2961 (s), 2919 (s), 2857 (s), 2720 (w), 1612 (m), 1586 (w), 1455 (s), 1376 (m),
1298 (w), 1240 (w), 1193 (m), 1156 (w), 1088 (w), 1025 (w), 999 (w), 968 (w), 915 (w),
842 (w), 764 (m), 738 (m), 722 (m), 696 (m); HRMScalc: 384.1882 for C26H27NP
+ [M+H] ; HRMSmeas: 384.1874.
70 2 1 Ph -Pen-2,6-Et2Ph (3r): red-orange solid (0.587 g, 58.7%); H NMR (600 MHz) δ 8.67
4 3 3 (d, JPH = 4.2 Hz, 1H), 7.32-7.38 (m, 10H), 7.04 (d, JHH = 7.8 Hz, 2H), 6.99 (t, JHH = 7.8
3 Hz, 1H), 3.00-3.03 (m, 2H), 2.44-2.47 (m, 2H), 2.40 (q, JHH = 7.8 Hz, 4H), 1.96 (pseudo
3 3 3 13 1 pent, JHH = 7.8 Hz, JHH = 7.2 Hz, 2H), 1.07 (t, JHH = 7.8 Hz, 6H); C{ H} NMR δ
3 2 1 159.3 (d, JPC = 21.9 Hz), 153.2 (d, JPC = 21.2 Hz), 150.9, 150.0 (d, JPC = 22.8 Hz),
1 2 3 136.5 (d, JPC = 8.6 Hz), 133.4 (d, JPC = 19.0 Hz), 133.2, 128.9, 128.8 (d, JPC = 6.9 Hz),
3 2 3 126.4, 124.1, 38.1 (d, JPC = 4.5 Hz), 34.1 (d, JPC = 5.4 Hz), 24.9, 22.6 (d, JPC = 1.8 Hz),
15.0; 31P{1H} NMR δ -23.3; IR 3037 (m), 2955 (s), 2922 (s), 2848 (s), 2366 (w), 2324
(w), 2272 (w), 1612 (m), 1581 (w), 1455 (s), 1434 (m), 1372 (m), 1329 (w), 1298 (w),
1261 (w), 1235 (w), 1178 (w), 1099 (w), 1025 (w), 994 (w), 969 (w), 910 (w), 889 (w),
873 (w), 847 (w), 800 (w), 764 (w), 742 (m), 691 (m); HRMScalc: 412.2194 for
+ C28H31NP [M+H] ; HRMSmeas: 412.2205.
2 i 1 4 Ph -Pen-2,6- Pr2Ph (3s): red solid (0.704 g, 70.4%); H NMR (600 MHz) δ 8.72 (d, JPH
3 3 = 3.6 Hz, 1H), 7.35-7.41 (m, 10H), 7.15 (d, JHH = 7.8 Hz, 2H), 7.10 (t, JHH = 7.8 Hz,
3 1H), 3.07-3.09 (m, 2H), 2.92 (sept, JHH = 7.2 Hz, 2H), 2.48-2.51 (m, 2H), 2.01 (pseudo
3 3 3 13 1 pent, JHH = 7.8 Hz, JHH = 7.2 Hz, 2H), 1.14 (d, JHH = 7.2 Hz, 12H); C{ H} NMR δ
3 2 1 159.4 (d, JPC = 22.2 Hz), 153.1 (d, JPC = 21.0 Hz), 150.1 (d, JPC = 23.0 Hz), 149.7,
1 2 3 137.8, 136.5 (d, JPC = 8.8 Hz), 133.3 (d, JPC = 19.2 Hz), 128.9, 128.7 (d, JPC = 6.9 Hz),
3 2 3 124.3, 123.1, 38.1 (d, JPC = 4.6 Hz), 34.1 (d, JPC = 5.4 Hz), 28.1, 23.8, 22.6 (d, JPC = 1.8
Hz); 31P{1H} NMR δ -23.3; IR 3049 (m), 2956 (s), 2914 (s), 2863 (s), 2281 (w), 1954
(w), 1918 (w), 1809 (w), 1757 (w), 1694 (w), 1617 (s), 1580 (m), 1461 (m), 1435 (s),
1378 (w), 1357 (w), 1321 (w), 1259 (w), 1181 (m), 1155 (w), 1093 (m), 1072 (w), 1056
71 (w), 1020 (w), 999 (w), 927 (w), 885 (w), 834 (w), 797 (m), 771 (w), 745 (w), 693 (m),
+ 512 (s), 486 (s); HRMScalc: 440.2507 for C30H35NP [M+H] ; HRMSmeas: 440.2512.
Ph2-Pen-4-tBuPh (3t): yellow solid (0.617 g, 61.7%); mp 150-152°C; 1H NMR (600
4 3 MHz) δ 8.94 (d, JPH = 4.2 Hz, 1H), 7.37-7.40 (m, 4H), 7.34-7.35 (m, 8H), 7.06 (d, JHH =
3 3 8.4 Hz, 2H), 2.95-2.97 (m, 2H), 2.41-2.44 (m, 2H), 1.92 (pseudo pent, JHH = 7.8 Hz, JHH
13 1 3 2 = 7.2 Hz, 2H), 1.31 (s, 9H); C{ H} NMR δ 156.7 (d, JPC = 22.0 Hz), 153.9 (d, JPC =
1 3 2 20.6 Hz), 150.1 (d, JPC = 22.2 Hz), 149.9, 149.4, 133.4 (d, JPC = 18.9 Hz), 128.8 (d, JPC
1 3 = 21.3 Hz), 128.7, 126.18 (d, JPC = 88.0 Hz), 126.17, 121.1, 38.0 (d, JPC = 3.9 Hz), 34.8,
2 3 31 1 34.2 (d, JPC = 5.4 Hz), 31.7, 22.9 (d, JPC = 2.1 Hz); P{ H} NMR δ -24.2; IR 2923 (s),
2858 (s), 1642 (w), 1614 (w), 1581 (w), 1501 (m), 1454 (s), 1375 (s), 1319 (w), 1262
(w), 1216 (w), 1197 (w), 1183 (w), 1089 (w), 1019 (w), 967 (w), 864 (w), 836 (w), 822
(w), 799 (w), 742 (m), 719 (w), 691 (m); HRMScalc: 411.2116 for C28H30NP; HRMSmeas:
411.2119.
2 1 4 Ph -Pen-CH2Ph (3u): red solid (0.816g, 81.6%); H NMR (600 MHz) δ 8.88 (d, JPH =
3.6 Hz, 1H), 7.28-7.44 (m, 15H), 4.73 (s, 2H), 2.88-2.90 (m, 2H), 2.41-2.44 (m, 2H), 1.88
3 3 13 1 1 (pseudo pent, JHH = 7.8 Hz, JHH = 7.2 Hz, 2H); C{ H} NMR δ 159.0 (d, JPC = 87.2
2 1 Hz), 153.2, 142.8, 139.4, 136.2 (d, JPC = 31.2 Hz), 133.1 (d, JPC = 74.4 Hz), 132.8,
3 3 2 128.5 (d, JPC = 28.0 Hz), 128.4, 127.9, 126.8, 65.4, 37.3 (d, JPC = 14.8 Hz), 34.1 (d, JPC
= 23.2 Hz), 22.5 (bs); 31P{1H} NMR δ -25.1; IR 3052 (m), 3028 (m), 2927 (s), 2844 (s),
2730 (w), 2657 (w), 1986 (w), 1955 (w), 1882 (w), 1815 (w), 1768 (w), 1644 (w), 1618
(m), 1602 (m), 1581 (m), 1452 (s), 1436 (s), 1410 (w), 1369 (m), 1338 (m), 1306 (m),
1286 (m), 1260 (w), 1239 (w), 1198 (w), 1177 (w), 1151 (w), 1088 (m), 1068 (m), 1026
72 (m), 995 (m), 912 (w), 887 (w), 839 (w), 798 (w), 741 (s), 720 (s), 694 (s), 611 (m);
HRMScalc: 369.1646 for C25H24NP; HRMSmeas: 369.1648.
2 t 1 4 Ph -Hex- Bu (3v): off-white liquid (0.824 g, 82.4%); H NMR (600 MHz) δ 9.09 (d, JPH
= 3.6 Hz, 1H), 7.32-7.38 (m, 10H), 2.53-2.56 (m, 2H), 1.88-1.90 (m, 2H), 1.63-1.66 (m,
13 1 3 2H), 1.56-1.58 (m, 2H), 1.13 (s, 9H); C{ H} NMR δ 156.4 (d, JPC = 40.2 Hz), 147.6 (d,
2 1 1 2 JPC = 17.7 Hz), 140.7 (d, JPC = 20.4 Hz), 136.7 (d, JPC = 10.8 Hz), 133.6 (d, JPC = 18.9
3 3 2 Hz), 128.6 (d, JPC = 6.3 Hz), 128.6, 57.7, 30.2 (d, JPC = 3.6 Hz), 30.1, 27.0 (d, JPC = 5.8
Hz), 23.7, 22.3; 31P{1H} NMR δ -12.7; IR 3126 (w), 3054 (w), 2962 (s), 2921 (s), 2849
(m), 2664 (w), 2274 (w), 1952 (w), 1885 (w), 1814 (w), 1757 (w), 1618 (s), 1582 (w),
1475 (w), 1448 (w), 1428 (s), 1362 (m), 1326 (w), 1305 (w), 1259 (m), 1202 (s), 1090
(m), 1064 (m), 1023 (m), 961 (w), 900 (w), 843 (w), 802 (m), 740 (s), 694 (s); HRMScalc:
+ 350.2038 for C23H29NP [M+H] ; HRMSmeas: 350.2043.
2 1 Ph -Hex-2,6-Me2Ph (3w): off-white foamy solid (0.523 g, 52.3%); H NMR (600 MHz)
4 3 δ 9.05 (d, JPH = 9.0 Hz, 1H), 7.32-7.35 (m, 10H), 6.98 (d, JHH = 7.2 Hz, 2H), 6.88 (t,
3 JHH = 7.2 Hz, 1H), 2.75-2.78 (m, 2H), 1.96-1.99 (m, 2H), 1.97 (s, 6H), 1.73-1.77 (m,
13 1 3 2 2H), 1.65-1.68 (m, 2H); C{ H} NMR δ 163.0 (d, JPC = 41.2 Hz), 151.7, 147.3 (d, JPC =
1 1 2 18.2 Hz), 145.3 (d, JPC = 23.0 Hz), 136.3 (d, JPC = 11.1 Hz), 133.5 (d, JPC = 19.0 Hz),
3 3 2 128.8 (d, JPC = 4.5 Hz), 128.7, 128.1, 127.3, 123.6, 30.7 (d, JPC = 4.0 Hz), 26.6 (d, JPC =
5.7 Hz), 23.6, 22.2, 18.5; 31P{1H} NMR -12.6; IR 3068 (m), 3057 (m), 3016 (w), 2933
(m), 2860 (m), 2736 (w), 2674 (w), 2362 (w), 2279 (w), 1953 (w), 1880 (w), 1813 (w),
1776 (w), 1750 (w), 1657 (w), 1615 (s), 1589 (m), 1475 (m), 1434 (s), 1372 (w), 1351
(w), 1325 (w), 1304 (w), 1257 (m), 1221 (w), 1190 (m), 1159 (w), 1091 (s), 1065 (m),
73 1024 (s), 915 (w), 889 (w), 842 (m), 801 (s), 764 (m), 744 (s), 723 (m), 697 (s), 601 (w);
+ HRMScalc: 398.2038 for C27H29NP [M+H] ; HRMSmeas: 398.2041.
2 1 Ph -Hex-2,6-Et2Ph (3x): thick green oil (0.544 g, 54.4%); H NMR (600 MHz) δ 9.10
4 3 3 (d, JPH = 9.0 Hz, 1H), 7.35-7.39 (m, 10H), 7.04 (d, JHH = 7.2 Hz, 2H), 7.00 (t, JHH = 7.2
3 Hz, 1H), 2.78-2.81 (m, 2H), 2.36 (q, JHH = 7.8 Hz, 4H), 1.99-2.01 (m, 2H), 1.76-1.80 (m,
3 13 1 3 2H), 1.67-1.70 (m, 2H), 1.04 (t, JHH = 7.8 Hz, 6H); C{ H} NMR δ 162.5 (d, JPC = 41.1
2 1 1 Hz), 150.9, 147.4 (d, JPC = 18.6 Hz), 145.1 (d, JPC = 23.0 Hz), 136.3 (d, JPC = 11.0 Hz),
2 3 133.5 (d, JPC = 19.0 Hz), 133.2, 128.74, 128.73 (d, JPC = 9.6 Hz), 126.3, 123.8, 30.7 (d,
3 2 31 1 JPC = 4.2 Hz), 26.6 (d, JPC = 6.0 Hz), 24.9, 23.6, 22.2, 14.9; P{ H} NMR -12.8; IR
3388 (w), 3133 (w), 3058 (m), 3005 (m), 2964 (s), 2930 (s), 2867 (s), 2675 (w), 2282
(w), 2037 (w), 1949 (w), 1880 (w), 1848 (w), 1806 (w), 1758 (w), 1694 (w), 1614 (s),
1587 (w), 1449 (s), 1433 (s), 1369 (m), 1353 (w), 1327 (m), 1305 (w), 1263 (m), 1236
(w), 1215 (m), 1184 (s), 1156 (w), 1125 (w), 1093 (m), 1066 (m), 1023 (m), 998 (m), 976
(w), 912 (w), 885 (w), 869 (w), 848 (m), 800 (m), 763 (s), 741 (s), 694 (s); HRMScalc:
+ 426.2351 for C29H33NP [M+H] ; HRMSmeas: 426.2349.
2 i 1 Ph -Hex-2,6- Pr2Ph (3y): orange solid (0.773 g, 77.3%); H NMR (600 MHz) δ 9.09 (d,
4 3 3 JPH = 8.4 Hz, 1H), 7.33-7.35 (m, 10H), 7.09 (d, JHH = 7.8 Hz, 2H), 7.05 (t, JHH = 7.8
3 Hz, 1H), 2.84 (sept, JHH = 6.6 Hz, 2H), 2.79-2.82 (m, 2H), 1.97-1.99 (m, 2H), 1.76-1.79
3 13 1 3 (m, 2H), 1.67-1.69 (m, 2H), 1.06 (d, JHH = 6.6 Hz, 12H); C{ H} NMR δ 162.6 (d, JPC
2 1 = 41.4 Hz), 149.7, 147.6 (d, JPC = 18.6 Hz), 145.0 (d, JPC = 23.2 Hz), 137.7, 136.3 (d,
1 2 3 JPC = 11.1 Hz), 133.4 (d, JPC = 19.0 Hz), 128.74, 128.71 (d, JPC = 6.6 Hz), 124.0, 123.1,
3 2 31 1 30.6 (d, JPC = 4.4 Hz), 28.1, 26.7 (d, JPC = 6.0 Hz), 23.7, 22.7, 22.2; P{ H} NMR -
12.9; IR 3388 (w), 3133 (w), 3058 (m), 3005 (m), 2964 (s), 2930 (s), 2867 (s), 2675 (w),
74 2282 (w), 2037 (w), 1949 (w), 1880 (w), 1848 (w), 1806 (w), 1758 (w), 1694 (w), 1614
(s), 1587 (s), 1449 (s), 1433 (s), 1369 (m), 1353 (w), 1327 (m), 1305 (w), 1263 (m), 1236
(w), 1215 (m), 1184 (s), 1156 (w), 1125 (w), 1093 (m), 1066 (m), 1023 (m), 998 (m), 976
(w), 912 (w), 885 (w), 869 (w), 848 (w), 800 (m), 763 (s), 741 (s), 694 (s); HRMScalc:
+ 454.2664 for C31H37NP [M+H] ; HRMSmeas: 454.2681.
2 1 4 Ph -Hex-CH2Ph (3z): orange solid (0.688 g, 68.8%); H NMR (600 MHz) δ 9.31 (d, JPH
= 7.8 Hz, 1H), 7.35-7.38 (m, 10H), 7.28-7.30 (m, 2H), 7.20-7.24 (m, 3H), 4.69 (s, 2H),
2.61-2.63 (m, 2H), 1.92-1.94 (m, 2H), 1.61-1.67 (m, 2H), 1.58-1.61 (m, 2H); 13C{1H}
3 2 1 NMR δ 162.7 (d, JPC = 41.8 Hz), 147.6 (d, JPC = 18.0 Hz), 142.5 (d, JPC = 21.6 Hz),
1 2 3 139.9, 136.4 (d, JPC = 11.0 Hz), 133.6, 133.4 (d, JPC = 18.2 Hz), 128.8, 128.7 (d, JPC =
3 2 6.2 Hz), 128.7, 128.2, 65.3, 30.3 (d, JPC = 3.9 Hz), 27.1 (d, JPC = 5.8 Hz), 23.6, 22.2;
31P{1H} NMR δ -14.3; IR 3053 (w), 3028 (m), 2962 (s), 2944 (s), 2908 (s), 2845 (s),
2717 (w), 2654 (w), 1955 (w), 1878 (w), 1810 (w), 1642 (w), 1615 (m), 1583 (w), 1451
(s), 1433 (m), 1379 (m), 1342 (w), 1324 (w), 1297 (w), 1256 (m), 1220 (w), 1175 (w),
1157 (w), 1088 (m), 1070 (m), 1039 (m), 1021 (m), 939 (w), 912 (w), 864 (w), 862 (w),
798 (m), 735 (m), 694 (s), 617 (w), 522 (s), 499 (s); HRMScalc: 384.1881 for C26H27NP
+ [M+H] ; HRMSmeas: 384.1869.
t 2 t 1 4 Bu -Pen- Bu (3aa): red liquid (0.723 g, 72.3%); H NMR (600 MHz) δ 8.88 (d, JPH =
3 3 6.0 Hz, 1H), 2.84-2.87 (m, 2H), 2.66-2.68 (m, 2H), 1.85 (pseudo pent, JHH = 7.8 Hz, JHH
3 13 1 3 = 7.2 Hz, 2H), 1.22 (s, 9H), 1.18 (d, JPH = 12.0 Hz, 18H); C{ H} NMR δ 155.2 (d, JPC
2 1 2 = 19.8 Hz), 155.0 (d, JPC = 28.4 Hz), 147.1 (d, JPC = 34.7 Hz), 57.4, 39.7 (d, JPC = 6.6
3 1 2 Hz), 33.0 (d, JPC = 5.8 Hz), 32.8 (d, JPC = 19.8 Hz), 30.8 (d, JPC = 14.0 Hz), 30.2, 23.7
(bs); 31P{1H} NMR δ 13.2; IR 2953 (s), 2900 (s), 2848 (s), 2712 (w), 1654 (w), 1618 (m),
75 1560 (w), 1467 (m), 1388 (w), 1361 (m), 1330 (w), 1298 (m), 1257 (m), 1215 (m), 1173
(m), 1094 (m), 1068 (m), 1016 (m), 963 (w), 927 (w), 895 (w), 854 (w), 802 (m), 655
(w), 608 (m); HRMScalc: 295.2429 for C18H34NP; HRMSmeas: 295.2416.
4: yellow solid decomposition product of 2g (0.585 g, 61.9%); mp 151-154°C; 1H NMR
3 3 (600 MHz) δ 9.87 (bs, 1H), 7.46 (pseudo t, JHH = 7.8 Hz, JHH = 7.2 Hz, 2H), 7.38 (t,
3 3 3 3 JHH = 7.2 Hz, 1H), 7.34 (d, JHH = 7.8 Hz, 2H), 7.14 (pseudo t, JHH = 7.8 Hz, JHH = 7.2
3 3 3 Hz, 2H), 7.07 (t, JHH = 7.2 Hz, 1H), 6.70 (d, JHH = 7.8 Hz, 2H), 6.30 (d, JHH = 12.6 Hz,
1H), 1.85 (bs, 2H), 1.46 (s, 9H); 13C{1H} NMR δ 181.4, 152.9, 146.9, 138.8, 131.2,
129.7, 128.7, 126.4, 126.0, 117.9, 91.9, 40.0, 29.7; IR 3443 (w), 3370 (w), 3192 (w),
3087 (w), 2951 (s), 2919 (s), 2846 (s), 1633 (s), 1591 (m), 1523 (s), 1481 (s), 1465 (s),
1360 (m), 1324 (m), 1282 (s), 1256 (m), 1214 (m), 1172 (w), 1093 (m), 1078 (w), 1025
(w), 995 (m), 968 (m), 931 (w), 905 (w), 863 (w), 811 (m), 758 (m), 722 (w), 696 (m);
+ HRMScalc: 278.1783 for C19H22N2 [M-HCl] ; HRMSmeas: 278.1783.
(Ph-Et2Ph)Pd(PPh3)2Cl (5): 2d (0.385 g, 1.29 mmol) in 15 mL of toluene was added to
tetrakis(triphenylphosphine)palladium(0) (1.245 g, 1.077 mmol) in 15 mL of toluene at
0°C. The reaction was warmed to ambient temperature and stirred for an additional 14 h.
The solvent was evaporated, yielding a yellow solid, which was triturated with pentane (3
x 5 mL) and then washed with pentane (3 x 25 mL) to remove free triphenylphosphine.
The solid was dissolved in toluene and precipitated using pentane at -25°C (0.923 g,
1 3 92.3%); mp 227-228°C; H NMR (600 MHz) δ 8.90 (d, JHH = 9.0 Hz, 1H), 7.51-7.59 (m,
12H), 7.29-7.35 (m, 8H), 7.20-7.23 (m, 12H), 6.98-7.03 (m, 3H), 6.92-6.95 (m, 1H),
3 3 3 6.79-6.82 (m, 2H), 6.46 (d, JHH = 9.0 Hz, 1H), 1.88 (q, JHH = 7.8 Hz, 4H), 0.89 (t, JHH =
13 1 3 2 7.8 Hz, 6H); C{ H} NMR δ 167.5, 151.4, 143.8 (d, JPC = 3.0 Hz), 135.24 (d, JPC = 6.3
76 2 2 Hz), 135.16 (d, JPC = 6.3 Hz), 135.06 (d, JPC = 6.3 Hz), 133.0, 130.5 (2C), 129.9, 128.9,
1 1 3 128.4 (d, JPC = 10.6 Hz), 128.3 (d, JPC = 10.6 Hz), 128.22 (d, JPC = 5.1 Hz), 128.19 (d,
3 31 1 JPC = 5.1 Hz), 127.6, 127.2, 125.5, 123.5, 24.5, 13.6; P{ H} NMR δ 24.7; IR 3053 (m),
2948 (s), 2917 (s), 2854 (s), 1636 (w), 1600 (m), 1579 (m), 1542 (w), 1458 (s), 1375 (m),
1338 (w), 1301 (w), 1260 (w), 1232 (w), 1186 (w), 1155 (w), 1092 (m), 1029 (w), 888
(w), 846 (w), 804 (w), 768 (w), 736 (m), 715 (w); Anal. Calcd for C55H50ClNP2Pd · 1
CH2Cl2: C, 66.34; H, 5.18; N, 1.38. Found: C, 66.27; H, 4.76; N, 1.30.
(Ph2-Ph-Ph)Pd(allyl)Cl (7): 3b (0.682 g, 1.74 mmol) in 15 mL of methylene chloride
was added to (allyl)palladiumchloride dimer (0.318 g, 0.871 mmol) in 15 mL of
methylene chloride and stirred for 14 h. Solvent was evaporated, yielding a yellow-
orange solid, which was dissolved in THF and precipitated using pentane at -25°C (0.824
1 3 g, 82.4%); mp 99-101°C; H NMR (600 MHz) δ 8.01 (d, JHH = 9.0 Hz, 1H), 7.67-7.73
3 3 (m, 4H), 7.41-7.46 (m, 6H), 7.34 (d, JHH = 7.2 Hz, 2H), 7.28 (t, JHH = 7.2 Hz, 2H), 7.25
3 3 3 (t, JHH = 7.8 Hz, 3H), 7.17 (t, JHH = 7.8 Hz, 1H), 6.99 (d, JHH = 7.8 Hz, 2H), 6.88 (dd,
3 3 3 3 3 JHH = 9.0 Hz, JPH = 1.8 Hz, 1H), 5.37 (dddd, JHH = 12.0 Hz, JHH = 10.2 Hz, JHH = 7.2
3 3 3 3 Hz, JHH = 6.0 Hz, 1H), 4.72 (t, JHH = 7.2 Hz, JPH = 7.2 Hz, 1H), 3.65 (dd, JPH = 13.8
3 3 3 Hz, JHH = 10.2 Hz, 1H), 2.97 (d, JHH = 6.0 Hz, 1H), 2.39 (d, JHH = 12.0 Hz, 1H);
13 1 3 1 2 C{ H} NMR δ 158.4 (d, JPC = 13.2 Hz), 151.4, 148.4 (d, JPC = 28.4 Hz), 141.3 (d, JPC
2 2 1 = 10.5 Hz), 137.2 (d, JPC = 11.1 Hz), 134.7 (d, JPC = 12.9 Hz), 131.2 (br), 130.4 (d, JPC
3 3 4 = 39.9 Hz), 130.1 (d, JPC = 4.6 Hz), 129.4, 129.0 (d, JPC = 2.2 Hz), 128.8 (d, JPC = 2.0
2 2 31 1 Hz), 128.5, 127.0, 121.3, 117.8 (d, JPC = 5.2 Hz), 80.0 (d, JPC = 30.4 Hz), 61.5; P{ H}
NMR δ 32.3; IR 3045 (m), 2953 (s), 2916 (s), 2852 (s), 2724 (w), 2669 (w), 1597 (w),
1579 (w), 1460 (m), 1437 (m), 1373 (m), 1308 (w), 1263 (w), 1189 (w), 1157 (w), 1134
77 (w), 1093 (m), 1066 (w), 1020 (w), 956 (w), 933 (w), 896 (w), 837 (w), 795 (w), 768 (m),
750 (w), 715 (w), 695 (m), 598 (m); Anal. Calcd for C30H27ClNPPd: C, 62.73; H, 4.74;
N, 2.44. Found: C, 62.40; H, 4.84; N, 2.18.
Crystallography. Summaries of crystal data and collection parameters for crystal structures of 2c-e, 2h, 2j, 2l, 3f, 3p, 4, 5, and 7 are provided in Tables 6-11. Detailed descriptions of data collection, as well as data solution, are provided below. ORTEP diagrams were generated with the ORTEP-3256 software package. For each sample, a
suitable crystal was mounted on a pulled glass fiber using Paratone-N hydrocarbon oil.
The crystal was transferred to a Siemens SMART257 diffractometer with a CCD area
detector, centered in the X-ray beam, and cooled to 140 or 150 K using a nitrogen-flow
low-temperature apparatus that had been precisely calibrated by a thermocouple placed at
the same position as the crystal. An arbitrary hemisphere of data was collected using 0.3°
ω scans, and the data were integrated by the program SAINT.258 The final unit cell parameters were determined by a least-squares refinement of the reflections with I >
10σ(I). Data analysis using Siemens XPREP259 and the successful solution and
refinement of the structure determined the space group. Empirical absorption corrections
were applied for 5 and 7 using the program SADABS.260 Equivalent reflections were
averaged, and the structures were solved by direct methods using the SHELXTL software
package.261 Unless otherwise noted, all non-hydrogen atoms were refined
anisotropically, and hydrogen atoms were included as fixed atoms but not refined.
Compound 2c (Figure 10). X-ray quality crystals were grown from a saturated solution
of pentane at -25°C. The final cycle of full-matrix least-squares refinement was based on
78 3564 observed reflections and 172 variable parameters and converged yielding final residuals: R = 0.0542, Rall = 0.0647, and GOF = 1.071.
Compound 2d (Figure 11). X-ray quality crystals were grown from a saturated solution of pentane at -25°C. The final cycle of full-matrix least-squares refinement was based on
3951 observed reflections and 190 variable parameters and converged yielding final residuals: R = 0.0455, Rall = 0.0532, and GOF = 1.096.
Compound 2e. X-ray quality crystals were grown from a saturated solution of pentane at -25°C. The final cycle of full-matrix least-squares refinement was based on 4574 observed reflections and 208 variable parameters and converged yielding final residuals:
R = 0.0504, Rall = 0.0607, and GOF = 1.049.
Compound 2h (Figure 12). X-ray quality crystals were grown from a saturated solution of pentane at -25°C. The final cycle of full-matrix least-squares refinement was based on
3538 observed reflections and 154 variable parameters and converged yielding final residuals: R = 0.0475, Rall = 0.0511, and GOF = 1.089.
Compound 2j. X-ray quality crystals were grown from a saturated solution of pentane at
-25°C. The final cycle of full-matrix least-squares refinement was based on 9070 observed reflections and 379 variable parameters and converged yielding final residuals:
R = 0.0526, Rall = 0.0822, and GOF = 0.881.
Compound 2l. X-ray quality crystals were grown from a saturated solution of pentane at
-25°C. The final cycle of full-matrix least-squares refinement was based on 3213 observed reflections and 163 variable parameters and converged yielding final residuals:
R = 0.0479, Rall = 0.0512, and GOF = 1.077.
79 Compound 3f. X-ray quality crystals were grown from a saturated solution of pentane at
-25°C. The final cycle of full-matrix least-squares refinement was based on 5349
observed reflections and 226 variable parameters and converged yielding final residuals:
R = 0.0494, Rall = 0.0777, and GOF = 0.967.
Compound 3p. X-ray quality crystals were grown from a layered solution of diethyl
ether and pentane which was cooled to -25 °C. The final cycle of full-matrix least-squares
refinement was based on 3022 observed reflections and 217 variable parameters and
converged yielding final residuals: R = 0.0431, Rall = 0.0504, and GOF = 1.036.
Compound 4. X-ray quality crystals were grown from a saturated solution of pentane at
-25°C. The final cycle of full-matrix least-squares refinement was based on 4576
observed reflections and 208 variable parameters and converged yielding final residuals:
R = 0.0444, Rall = 0.0538, and GOF = 0.979.
Compound 5. X-ray quality crystals were grown from a layered solution of toluene and
pentane at room temperature. One molecule of disordered pentane existed in the
asymmetric unit and was refined isotropically. Hydrogen atoms were included for all
ordered atoms. The final cycle of full-matrix least-squares refinement was based on
20542 observed reflections and 552 variable parameters and converged yielding final
residuals: R = 0.0501, Rall = 0.0714, and GOF = 1.068.
Compound 7. X-ray quality crystals were grown from a layered solution of THF and
pentane at room temperature. The final cycle of full-matrix least-squares refinement was
based on 6421 observed reflections and 307 variable parameters and converged yielding
final residuals: R = 0.0316, Rall = 0.0577, and GOF = 1.047.
80 Table 6. Crystal Data and Collection Parameters
Compound 2c 2d
formula C17H16ClN C19H20ClN fw 269.79 297.85
space group P21/n (#14) P21/n (#14) temperature (K) 140 140 a (Å) 9.813(1) 9.623(1) b (Å) 12.173(1) 13.045(2) c (Å) 12.259(1) 13.049(2) α (deg) 90.000 90.000 β (deg) 102.025(1) 104.102(1) γ (deg) 90.000 90.000 V (Å 3) 1433.6(1) 1588.9(1) Z 4 4 3 densitycalc (g/cm ) 1.250 1.245 diffractometer Siemens SMART Siemens SMART
radiation Mo Kα (λ = 0.71069 Å) Mo Kα (λ = 0.71069 Å) monochromator graphite graphite detector CCD area detector CCD area detector scan type, width ω, 0.3° ω, 0.3° scan speed 20.0 s/frame 15.0 s/frame no. of reflns measd hemisphere hemisphere 2θ range (deg) 4.8-56.4 4.5-56.6 cryst dimens (mm) 0.32 x 0.20 x 0.20 0.34 x 0.34 x 0.28 no. of reflns measd 16425 18046 no. of unique reflns 3564 3951 no. of observations 3564 3951 no. of params 172 190
R, Rw, Rall 0.0542, 0.1591, 0.0647 0.0455, 0.1254, 0.0532 GOF 1.071 1.096
81 Table 7. Crystal Data and Collection Parameters
Compound 2e 2h
formula C21H24ClN C15H20ClN fw 325.91 248.81
space group P21/n (#14) P21/c (#14) temperature (K) 140 140 a (Å) 15.006(2) 9.199(1) b (Å) 8.148(1) 10.798(1) c (Å) 16.118(2) 14.632(1) α (deg) 90.000 90.000 β (deg) 111.492(1) 102.631(1) γ (deg) 90.000 90.000 V (Å 3) 1833.1(1) 1418.4(1) Z 4 4 3 densitycalc (g/cm ) 1.181 1.170 diffractometer Siemens SMART Siemens SMART
radiation Mo Kα (λ = 0.71069 Å) Mo Kα (λ = 0.71069 Å) monochromator graphite graphite detector CCD area detector CCD area detector scan type, width ω, 0.3° ω, 0.3° scan speed 20.0 s/frame 20.0 s/frame no. of reflns measd hemisphere hemisphere 2θ range (deg) 5.4-56.6 4.7-56.6 cryst dimens (mm) 0.50 x 0.20 x 0.16 0.50 x 0.40 x 0.36 no. of reflns measd 21715 16274 no. of unique reflns 4574 3538 no. of observations 4574 3538 no. of params 208 154
R, Rw, Rall 0.0504, 0.1437, 0.0607 0.0475, 0.1286, 0.0511 GOF 1.049 1.089
82 Table 8. Crystal Data and Collection Parameters
Compound 2j 2l
formula C38H56Cl2N2 C16H14ClN fw 611.86 255.76
space group P21/n (#14) Pbca (#61) temperature (K) 140 140 a (Å) 13.365(2) 7.710(1) b (Å) 14.555(1) 17.429(1) c (Å) 19.564(2) 19.171(1) α (deg) 90.000 90.000 β (deg) 106.759(1) 90.000 γ (deg) 90.000 90.000 V (Å 3) 3644.5(1) 2576.6(1) Z 4 8 3 densitycalc (g/cm ) 1.115 1.319 diffractometer Siemens SMART Siemens SMART
radiation Mo Kα (λ = 0.71069 Å) Mo Kα (λ = 0.71069 Å) monochromator graphite graphite detector CCD area detector CCD area detector scan type, width ω, 0.3° ω, 0.3° scan speed 10.0 s/frame 20.0 s/frame no. of reflns measd hemisphere hemisphere 2θ range (deg) 4.3-56.5 4.7-56.6 cryst dimens (mm) 0.46 x 0.24 x 0.20 0.50 x 0.40 x 0.36 no. of reflns measd 37731 29607 no. of unique reflns 9070 3213 no. of observations 9070 3213 no. of params 379 163
R, Rw, Rall 0.0526, 0.1240, 0.0822 0.0479, 0.1318, 0.0512 GOF 0.881 1.077
83 Table 9. Crystal Data and Collection Parameters
Compound 3f 3p
formula C23H30NP C22H26NP fw 351.51 335.41
space group P21/c (#14) P-1 (#2) temperature (K) 150 140 a (Å) 12.993(6) 9.672(2) b (Å) 15.179(8) 10.398(2) c (Å) 11.373(6) 10.748(2) α (deg) 90.000 114.074(3) β (deg) 109.31(1) 91.190(3) γ (deg) 90.000 102.036(3) V (Å 3) 2116.7(2) 958.5(3) Z 4 2 3 densitycalc (g/cm ) 1.103 1.162 diffractometer Siemens SMART Siemens SMART
radiation Mo Kα (λ = 0.71069 Å) Mo Kα (λ = 0.71069 Å) monochromator graphite graphite detector CCD area detector CCD area detector scan type, width ω, 0.3° ω, 0.3° scan speed 30.0 s/frame 10.0 s/frame no. of reflns measd hemisphere hemisphere 2θ range (deg) 4.9-55.3 4.6-56.7 cryst dimens (mm) 0.20 x 0.16 x 0.16 0.80 x 0.15 x 0.10 no. of reflns measd 23789 6057 no. of unique reflns 5349 3022 no. of observations 5349 3022 no. of params 226 217
R, Rw, Rall 0.0494, 0.1448, 0.0777 0.0431, 0.1181, 0.0504 GOF 0.967 1.036
84 Table 10. Crystal Data and Collection Parameters
Compound 4 5
formula C19H23ClN2 ·H2O C55H50ClNP2Pd · 0.6 C5H12 fw 332.91 972.17
space group Pca21 (#29) P2(1)/c (#14) temperature (K) 150 140 a (Å) 11.122(1) 18.314(1) b (Å) 8.103(1) 10.929(1) c (Å) 20.343(1) 24.314(1) α (deg) 90.000 90.000 β (deg) 90.000 99.009(1) γ (deg) 90.000 90.000 V (Å 3) 1833.5(2) 4807.0(1) Z 4 4 3 densitycalc (g/cm ) 1.206 1.303 diffractometer Siemens SMART Siemens SMART
radiation Mo Kα (λ = 0.71069 Å) Mo Kα (λ = 0.71069 Å) monochromator graphite graphite detector CCD area detector CCD area detector scan type, width ω, 0.3° ω, 0.3° scan speed 30.0 s/frame 30.0 s/frame no. of reflns measd hemisphere hemisphere 2θ range (deg) 6.2-54.0 4.5-67.8 cryst dimens (mm) 0.20 x 0.14 x 0.06 0.45 x 0.26 x 0.06 no. of reflns measd 20887 61781 no. of unique reflns 4576 20542 no. of observations 4576 20542 no. of params 208 552
R, Rw, Rall 0.0444, 0.1075, 0.0538 0.0501, 0.1146, 0.0714 GOF 0.979 1.068
85 Table 11. Crystal Data and Collection Parameters
Compound 7
Formula C30H27ClNPPd fw 574.42 space group P-1 (#2) temperature (K) 140 a (Å) 9.923(1) b (Å) 12.152(1) c (Å) 12.453(1) α (deg) 108.390(2) β (deg) 104.282(2) γ (deg) 104.625(2) V (Å 3) 1288.8(2) Z 2 3 densitycalc (g/cm ) 1.480 diffractometer Siemens SMART
radiation Mo Kα (λ = 0.71069 Å) monochromator graphite detector CCD area detector scan type, width ω, 0.3° scan speed 15.0 s/frame no. of reflns measd hemisphere 2θ range (deg) 4.5-56.6 cryst dimens (mm) 0.30 x 0.30 x 0.20 no. of reflns measd 15217 no. of unique reflns 6421 no. of observations 6421 no. of params 307
R, Rw, Rall 0.0316, 0.0795, 0.0577 GOF 1.047
86 Figure 10. ORTEP diagram (50% thermal ellipsoids) of PhCCl=CHCH=N(2,6-
Me2C6H3) (2c). Hydrogen atoms omitted for clarity. Bond lengths (in Å): N1-C1 =
1.272(2), C1-C2 = 1.452(2), C2-C3 = 1.335(2), C3-Cl1 = 1.744(2). Bond angles (in deg): C1-N1-C10 = 117.2(2), N1-C1-C2 = 121.6(2), C1-C2-C3 = 124.8(2), C2-C3-
Cl1 = 118.7(1).
Figure 11. ORTEP diagram (50% thermal ellipsoids) of PhCCl=CHCH=N(2,6-
Et2C6H3) (2d). Hydrogen atoms omittted for clarity. Bond lengths (in Å): N1-C1 =
1.273(2), C1-C2 = 1.451(2), C2-C3 = 1.336(2), C3-Cl1 = 1.739(1). Bond angles (in deg): C1-N1-C10 = 116.1(1), N1-C1-C2 = 121.5(1), C1-C2-C3 = 125.3(1), C2-C3-
Cl1 = 118.3(1).
87 Figure 12. ORTEP diagram (50% thermal ellipsoids) of tBuCCl=CHCH=N(2,6-
Me2C6H3) (2h). Hydrogen atoms omitted for clarity. Bond lengths (in Å): N1-C1 =
1.271(2), C1-C2 = 1.455(2), C2-C3 = 1.337(2), C3-Cl1 = 1.752(1). Bond angles (in
deg): C1-N1-C8 = 116.6(1), N1-C1-C2 = 120.5(1), C1-C2-C3 = 126.0(1), C2-C3-Cl1 =
118.9(1).
II-4: Conclusion
A large library of α,β-unsaturated 3-iminophosphine ligands was synthesized in a high-yielding, three step process. Steric bulk was easily added and removed from the imine moiety by simply choosing a different primary amine for the condensation step.
The first generation α,β-unsaturated β-chloroimines mostly displayed high stability, whereas the second generation readily decomposed after a few days. However, there was no observed decomposition of the α,β-unsaturated 3-iminophosphine ligands once they were isolated. The stereochemistry around the carbon-carbon double bond was determined by collecting the solid state structure of various α,β-unsaturated β- chloroimines and 3-iminophosphines. Compounds 3a-e adopted an E arrangement when synthesized by diphenyl(trimethylsilyl)phosphine and a nickel catalyst, even though their
α,β-unsaturated β-chloroimine precursors displayed a Z arrangement. It was believed that this change in arrangement occurred because of an isomerization during the formation of the carbon-phosphorus bond. However, the Z-isomer of 3d could be prepared by the
88 reaction of α,β-unsaturated β-chloroimine 2d with lithium diphenylphosphide in very cold and dilute conditions. 3f-j were Z-isomers, as displayed by Figure 13, whereas 3k-o adopted an E stereochemistry due to the high stability of this isomer during the enol tautomerization. Compounds 3p-aa were believed to adopt a Z-isomer arrangement due to the cyclic ring system and this assignment was confirmed by Figure 14 as well as the solid state structures of their respective palladium(II) chloride complexes (see Chapter 3).
89
Chapter 3:
──────────────────────────────
Synthesis, Isolation, and Characterization of
3-Iminophosphine Palladium(II) Complexes
──────────────────────────────
90 III-1: Introduction
In the last century, research involving palladium has revealed an amazingly
diverse reactivity for this metal. With access to reaction pathways involving oxidative addition, reductive elimination, insertion, transmetallation, and β-elimination (hydride,
carbon, or other heteroatoms), palladium proves to be among the most versatile transition
metals.2 Furthermore, palladium complexes have shown broad utility in catalytic
coupling reactions and are often tolerant to a wide range of substrate functional groups.2
This balance of stability and reactivity is ideal for building a catalyst system. Thus far, a wide variety of palladium catalysts have been developed and commercialized.262 The primary limitations of currently available palladium catalysts involve electronic factors, often reducing substrate scope. This difficulty is not due to catalyst instability but is a result of both catalytic activity (kinetics) and selectivity.
For over a decade, it has been recognized that ligands capable of hemilability play a special role in catalysis.210-215 The term hemilability refers to a chelating ligand’s
ability to partially decoordinate from a metal center, freeing binding sites for further
reactivity while remaining attached to the transition metal. This can be especially useful
in stabilizing catalytic intermediates, as the proximity of the ligand’s unutilized donor
atoms can help prevent decomposition of highly reactive intermediates within a catalytic
cycle. Key aspects in the design of hemilabile ligands include reduced ligand symmetry
and steric or electronic factors that favor one donor atom over another within the ligand
framework.
In an effort to couple the stability and reactivity of palladium complexes with the
benefits of a robust hemilabile ligand framework, a variety of α,β-unsaturated 3-
91 iminophosphine ligands were coordinated to commercially available palladium(II)
sources. The resulting complexes have sterically protected metal centers with unique
electronic properties. Electronic changes were then incorporated into these complexes by
salt metathesis, alkylation, or coordination reactions in order to better understand the
inherit reactivity and stability of 3-iminophosphine ligated palladium complexes.
III-2: Results and Discussion
1st Generation Palladium Complexes
The syntheses of (3IP)PdCl2 (8a-c) were readily achieved by simple coordination
of the corresponding 3-iminophosphine ligand (3b, 3c, or 3f) to anhydrous palladium(II) chloride (Scheme 20). It is believed that complexes 8a and 8b adopted an η1 coordination mode through the phosphorus donor atom due to the diastereomeric arrangement of the aldimine with respect to the phosphorus moiety. Compound 8c was believed to display an η2-ligand coordination due to the upfield shifts in the imine proton
and phosphorus resonances, which was allowed due to the Z conformation of the 3-
iminophosphine ligand. Several features of these complexes merit further attention. The
31P NMR resonances appear downfield from their corresponding free ligand resonances,
and the observed shifts were observed to be independent of the isomer used. Moreover,
t Ph Ph Ph Bu Ph Cl Ph Ph P P Cl PdCl2 Pd P + Pd Cl N Cl R NR' Ph NAr tBu
3b-c, 3f 8a-b 8c
Scheme 20. Coordination of 1st generation 3-iminophosphines to palladium(II)
chloride (R = phenyl, tert-butyl; Ar = phenyl, 2,6-dimethylphenyl).
92 the 8c imine proton resonance was significantly more shielded than those of 8a and 8b
due to its η2 coordination to the palladium and therefore appeared further upfield. In
contrast, the vinylic proton resonances of 8a and 8b appeared around 10.4 ppm,
indicative of a highly deshielded species.
2nd Generation Palladium Complexes
The second generation 3-iminophosphine ligands, those with a cyclic ring as part
of the vinylic backbone, were coordinated to palladium(II) by reaction with an equivalent
of anhydrous PdX2, where X = Cl or Br (Scheme 21). These complexes (9a-m) displayed η2-ligand coordination, as evident by the upfield shift of the imine proton and
downfield shift of the phosphorus resonances. The coordination mode of the ligands was
confirmed by X-ray crystallography for several complexes (9a, 9h, 9m; Figures 13-15).
Because the related complexes displayed similar 1H, 13C, and 31P resonances with only
minor differences attributable to differing steric and electronic features of each ligand
except for 9h, it was concluded that the ligand adopts an η2 confirmation in each of these
species (9a-9m). Moreover, only minor changes were observed when the chloro ligands
were substituted with bromo ligands, as evident when compound 9a was compared to 9b.
An alternate route to 9b involved the reaction of 9a with two equivalents of lithium
R' R' R R' R' NP P X PdX2 Pd n N X n R
3p-aa 9a-m Scheme 21. Coordination of 2nd generation 3-iminophosphines to palladium(II)
halide (X = Cl, Br; n = 1, 2; R = alkyl, aryl; R’ = phenyl, tert-butyl).
93 Figure 13. ORTEP diagram (50% thermal ellipsoids) of 9a. Hydrogen atoms and disordered methylene chloride molecules omitted for clarity. Bond lengths (in Å):
Pd1-P1 = 2.22(1), Pd1-N1 = 2.065(4), N1-C1 = 1.285(6), C1-C2 = 1.463(6), C2-C3 =
1.351(6). Bond angles (in deg): P1-Pd1-N1 = 85.3(7), Cl1-Pd1-Cl2 = 90.9(7), N1-
C1-C2 = 123.6(2), C1-C2-C3 = 124.1(9).
Figure 14. ORTEP diagram (50% thermal ellipsoids) of 9h. Hydrogen atoms and disordered methylene chloride molecules omitted for clarity. Bond lengths (in Å):
Pd1-P1 = 2.220(1), Pd1-N1 = 2.050(3), N1-C1 = 1.273(4), C1-C2 = 1.469(5), C2-C3
= 1.362(5). Bond angles (in deg): P1-Pd1-N1 = 84.7(1), Cl1-Pd1-Cl2 = 90.8(1), N1-
C1-C2 = 125.9(3), C1-C2-C3 = 120.4(3).
94 Figure 15. ORTEP diagram (50% thermal ellipsoids) of 9m. Hydrogen atoms and
methylene chloride molecule omitted for clarity. Bond lengths (in Å): Pd1-P1 =
2.285(1), Pd1-N1 = 2.046(3), N1-C1 = 1.280(5), C1-C2 = 1.452(5), C2-C3 =
1.351(5). Bond angles (in deg): P1-Pd1-N1 = 92.4(1), Cl1-Pd1-Cl2 = 85.1(1), N1-
C1-C2 = 128.1(3), C1-C2-C3 = 128.2(4). bromide. This reaction proceeded rapidly with quantitative conversion. The driving force of this substitution likely derives from the high lattice energy of the byproduct, lithium chloride, as well as improved orbital overlap between the palladium and the bromide ligands compared to that observed with the chloride ligands. The lone exception to the structural assignment was 9h. Spectroscopic measurements identified the presence of two η2 isomers present in solution, one bound through the phosphorus and nitrogen donor atoms, as shown in Figure 14, and the other believed to be bound through the phosphorus and alkenyl carbons. Unlike all of the other dichlorides synthesized in this dissertation, 9h was only sparingly soluble in deuterated chloroform and therefore complete identification spectroscopically was accomplished using deuterated pyridine.
While resonances for the isomer bound through the phosphorus/nitrogen atoms were similar to those observed in the series, resonances for the other isomer appeared further
95 downfield, especially those pertaining to the alkenyl ring and imine. The phosphorus
resonance was shifted upfield in the case of the phosphorus/alkenyl isomer due to the
increased shielding of the metal.
The 3-iminophosphine ligand also readily coordinated to palladium supplied as
the (allyl)palladium(II) chloride dimer (Scheme 22). The resulting complexes (10a-b)
were found to contain an η1-ligand coordinated through its phosphorus donor atom, with
the remainder of the palladium’s coordination sphere fulfilled by chloro and η3-allyl ligands (Figure 16). In an effort synthesize an η2-3-iminophosphine palladium complex,
the chloride of 10a was replaced with a weakly coordinating anion, such as triflate, tetrakis(pentafluorophenyl)borate or hexafluorophosphate. As a result, the 3- iminophosphine ligand adopted an η2 conformation, with the remainder of palladium’s
coordination sphere fulfilled by the η3-allyl ligand. This was achieved by two different
pathways. In the first, treatment of 10a with either silver triflate or lithium
tetrakis(pentafluorophenyl)borate led to the loss of metal chloride and concomitant formation of the ionic species [(3IP)Pd(allyl)][Y], where Y is either OTf (11a) or
B(C6F5)4 (11b). By layering a tetrahydrofuran solution of 11a with pentane, crystals
suitable for X-ray structure determination were produced. The solid state structure
t Bu + Ph P N N P P 2 i MY - Pd Pd [Y] -MCl Cl N 3p 10a 11a-c
Scheme 22. Coordination of 2nd generation 3-iminophosphine to (allyl)palladium(II)
chloride and subsequent salt metathesis. i) 0.5 eq. [(allyl)PdCl]2, CH2Cl2. ii) M = Ag,
Li, NH4; Y = OTf, B(C6F5)4, PF6.
96 Figure 16. ORTEP diagram (50% thermal ellipsoids) of 10a. Hydrogen atoms
omitted for clarity. Bond lengths (in Å): Pd1-Cl1 = 2.378(5), Pd1-P1 = 2.308(8),
Pd1-C23 = 2.202(3), Pd1-C25 = 2.101(4), N1-C1 = 1.269(7), C1-C2 = 1.460(4), C2-
C3 = 1.346(6). Bond angles (in deg): P1-Pd1-Cl1 = 101.7(2), C23-Pd1-C25 =
67.7(3), P1-Pd1-C23 = 163.4(3), P1-Pd1-C25 = 95.9(3).
revealed an ionic species, in which the square-planar palladium is coordinated by an η2-3-
iminophosphine ligand and an η3-allyl ligand with an outer-sphere triflate anion (Figure
17). Based on the strong similarities in their NMR spectra, it was postulated that 11b has
an analogous coordination environment at the palladium center. A more attractive route
to similar complexes is through the treatment of 10a with ammonium salts.263, 264 The
reaction of 10a with ammonium hexafluorophosphate yielded the ionic species
[(3IP)Pd(allyl)][PF6] (11c). Once again, similar NMR shifts were observed for 11c;
however, two isomers were present in a 10:3 ratio by 1H NMR integration. These
isomers were the result of the geometric arrangement of the allylic substituent with
respect to the cyclopentenyl ring. The allyl group can be considered to point in a certain direction, as indicated by the CH vector of its central carbon atom. In addition, the 5- membered chelate ring of the ligand is not planar, but rather puckered with the
97 Figure 17. ORTEP diagram (50% thermal ellipsoids) of 11a. Triflate anion and
hydrogen atoms omitted for clarity. Bond lengths (in Å): Pd1-P1 = 2.267(5), Pd1-N1
= 2.141(3), Pd1-C23 = 2.238(5), Pd1-C25 = 2.102(4), N1-C1 = 1.284(1), C1-C2 =
1.465(4), C2-C3 = 1.342(3). Bond angles (in deg): P1-Pd1-N1 = 92.9(5), C23-Pd1-
C25 = 67.0(6).
cyclopentenyl ring centered above or below the palladium coordination plane. Thus, two
distinct isomers exist, denoted cis and trans, indicating that the CH vector and the cyclopentenyl ring are on the same or opposite sides of the square plane of palladium
coordination. The isomer assignment was supported by two dimensional NMR
experiments. Moreover, the solid state structure of 11c was obtained and revealed that
the two distinctive isomers co-crystallized, confirming these conclusions (Figure 18).
The affinity of amine ligands towards palladium complexes containing the 3-
iminophosphine ligand was important because one of the goals of the project was late-
transition metal catalyzed hydroamination, in particular hydroamination of alkenes,
dienes, and alkynes. To establish whether there was a correlation between amine
coordination to the palladium center and catalytic activity, a series of reactions, utilizing
9a as the palladium metal complex, with a variety of primary and secondary amines were
98
cis-isomer trans-isomer
Figure 18. ORTEP diagram (50% thermal ellipsoids) of the cationic portions of 11c.
The central carbon of the allyl group bound to Pd1 is disordered over two positions in
a 1:1 ratio, giving a 1:1 ratio of cis/trans isomers in this half of the asymmetric unit.
Hydrogen atoms and hexafluorophosphate ions have been omitted for clarity. Bond
lengths (in Å): Pd1-P1 = 2.267(2), Pd1-N1 = 2.160(5), Pd2-P2 = 2.262(2), Pd2-N2 =
2.144(6). Bond angles (in deg): P1-Pd1-N1 = 90.2(1), P2-Pd2-N2 = 87.7(2).
performed. Generally, hydroamination is thought to proceed via nucleophilic attack of an
amine on a coordinated alkene or alkyne; however, if catalytic activity is inverse to
nucleophilicity, amine coordination to the metal center prior to carbon-nitrogen bond
formation may explain this phenomenon.147, 161, 164, 192 Also, this amine coordination
could be an important step in the mechanism for catalytic aryl amination, a similar
process to hydroamination. Therefore, a variety of amines were reacted with 9a to yield
the corresponding (3IP)PdCl2(amine) complexes (12a-l; Scheme 23). The reaction proceeded readily in almost any solvent, including chloroform, dichloromethane,
99 P Cl N P Cl Pd + HNRR' Pd N Cl Cl NHRR' 9a 12a-l
Scheme 23. Amine coordination. HNRR’ = diethylamine (12a), morpholine (12b),
piperidine (12c), N-methyl-butylamine (12d), di-n-butylamine (12e), dibenzylamine
(12f), pyrrolidine (12g), diisopropylamine (12h), cyclohexylamine (12i), tert-
butylamine (12j), p-toluidine (12k), benzylamine (12l). tetrahydrofuran, diethyl ether, and toluene; however, the reaction rate is correlated to the solubility of the initial palladium complex in the reaction solvent. The observed NMR spectra were suggestive of η1 coordination by the 3-iminophosphine ligand in the product complexes, as evidenced by the significant downfield shift of the aldimine proton, while the phosphorus shift moved only slightly upfield. The solid state structure of 12a confirmed the suspected coordination environment of the palladium, revealing trans chloride ligands, a coordinated diethylamine, and the η1-3-iminophosphine ligand bound only through the phosphorus donor atom (Figure 19). Ultimately, it was found that this reaction was general to virtually every amine tested, and so a series of these complexes with differing electronic and steric properties were synthesized, all displaying similar
NMR shifts. In general, for aliphatic amines, coordination appeared to be independent of amine basicity and steric bulk. It is perhaps most revealing to discuss those amines that did not undergo this reaction readily, specifically aryl amines. Two representative aryl amines, p-toluidine and 2,6-diethylaniline, were used to investigate this coordination reaction. The coordination of p-toluidine proceeds very slowly, only achieving 51% completion, even after extensive heating at 100°C. No reaction at all was observed for
100 Figure 19. ORTEP diagram (50% thermal ellipsoids) of 12a. Other than the amine,
hydrogen atoms have been omitted for clarity. Bond lengths (in Å): Pd1-Cl1 =
2.298(1), Pd1-Cl2 = 2.306(1), Pd1-P1 = 2.246(1), Pd1-N2 = 2.211(2), N1-C1 =
1.267(3), C1-C2 = 1.460(3), C2-C3 = 1.338(3), N2-C24 = 1.479(3), N2-C25 =
1.476(3). Bond angles (in deg): P1-Pd1-N2 = 177.0(1), P1-Pd1-Cl1 = 95.3(1), P1-
Pd1-Cl2 = 86.6(1), Cl1-Pd1-Cl2 = 177.4(1), C23-C24-N2 = 111.9(2), C24-N2-C25 =
111.2(2), N2-C25-C26 = 111.9(2).
2,6-diethylaniline, even when the reaction was heated to 60°C for several days. The reduced basicity of these aryl amines clearly hampers their ability to coordinate to the palladium center. In the case of the 2,6-diethylaniline, the lower basicity, coupled to its extensive steric bulk, completely prohibit its coordination. Thus, we conclude that there is little or no correlation between hydroamination catalytic activity and the amine’s ability to coordinate to the palladium metal center since good yields were observed for hydroamination with aryl amines (see Chapter 4).
Another important step in the catalytic hydroamination of unsaturated carbon- carbon bonds involves binding of the unsaturated substrate to an electrophilic metal center. It is important that the electron density from the carbon-carbon multiple bond be
101 transferred to the metal as a means of activating this species towards carbon-nitrogen bond formation.265 Generally speaking, when the metal center is more electrophilic, the
alkene/alkyne binds more strongly, creating a more reactive catalyst. Thus, a series of
highly electrophilic 3-iminophosphine palladium(II) complexes were synthesized
(Scheme 24). The synthesis of a mono-chloro, mono-triflato palladium complex (13a)
was achieved by the reaction of 9a with one equivalent of silver triflate. This reaction
proceeded through a standard salt metathesis reaction pathway, where the silver cation
removes a chloride from the palladium. There are significant downfield shifts in the 1H
NMR spectrum for all the protons except for those associated with the methylene bridge of the cyclopentenyl ring. Moreover, the phosphorus resonance is also shifted downfield appreciably. The solid state structure of 13a revealed a dimer with two chlorides bridging two palladium centers, along with two outer sphere triflate anions (Figure
20).266-268 The analogous mono-bromo, mono-triflato palladium complex (13b) was synthesized in a similar fashion and displayed very similar spectroscopic data to that of
13a, consistent with a similar dimeric structure. To further enhance the electrophilicity of these complexes, the remaining halide was replaced with another triflate counterion.
Amazingly, the resultant complex proved to be isolable, with no evidence of decomposition to palladium black or other likely byproducts. The product,
2+ P X P X N P OTf AgOTf 1 - AgOTf Pd Pd Pd . 2 [OTf] Pd -AgX 2 -AgX N X N X P N OTf 9a-b 13a-b 14
Scheme 24. Salt metathesis of 9; X = Cl (9a, 13a), Br (9b, 13b).
102 Figure 20. ORTEP diagram (50% thermal ellipsoids) of the cationic portion of 13a.
t Hydrogen atoms, disordered Bu carbon atoms, CH2Cl2 molecule, and triflate ions
have been omitted for clarity. Bond lengths (in Å): Pd1-P1 = 2.215(2), Pd-Cl1 =
2.326(2), Pd1-Cl2 = 2.468(2), Pd1-N1 = 2.080(5), Pd2-P2 = 2.020(2), Pd2-N2 =
2.045(5), Pd2-Cl1 = 2.446(2), Pd2-Cl2 = 2.327(2). Bond angles (in deg): P1-Pd1-N1
= 89.4(1), P1-Pd1-Cl1 = 89.9(1), P1-Pd1-Cl2 = 165.6(1), N1-Pd1-Cl1 = 172.7(1), N1-
Pd1-Cl2 = 99.4(1), P2-Pd2-N2 = 88.3(2), P2-Pd2-Cl1 = 166.1(1), P2-Pd2-Cl2 = 93.0
(1), N2-Pd2-Cl1 = 97.1(2), N2-Pd2-Cl2 = 172.7(2).
(3IP)Pd(OTf)2 (14) can be synthesized by either adding one equivalent of silver triflate to
13a or by adding two equivalents to 9a. Compound 14 displayed similar NMR
resonances to 9a, which was suggestive of a similar coordination environment. To
confirm this assertion, X-ray quality crystals were grown, and the solid state structure confirmed the η2 coordination of the 3-iminophosphine ligand as well as two inner sphere
triflate anions (Figure 21).269-271
The versatility and stability of halogenated palladium(II) compounds are excellent
attributes for their synthesis and isolation. However, the lack of hydroamination catalytic
103 activity in these halide-containing species leads to a desire to have different anions
present. We expect that the incorporation of triflate anion(s) will enhance the reactivity
of the 3-iminophosphine palladium complexes because of the increased electrophilicity of the metal, which would allow for stronger binding of substrates. Moreover, it is suspected that compound 14 will display similar amine coordination chemistry to that of compound 9a, although it is unclear how the amine binding will affect the coordination environment of the palladium.
One final class of compounds of interest herein includes those in which palladium-alkyl bonds are present. Palladium-alkyl complexes are relevant not only to hydroamination but also to a wide variety of other cross-coupling reactions commonly catalyzed by palladium species.2, 94, 200, 206, 207 In addition, palladium-alkyls often undergo
Figure 21. ORTEP diagram (50% thermal ellipsoids) of 14. Hydrogen atoms have
been omitted for clarity. Bond lengths (in Å): Pd1-P1 = 2.194(1), Pd1-N1 =
2.016(2), Pd1-O1 = 2.155(2), Pd1-O4 = 2.064(2), N1-C1 = 1.288(3), C1-C2 =
1.452(3), C2-C3 = 1.341(3). Bond angles (in deg): P1-Pd1-N1 = 86.1(1), P1-Pd1-O1
= 174.4(1), P1-Pd1-O4 = 92.4(1), O1-Pd1-O4 = 86.9(1), O1-Pd1-N1 = 94.7(1), N1-
C1-C2 = 125.7(2), C1-C2-C3 = 125.0(2), C2-C3-P1= 120.2(2).
104 insertion reactions leading to the formation of alternative functional groups such as acyls and carboxylates. Moreover, the weaker palladium-carbon bond is more susceptible to cleavage than the corresponding palladium-chloride bond. Alkylation of 9a was readily achieved using two different synthetic routes (Scheme 25); (3IP)Pd(CH3)Cl (15a) was synthesized by reacting 9a with either methyllithium or tetramethyltin. The appearance of a doublet in the 1H NMR spectrum, as well as a significant shift in the phosphorus resonance, was indicative of alkylation. Also, the imine proton resonance was found
P Cl P CH3 P CH3 i AgOTf Pd Pd Pd -AgCl N Cl N Cl N OTf 9a 15a 16
Scheme 25. Alkylation of 9a. i) Sn(CH3)4, CH2Cl2, 30 h or CH3Li, THF, -78°C →
22°C, 14 h. below 8.00 ppm, suggestive of η2 coordination. The solid state structure of 15a confirmed the η2 coordination of the 3-iminophosphine ligand and showed that the methyl group was located trans to the nitrogen donor atom (Figure 22). In contrast, when the methylating agent used was methyllithium complexed with lithium bromide, an anion exchange was observed in addition to methylation, ultimately leading to the isolation of
(3IP)Pd(CH3)Br (15b). A more straightforward synthesis of 15b was achieved by reacting 9b with either methyllithium or tetramethyltin (Scheme 26). Furthermore, 15b could also be produced by the reaction of 15a with one equivalent of lithium bromide,
P CH3 P CH3 P Br LiBr (CH3)4Sn Pd Pd Pd -LiCl -(CH3)3SnBr N Cl N Br N Br 15a 15b 9b
Scheme 26. Synthesis of 15b.
105
Figure 22. ORTEP diagram (50% thermal ellipsoids) of 15a. Hydrogen atoms have
been omitted for clarity. Bond lengths (in Å): Pd1-P1 = 2.196(1), Pd1-N1 =
2.212(2), Pd1-Cl1 = 2.389(1), Pd1-C23 = 2.034(2), N1-C1 = 1.274(3), C1-C2 =
1.463(3), C2-C3 = 1.346(3). Bond angles (in deg): P1-Pd1-N1 = 84.9(1), P1-Pd1-
C23 = 93.3(1), C23-Pd1-Cl1 = 87.3(1), Cl1-Pd1-N1 = 95.1(1).
which is believed to be the reaction that occurs if methylation of 9a is attempted with
methyllithium complexed with lithium bromide. With these alkylated species isolated,
the traits of alkyl complexes and weakly coordinating counterions were combined to
produce a highly electrophilic palladium-alkyl complex. Substitution of the chloride for
a weakly coordinating triflate anion was again accomplished by reacting 15a with one
equivalent of silver triflate in a standard salt metathesis reaction to produce
(3IP)Pd(CH3)OTf (16). The NMR assignment of the observed resonances was consistent
with η2 coordination of the ligand and showed very little shift in the resonance associated with the methyl bound to the palladium center. Therefore, it was determined that the triflate was coordinated to the palladium center, and the solid sate crystal structure confirmed that assessment (Figure 23).78, 233, 272-277
106
Figure 23. ORTEP diagram (50% thermal ellipsoids) of 16. Hydrogen atoms have
been omitted for clarity. Bond lengths (in Å): Pd1-P1 = 2.173(1), Pd1-N1 =
2.188(2), Pd1-O1 = 2.182(2), Pd1-C23 = 2.022(3), N1-C1 = 1.281(4), C1-C2 =
1.461(4), C2-C3 = 1.336(4). Bond angles (in deg): P1-Pd1-N1 = 87.9(1), P1-Pd1-
C23 = 91.3(1), P1-Pd1-O1 = 172.5(1), O1-Pd1-C23 = 86.9(1), O1-Pd1-N1 = 94.3(1).
As shown previously, 3-iminophosphine ligands adopt η1 or η2 coordination
dependent on the coordinative requirements of the palladium center. Clearly, the imine is
a much weaker donor atom than the phosphorus moiety in this type of ligand.
Interestingly, the solid state structure of 15b depends on the recrystallization solvents
used, where two distinct structures were observed. Crystals that yielded a monomeric
solid state structure with an η2-3-iminophosphine ligand were produced from a layered solution of dichloromethane and diethyl ether (Figure 24). This monomeric structure is
completely isomorphous to that observed for 15a, its chloro counterpart. However, when
the solid state structure was obtained from crystals produced from a layered solution of
tetrahydrofuran and pentane, the 3-iminophosphine ligand adopted an η1 coordination
mode, binding to the palladium through the phosphorus atom only, resulting in a dimeric
structure (Figure 25). The NMR spectra for the two sets of crystals were identical,
107 Figure 24. ORTEP diagram (50% thermal ellipsoids) of 15b. Hydrogen atoms have been omitted for clarity. Bond lengths (in Å): Pd1-P1 = 2.208(1), Pd1-N1 =
2.154(4), Pd1-Br1 = 2.530(1), Pd1-C23 = 2.087(6), N1-C1 = 1.275(6), C1-C2 =
1.463(6), C2-C3 = 1.344(7). Bond angles (in deg): P1-Pd1-N1 = 85.8(1), P1-Pd1-
C23 = 93.9(2), Br1-Pd1-N1 = 94.7(1), N1-C1-C2 = 125.2(4), C1-C2-C3 = 125.6(5).
Figure 25. ORTEP diagram (50% thermal ellipsoids) of 15b’. Hydrogen atoms have been omitted for clarity. Bond lengths (in Å): Pd1-P1 = 2.372(1), Pd1-Br1 =
2.584(1), Pd1-Br1a = 2.656(1), Pd1-C23 = 2.031(3), N1-C1 = 1.225(4), C1-C2 =
1.585(4), C2-C3 = 1.304(4). Bond angles (in deg): P1-Pd1-C23 = 94.0(1), P1-Pd1-
Br1 = 88.2(1), P1-Pd1-Br1a = 178.2(1), Br1-Pd1-Br1a = 90.0(1), Br1-Pd1-C23 =
177.7(1), N1-C1-C2 = 127.9(2), C1-C2-C3 = 131.4(2), C2-C3-P1 = 115.1(2). Atoms labeled with an “a” are generated by an inversion symmetry operator: -x, -y+1, -z+1.
108 supporting that the hemilability of the 3-iminophosphine ligand is entirely solvent
dependent. These results represent the first evidence of hemilabile structural isomers in
3-iminophosphine palladium complexes and suggest that a complex solution behavior may be operable. The hemilabile nature of this ligand could play a key role in the catalytic activity displayed by its palladium complexes.
III-3: Experimental Methods
General Considerations. Compounds 8-16 were prepared using standard Schlenk and dry-box techniques. Palladium(II) chloride, palladium(II) bromide, (allyl)palladium(II) chloride dimer, methyllithium complexed with lithium bromide (1.5 M in diethyl ether), and silver triflate were purchased from Strem and used without further purification.
CDCl3 was purchased from Cambridge Isotope Laboratories and for air sensitive applications, was dried over calcium hydride, freeze-pump-thawed three times, vacuum transferred and stored in a nitrogen atmosphere. All other solvents were purchased from
either VWR or Fisher. Pentane, toluene, tetrahydrofuran, and dichloromethane were
purified by passage through a column of activated 4Å molecular sieves and degassed
prior to use. Diethyl ether was purified by passage through a column of activated alumina and degassed prior to use. Acetonitrile was dried over calcium hydride at reflux, distilled and degassed with nitrogen prior to use. Diethylamine, dibenzylamine, morpholine, piperidine, N-methyl-n-butylamine, di-n-butylamine, p-toluidine, cyclohexylamine, tert-butylamine, pyrrolidine, diisopropylamine, benzylamine, and 2,6- diethylaniline used for coordination reactions were purchased from Acros and dried over calcium hydride, freeze-pump-thawed three times, distilled, and stored under nitrogen.
Methyllithium (3.0 M in hexanes) and tetramethyltin were purchased from Aldrich and
109 used without further purification. Lithium bromide was purchased from Fisher and used
without further purification. All 1H and 13C NMR data were obtained on a 600 MHz
Inova NMR spectrometer at ambient temperature at 599.9 and 150.2 MHz, respectively.
31P and 19F NMR data were obtained on a 400 MHz Varian NMR spectrometer at
ambient temperature at 161.9 and 376.3 MHz, respectively. 1H NMR shifts are given
13 relative to CHCl3 (7.26 ppm), and C NMR shifts are given relative to CDCl3 (77.3 ppm). Phosphorus and fluorine NMR were externally referenced to 0.00 ppm with 5%
H3PO4 in D2O and CFCl3, respectively. IR samples were prepared as Nujol mulls and
taken between KBr plates on a Perkin-Elmer XTL FTIR spectrophotometer. Melting
points were observed on a capillary Mel-Temp apparatus in sealed capillary tubes under
nitrogen for compounds 5-12 and are uncorrected. Elemental analyses were determined
by Columbia Analytics, Tucson, AZ and Galbraith Laboratories, Knoxville, TN. Single-
crystal X-ray structure determinations were performed at The University of Toledo.
278, 279 Li[B(C6F5)4] was prepared according to literature.
2 (Ph -Ph-Ph)PdCl2 (8a): 3b (0.379 g, 0.967 mmol) in 20 mL of acetonitrile was added to
a stirring slurry of palladium(II) chloride (0.156 g, 0.879 mmol) in 30 mL of acetonitrile.
The reaction was stirred for an additional 14 h. Solvent was removed, yielding a yellow
solid, which was triturated with pentane (3 x 5 mL) and then washed with diethyl ether to
remove free ligand. The solid was dissolved in methylene chloride and precipitated using pentane at -25°C (0.364 g, 72.8%); mp 230-233°C; 1H NMR (600 MHz) δ 10.38 (dd,
3 3 4 3 JPH = 19.2 Hz, JHH = 9.0 Hz, 1H), 7.82 (dd, JPH = 13.8 Hz, JHH = 9.0 Hz, 1H), 7.74 (d,
3 3 JHH = 7.8 Hz, 2H), 7.67-7.71 (m, 4H), 7.41-7.43 (m, 2H), 7.38 (pseudo t, JHH = 7.8 Hz,
3 3 3 JHH = 7.2 Hz, 2H), 7.31 (t, JHH = 7.8 Hz, 1H), 7.24-7.25 (m, 4H), 7.20 (t, JHH = 7.2 Hz,
110 3 3 13 1 1H), 7.08 (t, JHH = 7.2 Hz, 2H), 6.79 (d, JHH = 7.2 Hz, 2H); C{ H} NMR δ 162.2 (d,
3 1 2 2 JPC = 18.4 Hz), 152.2 (d, JPC = 44.2 Hz), 149.3, 145.2 (d, JPC = 29.4 Hz), 136.0 (d, JPC
3 = 10.8 Hz), 133.6, 131.7, 129.63, 129.56 (d, JPC = 2.6 Hz), 129.0, 128.9, 128.4, 128.3 (d,
2 1 31 1 JPC = 11.7 Hz), 125.9 (d, JPC = 56.0 Hz), 123.5; P{ H} NMR δ 44.5; IR 3045 (w),
2961 (s), 2930 (s), 2898 (s), 2864 (s), 2720 (w), 2668 (w), 1607 (w), 1586 (w), 1481 (m),
1455 (s), 1439 (m), 1376 (m), 1308 (w), 1261 (w), 1203 (w), 1182 (w), 1140 (w), 1093
(m), 1072 (w), 1025 (w), 999 (w), 968 (w), 936 (w), 900 (w), 874 (w), 853 (w), 805 (w),
758 (m), 743 (m), 690 (m), 633 (w), 601 (m), 580 (m), 497 (s); Anal. Calcd for
C27H22Cl2NPPd · 0.1 CH2Cl2: C, 56.38; H, 3.88; N, 2.43. Found: C, 56.20; H, 3.80; N,
2.37.
2 (Ph -Ph-2,6-Me2Ph)PdCl2 (8b): 3c (0.387 g, 0.922 mmol) in 20 mL of acetonitrile was
added to a stirring slurry of palladium(II) chloride (0.149 g, 0.838 mmol) in 30 mL of
acetonitrile. The reaction was stirred for an additional 14 h. Solvent was removed,
yielding a yellow solid, which was triturated with pentane (3 x 5 mL) and then washed
with diethyl ether to remove free ligand. The solid was dissolved in methylene chloride
and precipitated using pentane at -25°C (0.276 g, 55.2%); mp 230-233°C; 1H NMR (600
3 3 4 MHz) δ 10.34 (dd, JPH = 19.8 Hz, JHH = 9.6 Hz, 1H), 7.63-7.66 (m, 4H), 7.60 (dd, JPH =
3 3 13.8 Hz, JHH = 9.6 Hz, 1H), 7.40-7.42 (m, 2H), 7.24-7.27 (m, 4H), 7.16 (t, JHH = 7.2 Hz,
3 3 3 1H), 7.05 (pseudo t, JHH = 7.8 Hz, JHH = 7.2 Hz, 1H), 7.02-7.03 (m, 4H), 6.81 (d, JHH =
13 1 3 1 7.8 Hz, 2H), 2.50 (s, 6H); C{ H} NMR δ 168.3 (d, JPC = 20.8 Hz), 152.3 (d, JPC = 44.0
2 2 Hz), 149.7, 146.1 (d, JPC = 24.3 Hz), 135.9 (d, JPC = 10.5 Hz), 133.9, 131.7, 131.5,
3 2 129.4 (d, JPC = 0.2 Hz), 129.0, 128.9, 128.4, 128.2 (d, JPC = 11.7 Hz), 127.2, 126.7 (d,
1 31 1 JPC = 56.0 Hz), 20.9; P{ H} NMR δ 42.0; IR 2951 (s), 2909 (s), 2857 (s), 2721 (w),
111 2668 (w), 1606 (w), 1565 (w), 1460 (s), 1376 (s), 1313 (w), 1256 (w), 1177 (w), 1146
(w), 1093 (m), 1067 (w), 1025 (w), 999 (w), 931 (w), 889 (w), 853 (w), 821 (w), 769 (m),
743 (m), 722 (m); Anal. Calcd for C29H26Cl2NPPd: C, 58.35; H, 4.40; N, 2.35. Found:
C, 58.05; H, 4.31; N, 2.33.
2 t t (Ph - Bu- Bu)PdCl2 (8c): 3f (0.366 g, 1.04 mmol) in 20 mL of acetonitrile was added to
a stirring slurry of palladium(II) chloride (0.168 g, 0.945 mmol) in 30 mL of acetonitrile.
The reaction was stirred for an additional 14 h. Solvent was removed, yielding a yellow
solid, which was triturated with pentane (3 x 5 mL) and then washed with diethyl ether to
remove free ligand. The solid was dissolved in methylene chloride and precipitated using
pentane at -25°C to yield a yellow solid (0.213 g, 42.6%); mp 218-219°C; 1H NMR (600
3 MHz) δ 7.99-8.02 (m, 2H), 7.80 (d, JHH = 7.2 Hz, 1H), 7.71-7.74 (m, 4H), 7.55 (pseudo
3 3 t, JPH = 8.4 Hz, JHH = 7.2 Hz, 1H), 7.42-7.45 (m, 4H), 1.31 (s, 9H), 1.13 (s, 9H);
13 1 1 2 1 C{ H} NMR δ 161.1 (d, JPC = 16.8 Hz), 137.0 (d, JPC = 15.4 Hz), 133.6 (d, JPC = 12.8
4 2 3 Hz), 132.6 (d, JPC = 3.0 Hz), 130.6 (d, JPC = 13.0 Hz), 129.8 (d, JPC = 4.4 Hz), 128.8 (d,
3 2 3 31 1 JPC = 11.7 Hz), 67.7, 39.9 (d, JPC = 1.8 Hz), 31.7, 30.8 (d, JPC = 2.6 Hz); P{ H} NMR
δ 31.2; IR 3041 (m), 2958 (s), 2916 (s), 2854 (s), 2719 (w), 2667 (w), 1976 (w), 1903
(w), 1820 (w), 1784 (w), 1685 (w), 1612 (w), 1586 (w), 1566 (w), 1462 (s), 1436 (s),
1374 (m), 1311 (w), 1259 (w), 1223 (w), 1197 (m), 1156 (w), 1135 (w), 1088 (m), 1026
(w), 994 (w), 927 (w), 901 (w), 849 (w), 798 (w), 751 (m), 725 (w), 694 (s), 637 (w), 595
(m); Anal. Calcd for C23H30Cl2NPPd: C, 52.23; H, 5.73; N, 2.65. Found: C, 51.97; H,
5.88; N, 2.54.
General Procedure for the Synthesis of (3IP)PdX2 (9a-m): For a half-gram scale
reaction, a slurry of palladium(II) halide (1 equivalent) in 30 mL of acetonitrile and the
112 corresponding 3IP ligand (1.1 equivalents) in 10 mL of methylene chloride were
combined and allowed to stir for 14 h. Solvent was removed, yielding a solid, which was triturated with pentane (5 mL) and then washed with diethyl ether to remove free ligand.
The solid was dissolved in methylene chloride and precipitated using diethyl ether at -
25°C.
2 t 1 (Ph -Pen- Bu)PdCl2 (9a): yellow solid (4.512 g, 90.23%); mp 190°C (dec.); H NMR
4 (600 MHz) δ 7.53-7.58 (m, 6H), 7.48 (d, JPH = 3.0 Hz, 1H), 7.45-7.47 (m, 4H), 2.89-
3 13 1 2.92 (m, 2H), 2.42-2.48 (m, 2H), 2.14 (pent, JHH = 7.8 Hz, 2H), 1.45 (s, 9H); C{ H}
2 1 3 NMR δ 159.9, 156.0 (d, JPC = 16.1 Hz), 135.6 (d, JPC = 44.1 Hz), 133.4 (d, JPC = 11.2
4 2 1 Hz), 132.2 (d, JPC = 5.8 Hz), 128.9 (d, JPC = 12.0 Hz), 125.0 (d, JPC = 57.8 Hz), 67.2,
3 2 3 31 1 36.5 (d, JPC = 2.0 Hz), 36.3 (d, JPC = 11.6 Hz), 31.8, 23.1 (d, JPC = 7.1 Hz); P{ H}
NMR δ 21.5; IR 2252 (w), 1872 (w), 1830 (w), 1794 (w), 1773 (w), 1737 (w), 1700 (m),
1680 (w), 1649 (m), 1618 (w), 1576 (w), 1560 (m), 1534 (w), 1493 (w), 1436 (s), 1389
(m), 1316 (w), 1187 (m), 1166 (m), 1099 (s), 1052 (m), 995 (w), 876 (m), 756 (m), 699
(m). Anal. Calcd for C22H26Cl2NPPd · 2 CH2Cl2: C, 42.23; H, 4.43; N, 2.05. Found: C,
41.69; H, 4.22; N, 2.00.
2 t (Ph -Pen- Bu)PdBr2 (9b): red solid (0.913 g, 91.3%); Alternative Method: Lithium bromide (0.009 g, 0.1 mmol) and 9a (0.017 g, 0.033 mmol) were added to two vials in a
dry box and CDCl3 was added to each and the contents of the vials were mixed.
Quantitative formation of 9b was observed by 1H, 13C and 31P NMR spectroscopy; mp
185°C (dec); 1H NMR (600 MHz) δ 7.53-7.57 (m, 6H), 7.45-7.48 (m, 4H), 7.41 (s, 1H),
3 2.87-2.91 (m, 2H), 2.46-2.52 (m, 2H), 2.14 (pent, JHH = 7.8 Hz, 2H), 1.43 (s, 9H);
13 1 1 3 2 C{ H} NMR δ 163.2 (d, JPC = 73.5 Hz), 159.9 (d, JPC = 9.5 Hz), 156.1 (d, JPC = 15.3
113 3 4 2 Hz), 133.7 (d, JPC = 11.0 Hz), 132.5 (d, JPC = 2.9 Hz), 129.1 (d, JPC = 11.9 Hz), 126.4
1 3 2 (d, JPC = 56.5 Hz), 67.2, 37.1 (d, JPC = 2.6 Hz), 36.6 (d, JPC = 11.6 Hz), 32.2, 23.5 (d,
3 31 1 JPC = 6.4 Hz); P{ H} NMR δ 23.7; IR 2923 (s), 2850 (s), 2722 (w), 2676 (w), 1614
(w), 1578 (w), 1458 (m), 1371 (m), 1307 (w), 1271 (w), 1220 (w), 1183 (w), 1156 (w),
1097 (w), 1028 (w), 1000 (w), 987 (w), 890 (w), 744 (w), 689 (w). Anal. Calcd for
C22H26Br2NPPd · 1.25 CH2Cl2: C, 39.45; H, 4.06; N, 1.98. Found: C, 39.85; H, 4.05; N,
1.90.
2 1 (Ph -Pen-2,6-Me2Ph)PdCl2 (9c): yellow solid (0.309 g, 61.8%); mp 210-213°C; H
3 3 NMR (600 MHz) δ 7.79 (dd, JPH = 12.6 Hz, JHH = 7.2 Hz, 4H), 7.71 (bs, 1H), 7.57 (t,
3 3 3 3 JHH = 7.8 Hz, 2H), 7.48 (pseudo t, JHH = 7.8 Hz, JHH = 7.2 Hz, 4H), 7.06 (t, JHH = 7.2
3 Hz, 1H), 7.01 (d, JHH = 7.2 Hz, 2H), 2.93-2.97 (m, 2H), 2.46-2.50 (m, 2H), 2.22 (s, 6H),
3 3 13 1 3 2.06 (pseudo pent, JHH = 7.8 Hz, JHH = 7.2 Hz, 2H); C{ H} NMR δ 161.8 (d, JPC =
2 1 2 11.0 Hz), 152.4, 152.1 (d, JPC = 17.1 Hz), 136.9 (d, JPC = 37.4 Hz), 133.7 (d, JPC = 11.0
4 3 1 Hz), 132.9 (d, JPC = 3.2 Hz), 130.0, 129.3 (d, JPC = 12.2 Hz), 128.2, 127.3, 127.2 (d, JPC
2 3 31 1 = 63.6 Hz), 38.0 (d, JPC = 11.4 Hz), 36.8, 22.6 (d, JPC = 5.6 Hz), 19.4; P{ H} NMR δ
12.6; IR 3045 (w), 2952 (s), 2920 (s), 2848 (s), 2723 (w), 2671 (w), 1957 (w), 1915 (w),
1760 (w), 1729 (w), 1614 (w), 1573 (w), 1459 (m), 1438 (m), 1376 (w), 1314 (w), 1256
(w), 1185 (w), 1153 (w), 1096 (m), 1064 (w), 1023 (w), 997 (w), 940 (w), 919 (w), 883
(w), 852 (w), 847 (w), 795 (w), 764 (w), 743 (w), 722 (w), 701 (m), 686 (m), 655 (m);
Anal. Calcd for C26H26Cl2NPPd · 0.5 CH2Cl2: C, 52.76; H, 4.52; N, 2.32. Found: C,
52.97; H, 4.59; N, 2.36.
2 1 (Ph -Pen-2,6-Et2Ph)PdCl2 (9d): yellow solid (0.217 g, 43.4%); mp 234-236°C; H
3 3 NMR (600 MHz) δ 7.77 (dd, JPH = 12.6 Hz, JHH = 7.8 Hz, 4H), 7.69 (s, 1H), 7.50 (td,
114 3 5 3 4 JHH = 7.8 Hz, JPH = 6.0 Hz, 2H), 7.47 (td, JHH = 7.8 Hz, JPH = 3.0 Hz, 4H), 7.15 (t,
3 3 2 JHH = 7.2 Hz, 1H), 7.04 (d, JHH = 7.2 Hz, 2H), 2.91-2.94 (m, 2H), 2.74 (dq, JHH = 15.0
3 2 3 Hz, JHH = 7.8 Hz, 2H), 2.46 (dq, JHH = 15.0 Hz, JHH = 7.2 Hz, 2H), 2.43-2.49 (m, 2H),
3 3 3 2.05 (pent, JHH = 7.8 Hz, 2H), 1.08 (pseudo t, JHH = 7.8 Hz, JHH = 7.2 Hz, 6H);
13 1 3 2 1 C{ H} NMR δ 161.7 (d, JPC = 11.0 Hz), 152.0 (d, JPC = 17.2 Hz), 151.1, 137.0 (d, JPC
2 4 3 = 37.0 Hz), 135.5, 133.6 (d, JPC = 11.0 Hz), 132.2 (d, JPC = 3.0 Hz), 129.3 (d, JPC =
1 2 12.0 Hz), 127.6, 127.2 (d, JPC = 63.3 Hz), 125.7, 37.9 (d, JPC = 11.1 Hz), 37.0, 25.6,
3 31 1 22.5 (d, JPC = 5.7 Hz), 14.3; P{ H} NMR δ 12.9; IR 2958 (s), 2916 (s), 2843 (s), 2729
(w), 2677 (w), 1892 (w), 1612 (w), 1587 (w), 1457 (s), 1374 (m), 1332 (w), 1306 (w),
1265 (w), 1182 (w), 1140 (w), 1099 (m), 1073 (w), 1026 (w), 995 (w), 948 (w), 869 (w),
808 (w), 751 (m), 725 (w), 689 (m); Anal. Calcd for C28H30Cl2NPPd: C, 57.11; H, 5.15;
N, 2.38. Found: C, 57.00; H, 5.10; N, 2.40.
2 i (Ph -Pen-2,6- Pr2Ph)PdCl2 (9e): yellow-orange powder (0.362 g, 72.4%); mp 228-
1 3 3 230°C; H NMR (600 MHz) δ 7.78 (dd, JPH = 12.6 Hz, JHH = 8.4 Hz, 4H), 7.71 (s, 1H),
3 3 3 7.59 (t, JHH = 7.2 Hz, 2H), 7.50 (pseudo t, JHH = 8.4 Hz, JHH = 7.2 Hz, 4H), 7.22 (t,
3 3 3 JHH = 7.8 Hz, 1H), 7.10 (d, JHH = 7.8 Hz, 2H), 3.07 (sept, JHH = 6.6 Hz, 2H), 2.93-2.96
3 3 (m, 2H), 2.49-2.51 (m, 2H), 2.10 (pent, JHH = 7.8 Hz, 2H), 1.35 (d, JHH = 6.6 Hz, 6H),
3 13 1 3 2 0.93 (d, JHH = 6.6 Hz, 6H); C{ H} NMR δ 160.9 (d, JPC = 11.0 Hz), 151.8 (d, JPC =
1 2 4 17.4 Hz), 149.5, 140.5, 137.2 (d, JPC = 8.0 Hz), 133.6 (d, JPC = 11.0 Hz), 132.3 (d, JPC
3 1 2 = 2.8 Hz), 129.3 (d, JPC = 12.0 Hz), 128.0, 127.3 (d, JPC = 63.6 Hz), 123.6, 37.9 (d, JPC
3 31 1 = 7.0 Hz), 37.2, 29.2, 24.8, 23.3, 22.5 (d, JPC = 5.7 Hz); P{ H} NMR δ 13.0; IR 3055
(w), 2960 (s), 2919 (s), 2856 (s), 2720 (w), 2667 (w), 2364 (w), 1977 (w), 1670 (w), 1647
(w), 1617 (w), 1584 (w), 1562 (w), 1460 (s), 1434 (m), 1378 (m), 1322 (w), 1251 (w),
115 1210 (w), 1180 (w), 1144 (w), 1098 (m), 1058 (m), 1042 (w), 1027 (w), 996 (w), 966
(w), 925 (w), 884 (w), 844 (w), 803 (w), 747 (m), 691 (m); Anal. Calcd for
C30H34Cl2NPPd · 0.1 CH2Cl2: C, 57.80; H, 5.52; N, 2.24. Found: C, 57.63; H, 5.45; N,
2.22.
2 t 1 (Ph -Pen-4- BuPh)PdCl2 (9f): gray solid (0.176 g, 35.2%); mp 216-217°C; H NMR
3 3 3 (600 MHz) δ 7.73 (dd, JPH = 12.0 Hz, JHH = 7.8 Hz, 4H), 7.70 (bs, 1H), 7.58 (t, JHH =
3 4 3 7.8 Hz, 2H), 7.49 (td, JHH = 7.8 Hz, JPH = 2.4 Hz, 4H), 7.32 (d, JHH = 8.4 Hz, 2H), 7.27
3 3 (d, JHH = 8.4 Hz, 2H), 2.92-2.96 (m, 2H), 2.47-2.49 (m, 2H), 2.10 (pseudo pent, JHH =
3 13 1 3 7.8 Hz, JHH = 7.2 Hz, 2H), 1.28 (s, 9H); C{ H} NMR δ 159.9 (d, JPC = 10.0 Hz),
2 1 2 153.6 (d, JPC = 16.5 Hz), 151.5, 150.6, 136.4 (d, JPC = 40.4 Hz), 133.6 (d, JPC = 11.1
4 3 3 Hz), 132.5 (d, JPC = 3.0 Hz), 129.4 (d, JPC = 12.2 Hz), 126.6 (d, JPC = 61.5 Hz), 125.7,
2 3 31 1 123.0, 37.3 (d, JPC = 11.2 Hz), 37.2 (bs), 34.9, 31.5, 23.1 (d, JPC = 6.2 Hz); P{ H}
NMR δ 16.6; IR 3040 (w), 2954 (s), 2913 (s), 2851 (s), 2726 (w), 1574 (w), 1460 (s),
1372 (s), 1310 (m), 1252 (w), 1185 (w), 1154 (w), 1097 (m), 1019 (w), 993 (w), 915 (w),
801 (w), 764 (m), 744 (m), 718 (m), 687 (m); Anal. Calcd for C28H30Cl2NPPd: C, 57.11;
H, 5.14; N, 2.38. Found: C, 57.22; H, 5.17; N, 2.49.
2 1 (Ph -Pen-CH2Ph)PdCl2 (9g): yellow-orange solid (0.283 g, 56.6%); mp 212-215°C; H
3 3 NMR (600 MHz) δ 7.72 (s, 1H), 7.49 (t, JHH = 7.2 Hz, 2H), 7.43 (dd, JPH = 13.2 Hz,
3 3 3 3 JHH = 7.8 Hz, 4H), 7.35 (pseudo t, JHH = 7.8 Hz, JHH = 7.2 Hz, 4H), 7.31 (d, JHH = 7.8
3 3 3 Hz, 2H), 7.22 (t, JHH = 7.2 Hz, 1H), 7.15 (pseudo t, JHH = 7.8 Hz, JHH = 7.2 Hz, 2H),
3 3 5.78 (s, 2H), 2.88-2.89 (m, 2H), 2.39-2.41 (m, 2H), 2.05 (pseudo pent, JHH = 7.8 Hz, JHH
13 1 3 2 = 7.2 Hz, 2H); C{ H} NMR δ 158.6 (d, JPC = 10.2 Hz), 153.7 (d, JPC = 17.4 Hz),
1 2 4 135.8 (d, JPC = 60.0 Hz), 135.6, 133.4 (d, JPC = 11.0 Hz), 132.1 (d, JPC = 3.0 Hz),
116 3 1 129.9, 129.22, 129.17 (d, JPC = 12.2 Hz), 128.7, 126.7 (d, JPC = 61.8 Hz), 69.9, 37.2 (d,
2 3 3 31 1 JPC = 11.7 Hz), 37.2 (d, JPC = 1.4 Hz), 23.1 (d, JPC = 2.0 Hz); P{ H} NMR δ 17.9; IR
3048 (w), 2955 (s), 2914 (s), 2857 (s), 2727 (w), 2675 (w), 2332 (w), 1990 (w), 1959 (w),
1933 (w), 1818 (w), 1668 (w), 1621 (w), 1590 (w), 1455 (s), 1435 (m), 1378 (m), 1352
(m), 1310 (m), 1263 (w), 1227 (w), 1196 (w), 1160 (m), 1128 (w), 1097 (m), 1045 (m),
1025 (m), 994 (m), 968 (m), 947 (m), 916 (w), 890 (w), 869 (w), 765 (w), 744 (m), 724
(m), 688 (s), 610 (m); Anal. Calcd for C25H24Cl2NPPd: C, 54.91; H, 4.43; N, 2.56.
Found: C, 54.70; H, 4.45; N, 2.74.
2 t (Ph -Hex- Bu)PdCl2 (9h): orange solid (0.244 g, 48.8%); mp 212-214°C; P-N isomer:
1 4 3 H NMR (600 MHz) {CDCl3} δ 7.62 (d, JPH = 3.6 Hz, 1H), 7.56 (t, JHH = 7.2 Hz, 2H),
3 3 7.51-7.54 (m, 4H), 7.46 (pseudo t, JHH = 7.8 Hz, JHH = 7.2 Hz, 4H), 2.49-2.51 (m, 2H),
1.84-1.87 (m, 2H), 1.82-1.84 (m, 2H), 1.69-1.71 (m, 2H), 1.39 (s, 9H); 1H NMR (600
3 3 MHz) {C5D5N} δ 8.19 (dd, JPH = 11.4 Hz, JHH = 7.8 Hz, 4H), 7.38-7.43 (m, 7H), 2.83-
2.85 (m, 2H), 2.18-2.20 (m, 2H), 1.60-1.62 (m, 2H), 1.54-1.58 (m, 2H), 1.32 (s, 9H);
13 1 3 2 C{ H} NMR {C5D5N} δ 157.4 (d, JPC = 20.4 Hz), 146.4 (d, JPC = 3.3 Hz), 136.6 (d,
2 4 1 1 JPC = 10.0 Hz), 131.1 (d, JPC = 2.4 Hz), 130.8 (d, JPC = 56.1 Hz), 129.8 (d, JPC = 56.0
3 3 2 Hz), 128.3 (d, JPC = 11.2 Hz), 55.1, 33.2 (d, JPC = 3.2 Hz), 30.6, 27.4 (d, JPC = 11.7
3 31 1 31 1 Hz), 23.4 (d, JPC = 6.8 Hz), 21.8; P{ H} NMR {CDCl3} δ 29.3; P{ H} NMR
1 4 {C5D5N} δ 23.9; P-alkenyl isomer: H NMR (600 MHz) {C5D5N} δ 10.12 (d, JPH = 3.6
3 3 Hz, 1H), 8.27 (dd, JPH = 10.8 Hz, JHH = 7.8 Hz, 4H), 7.38-7.43 (m, 6H), 5.75-5.79 (m,
1H), 4.81-4.83 (m, 1H), 2.50-2.52 (m, 2H), 2.07-2.11 (m, 2H), 1.69-1.71 (m, 2H), 1.28
31 1 31 1 (s, 9H); P{ H} NMR {CDCl3} δ 37.4; P{ H} NMR {C5D5N} δ 27.3; IR 3050 (w),
2956 (s), 2904 (s), 2852 (s), 2728 (w), 2676 (w), 1959 (w), 1902 (w), 1814 (w), 1772 (w),
117 1632 (w), 1586 (w), 1461 (s), 1435 (m), 1378 (m), 1337 (w), 1311 (w), 1269 (w), 1228
(w), 1181 (w), 1150 (w), 1098 (m), 1072 (w), 1025 (w), 999 (w), 973 (w), 916 (w), 909
(w), 849 (w), 818 (w), 781 (w), 745 (m), 724 (m), 693 (m), 636 (w), 615 (m). Anal.
Calcd for C23H28Cl2NPPd · 1.5 CH2Cl2: C, 44.98; H, 4.79; N, 2.14. Found: C, 45.12; H,
4.73; N, 2.20.
2 1 (Ph -Hex-2,6-Me2Ph)PdCl2 (9i): yellow solid (0.302 g, 60.4%); mp 194-196°C; H
3 3 3 NMR (600 MHz) δ 7.73 (dd, JPH = 11.4 Hz, JHH = 7.8 Hz, 4H), 7.56 (t, JHH = 7.2 Hz,
3 3 3 2H), 7.48 (pseudo t, JHH = 7.8 Hz, JHH = 7.2 Hz, 4H), 7.46 (s, 1H), 7.04 (t, JHH = 7.8
3 Hz, 1H), 6.98 (d, JHH = 7.8 Hz, 2H), 2.56-2.58 (m, 2H), 2.10 (s, 6H), 1.88-1.90 (m, 2H),
13 1 3 1.81-1.84 (m, 2H), 1.70-1.73 (m, 2H); C{ H} NMR δ 165.0 (d, JPC = 15.3 Hz), 151.7,
2 2 4 145.9 (d, JPC = 12.9 Hz), 133.7 (d, JPC = 10.8 Hz), 132.3 (d, JPC = 2.8 Hz), 131.5 (d,
1 3 1 JPC = 37.2 Hz), 130.2, 129.3 (d, JPC = 11.7 Hz), 128.4, 127.4, 126.5 (d, JPC = 59.2 Hz),
2 3 31 1 32.8 (d, JPC = 9.8 Hz), 30.4, 22.5 (d, JPC = 4.2 Hz), 21.6, 19.4; P{ H} NMR δ 30.3; IR
2955 (s), 2904 (s), 2862 (s), 2727 (w), 2664 (w), 1626 (w), 1580 (w), 1455 (s), 1372 (s),
1305 (w), 1258 (w), 1186 (w), 1144 (w), 1113 (m), 1092 (m), 1025 (w), 993 (w), 962
(w), 921 (w), 885 (w), 802 (w), 770 (m), 744 (m), 718 (m), 693 (m), 662 (m); Anal.
Calcd for C27H28Cl2NPPd · 2.5 CH2Cl2: C, 45.01; H, 4.23; N, 1.78. Found: C, 45.13; H,
4.06; N, 1.94.
2 1 (Ph -Hex-2,6-Et2Ph)PdCl2 (9j): red solid (0.297 g, 59.4%); mp 206-208°C; H NMR
3 3 3 (600 MHz) δ 7.74 (dd, JPH = 12.6 Hz, JHH = 7.8 Hz, 4H), 7.56 (t, JHH = 7.2 Hz, 2H),
3 3 3 7.49 (pseudo t, JHH = 7.8 Hz, JHH = 7.2 Hz, 4H), 7.47 (s, 1H), 7.16 (t, JHH = 7.8 Hz,
3 2 3 3 1H), 7.04 (d, JHH = 7.8 Hz, 2H), 2.70 (d pseudo q, JHH = 15.6 Hz, JHH = 7.8 Hz, JHH =
2 3 3 7.2 Hz, 2H), 2.53-2.55 (m, 2H), 2.33 (d pseudo q, JHH = 15.6 Hz, JHH = 7.8 Hz, JHH =
118 7.2 Hz, 2H), 1.90-1.92 (m, 2H), 1.81-1.85 (m, 2H), 1.70-1.74 (m, 2H), 1.26 (pseudo t,
3 3 3 3 JHH = 7.8 Hz, JHH = 7.2 Hz, 3H), 1.01 (pseudo t, JHH = 7.8 Hz, JHH = 7.2 Hz, 3H);
13 1 3 2 C{ H} NMR δ 164.8 (d, JPC = 15.9 Hz), 150.5, 147.8 (d, JPC = 11.2 Hz), 135.7, 133.7
2 4 1 3 (d, JPC = 10.5 Hz), 132.2 (d, JPC = 2.8 Hz), 131.7 (d, JPC = 36.8 Hz), 129.3 (d, JPC =
1 2 11.7 Hz), 127.7, 126.8 (d, JPC = 60.4 Hz), 125.8, 32.9 (d, JPC = 9.9 Hz), 30.6, 25.3, 24.6,
3 31 1 22.5 (d, JPC = 4.5 Hz), 21.7, 14.4, 13.3; P{ H} NMR δ 30.1; IR: 3051 (w), 2958 (s),
2916 (s), 2859 (s), 2729 (w), 1690 (w), 1659 (w), 1618 (w), 1586 (w), 1457 (s), 1436
(m), 1374 (m), 1337 (w), 1306 (m), 1259 (s), 1182 (m), 1093 (s), 1016 (s), 917 (w), 865
(w), 798 (s), 746 (m), 720 (w), 689 (m); Anal. Calcd for C29H32Cl2NPPd · 0.1 CH2Cl2: C,
57.16; H, 5.32; N, 2.29. Found: C, 57.23; H, 5.34; N, 2.37.
2 i (Ph -Hex-2,6- Pr2Ph)PdCl2 (9k): orange-yellow solid (0.357 g, 71.4%); mp 218-220°C;
1 3 3 3 H NMR (600 MHz) δ 7.72 (dd, JPH = 12.0 Hz, JHH = 7.8 Hz, 4H), 7.59 (t, JHH = 7.2
3 3 3 Hz, 2H), 7.51 (s, 1H), 7.49 (pseudo t, JHH = 7.8 Hz, JHH = 7.2 Hz, 4H), 7.20 (t, JHH =
3 3 7.8 Hz, 1H), 7.07 (d, JHH = 7.8 Hz, 2H), 2.94 (sept, JHH = 6.6 Hz, 2H), 2.53-2.55 (m,
3 2H), 1.89-1.91 (m, 2H), 1.82-1.85 (m, 2H), 1.72-1.75 (m, 2H), 1.30 (d, JHH = 6.6 Hz,
3 13 1 3 6H), 0.82 (d, JHH = 6.6 Hz, 6H); C{ H} NMR δ 164.1 (d, JPC = 15.4 Hz), 148.9, 145.8
2 4 1 (bs), 140.8, 133.6 (d, JPC = 10.8 Hz), 132.2 (d, JPC = 2.8 Hz), 131.9 (d, JPC = 36.8 Hz),
3 1 2 129.3 (d, JPC = 11.7 Hz), 128.1, 126.9 (d, JPC = 59.2 Hz), 123.7, 32.9 (d, JPC = 9.9 Hz),
3 31 1 30.7, 29.2, 24.7, 23.5, 22.6 (d, JPC = 4.2 Hz), 21.7; P{ H} NMR δ 30.1; IR 3051 (m),
2958 (s), 2916 (s), 2854 (s), 2729 (w), 2667 (w), 1976 (w), 1913 (w), 1887 (w), 1841 (w),
1799 (w), 1763 (w), 1737 (w), 1669 (w), 1618 (w), 1585 (w), 1570 (w), 1457 (s), 1436
(s), 1374 (w), 1358 (m), 1332 (w), 1311 (w), 1270 (w), 1249 (w), 1182 (m), 1161 (w),
1140 (w), 1124 (w), 1099 (m), 1052 (w), 1026 (w), 1014 (w), 995 (w), 932 (w), 912 (w),
119 886 (w), 802 (m), 766 (w), 751 (m), 720 (m), 694 (m), 667 (m); Anal. Calcd for
C31H36Cl2NPPd · 0.1 CH2Cl2: C, 58.41; H, 5.72; N, 2.19. Found: C, 58.42; H, 5.71; N,
2.19.
2 1 (Ph -Hex-CH2Ph)PdCl2 (9l): yellow solid (0.267 g, 53.4%); 238-241°C; H NMR (600
3 MHz) δ 7.48-7.50 (m, 2H), 7.42 (s, 1H), 7.32-7.37 (m, 8H), 7.16 (t, JHH = 7.2 Hz, 1H),
3 3 7.13 (d, JHH = 7.2 Hz, 2H), 7.05 (t, JHH = 7.2 Hz, 2H), 5.45 (s, 2H), 2.49-2.51 (m, 2H),
13 1 3 1.78-1.81 (m, 4H), 1.65-1.67 (m, 2H); C{ H} NMR δ 161.6 (d, JPC = 15.2 Hz), 146.3
2 2 4 (d, JPC = 12.3 Hz), 135.5, 133.6 (d, JPC = 10.8 Hz), 132.2 (d, JPC = 2.8 Hz), 130.4 (d,
1 3 1 JPC = 42.4 Hz), 129.9, 129.2, 129.1 (d, JPC = 11.7 Hz), 128.7, 125.8 (d, JPC = 58.8 Hz),
2 3 31 1 69.5, 31.5 (d, JPC = 9.9 Hz), 30.5, 22.6 (d, JPC = 5.2 Hz), 21.4; P{ H} NMR δ 34.9;
IR 3058 (w), 3020 (w), 2961 (s), 2922 (s), 2854 (s), 2718 (w), 2669 (w), 1645 (w), 1601
(w), 1582 (w), 1460 (s), 1436 (m), 1378 (m), 1334 (w), 1305 (w), 1261 (w), 1242 (w),
1164 (w), 1116 (m), 1096 (m), 1023 (m), 999 (w), 960 (w), 946 (w), 902 (w), 853 (w),
814 (w), 742 (m), 712 (m), 680 (s); Anal. Calcd for C26H26Cl2NPPd: C, 55.68; H, 4.68;
N, 2.50. Found: C, 55.91; H, 4.83; N, 2.49.
t 2 t 1 ( Bu -Pen- Bu)PdCl2 (9m): red solid (0.344 g, 68.8%), mp 189-191°C; H NMR (600
4 MHz) δ 7.77 (d, JPH = 3.0 Hz, 1H), 2.76-2.80 (m, 1H), 2.64-2.65 (m, 1H), 2.36-2.39 (m,
3 2H), 2.23-2.27 (m, 1H), 2.01-2.03 (m, 1H), 1.67 (s, 9H), 1.56 (d, JPH = 15.6 Hz, 9H),
3 13 1 2 1.41 (d, JPH = 15.6 Hz, 9H); C{ H} NMR δ 175.8 (bs), 147.3 (d, JPC = 17.0 Hz), 126.4
1 2 1 3 (d, JPC = 34.0 Hz), 66.3, 61.1 (d, JPC = 17.0 Hz), 39.2 (d, JPC = 23.4 Hz), 35.6 (d, JPC =
2 3 31 1 8.6 Hz), 32.6, 30.3 (d, JPC = 4.0 Hz), 26.5 (d, JPC = 7.5 Hz); P{ H} NMR δ 37.8; IR
2958 (s), 2916 (s), 2854 (s), 2708 (w), 1649 (w), 1628 (w), 1586 (m), 1462 (s), 1374 (m),
1322 (w), 1270 (w), 1259 (w), 1223 (w), 1171 (m), 1109 (w), 1068 (w), 1010 (m), 984
120 (w), 953 (w), 933 (w), 886 (w), 844 (w), 803 (w), 725 (m), 694 (w), 626 (w), 600 (m);
Anal. Calcd for C18H34Cl2NPPd · 0.5 CH2Cl2: C, 43.12; H, 6.86; N, 2.72. Found: C,
42.79; H, 6.81; N, 2.64.
(Ph2-Pen-tBu)Pd(allyl)Cl (10a): 3p (0.647 g, 1.93 mmol) was dissolved in 10 mL of
methylene chloride and added to (allyl)palldium(II) chloride dimer (0.372 g, 0.965 mmol)
in 10 mL of methylene chloride. The reaction was stirred for 14 h. Volatile materials
were removed in vacuo and the residual solid was triturated with pentane (2 x 5 mL).
The yellow-orange solid was dissolved in 20 mL of diethyl ether and cooled to -25°C
overnight to yield yellow crystals (737 mg, 73.7%); mp 134°C (dec.); 1H NMR (600
3 MHz) δ 8.66 (br s, 1H), 7.69-7.73 (m, 4H), 7.39-7.44 (m, 6H), 5.56 (pent, JHH = 4.2 Hz,
3 1H), 4.71 (m, 1H), 3.69 (m, 1H), 2.99 (m, 2H), 2.92-2.95 (br t, JHH = 7.8 Hz, 2H), 2.40-
3 13 1 3 2.43 (m, 2H), 1.89 (pent, JHH = 7.8 Hz, 2H), 1.05 (s, 9H); C{ H} NMR δ 153.5 (d, JPC
2 1 2 = 2.3 Hz), 152.5 (d, JPC = 10.7 Hz), 137.8 (d, JPC = 32.6 Hz), 134.0 (d, JPC = 12.8 Hz),
1 3 2 132.0 (d, JPC = 42.9 Hz), 130.6, 128.8 (d, JPC = 10.3 Hz), 118.1 (d, JPC = 5.0 Hz), 79.5
3 3 2 (d, JPC = 1.0 Hz), 61.2, 58.1, 39.6 (d, JPC = 5.0 Hz), 35.1 (d, JPC = 9.9 Hz), 29.9, 22.6
3 31 1 (d, JPC = 7.4 Hz); P{ H} NMR δ 7.6; IR 1773 (w), 1747 (w), 1726 (w), 1700 (m), 1680
(w), 1648 (m), 1617 (w), 1576 (w), 1555 (m), 1539 (m), 1519 (w), 1488 (s), 1337 (w),
1306 (w), 1259 (w), 1207 (w), 1181 (w), 1156 (w), 1099 (s), 1041 (s), 969 (w), 860 (m),
829 (m), 767 (w), 741 (m), 694 (s); Anal. Calcd for C25H31ClNPPd: C, 57.93; H, 6.03; N,
2.70. Found: C, 57.88; H, 6.30, N, 2.72.
(tBu2-Pen-tBu)Pd(allyl)Cl (10b): 3aa (0.340 g, 1.15 mmol) was dissolved in 10 mL of
methylene chloride and added to (allyl)palldium(II) chloride dimer (0.191 g, 0.522 mmol)
in 10 mL of methylene chloride. The reaction was stirred for 14 h. Volatile materials
121 were removed in vacuo and the residual solid was triturated with pentane (2 x 5 mL),
resulting in a tan solid (0.213 g, 42.6%), mp 118-120°C; 1H NMR (600 MHz) δ 9.36 (bs,
1H), 5.32-5.39 (m, 1H), 4.60-4.62 (m, 1H), 3.56-3.61 (m, 1H), 2.98-3.02 (m, 4H), 2.77-
3 13 1 2.80 (m, 2H), 1.88-1.92 (m, 2H), 1.42 (d, JPH = 13.8 Hz, 18H), 1.19 (s, 9H); C{ H}
3 2 1 NMR δ 155.8 (d, JPC = 9.6 Hz), 153.9 (d, JPC = 16.5 Hz), 139.8 (d, JPC = 38.6 Hz),
2 3 2 115.6 (d, JPC = 4.8 Hz), 80.3 (d, JPC = 1.0 Hz), 63.0 (d, JPC = 7.0 Hz), 58.1, 41.0 (d,
2 1 2 2 JPC = 1.8 Hz), 38.3 (d, JPC = 38.6 Hz), 33.9 (d, JPC = 9.3 Hz), 30.9 (d, JPC = 75.0 Hz),
3 31 1 30.1, 23.5 (d, JPC = 4.2 Hz); P{ H} NMR δ 54.7; IR 2958 (s), 2916 (s), 2853 (s), 1597
(w), 1451 (m), 1374 (m), 1259 (m), 1223 (w), 1176 (w), 1093 (m), 1021 (m), 938 (w),
896 (w), 865 (w), 803 (s), 725 (w), 658 (w), 606 (w), 580 (m); Anal. Calcd for
C21H39ClNPPd: C, 52.73; H, 8.23; N, 2.93. Found: C, 52.43; H, 8.18; N, 2.97.
[(Ph2-Pen-tBu)Pd(allyl)][OTF] (11a): 10a (0.669 g, 1.27 mmol) was dissolved in 10
mL of methylene chloride and added to a slurry of silver triflate (0.325 g, 1.27 mmol) in
10 mL of methylene chloride and stirred in the absence of light for 2 h. Solvent was
removed in vacuo and the grayish-red solid was triturated with pentane (2 x 5 mL). The
residue was extracted with tetrahydrofuran (3 x 15 mL), leaving behind a gray solid after
filtration. Solvent was removed in vacuo and the product was triturated with 5 mL of
pentane twice to yield an orange-red solid (720 mg, 89.7%); mp 155°C (dec.); 1H NMR
4 (600 MHz) δ 7.94 (d, JPH = 3.0 Hz, 1H), 7.50-7.53 (m, 6H), 7.37-7.42 (m, 4H), 5.69-5.76
3 3 3 (m, 1H), 5.00 (t, JHH = 6.6 Hz, 1H), 3.99 (dd, JPH = 14.4 Hz, JHH = 9.6 Hz, 1H), 3.25 (d,
3 JHH = 4.8 Hz, 1H), 2.97-2.99 (m, 2H), 2.62-2.64 (m, 2H), 2.46-2.49 (m, 1H), 2.04-2.08
13 1 280 3 2 (m, 2H), 1.31 (s, 9H); C{ H} NMR δ 159.7 (d, JPC = 7.9 Hz), 154.9 (d, JPC = 17.3
1 3 1 Hz), 134.3 (d, JPC = 34.2 Hz), 133.0 (d, JPC = 13.6 Hz), 131.8 (d, JPC = 61.5 Hz), 129.6
122 2 3 2 (d, JPC = 17.3 Hz), 129.5, 120.4 (d, JPC = 6.6 Hz), 83.7 (d, JPC = 30.5 Hz), 64.3, 55.8
2 2 3 31 1 (d, JPC = 4.1 Hz), 38.0 (d, JPC = 11.6 Hz), 36.6, 29.7, 22.5 (d, JPC = 6.2 Hz); P{ H}
NMR δ 16.9; 19F{1H} NMR δ -78.5; IR 1794 (w), 1768 (w), 1737 (w), 1716 (w), 1700
(w), 1685 (m), 1654 (m), 1618 (w), 1576 (w), 1560 (m), 1540 (m), 1519 (w), 1493 (m),
1265 (s), 1218 (m), 1187 (w), 1150 (s), 1099 (m), 1031 (s), 876 (w), 824 (w), 803 (w),
751 (w), 704 (w), 637 (w); Anal. Calcd for C26H31F3NO3PPdS: C, 49.41; H, 4.94; N,
2.22. Found: C, 49.56; H, 4.99; N, 2.29.
2 t [(Ph -Pen- Bu)Pd(allyl)][B(C6F5)4] (11b): To a stirring slurry of lithium
tetrakis(pentafluorophenyl)borate (0.354 g, 0.516 mmol) in diethyl ether (20 mL), a
solution of 10a (0.223 g, 0.430 mmol) in diethyl ether (20 mL) was added and stirred for
14 h. Solvent was removed, resulting in a yellow powder, which was washed with pentane (3 x 20 mL), dissolved in diethyl ether and precipitated with pentane (0.234 g,
1 3 46.8%); mp 147-148°C; H NMR (600 MHz) δ 8.02 (s, 1H), 7.54 (t, JHH = 7.8 Hz, 2H),
3 3 3 3 7.47 (pseudo t, JHH = 8.4 Hz, JHH = 7.8 Hz, 4H), 7.41 (dd, JPH = 12.0 Hz, JHH = 8.4
Hz, 4H), 5.57-5.64 (m, 1H), 4.93-4.96 (m, 1H), 3.77-3.81 (m, 1H), 2.82-2.96 (m, 4H),
3 3 2.51-2.55 (m, 2H), 2.01 (pseudo pent, JHH = 7.8 Hz, JHH = 7.2 Hz, 2H), 1.25 (s, 9H);
13 1 3 2 C{ H} NMR δ 154.3 (d, JPC = 15.9 Hz), 151.6 (d, JPC = 9.2 Hz), 149.2 (br s), 147.6
1 1 (br s), 137.3 (br s), 136.1 (d, JPC = 34.0 Hz), 135.7 (br s), 134.0 (d, JPC = 26.2 Hz),
2 3 3 132.9 (d, JPC = 12.2 Hz), 132.2, 129.7 (d, JPC = 11.0 Hz), 120.1 (d, JPC = 6.0 Hz), 83.1
2 2 3 (d, JPC = 27.9 Hz), 66.5, 57.4, 37.6 (d, JPC = 9.9 Hz), 37.3, 29.8, 22.6 (d, JPC = 6.2 Hz);
31 1 19 1 3 P{ H} NMR δ 16.0; F{ H} NMR δ -133.0 (br s, 8F), -163.6 (t, JFF = 18.4 Hz, 4F), -
3 167.2 (br t, JFF = 18.4 Hz, 8F); IR 2955 (s), 2914 (s), 2853 (s), 2731 (w), 2344 (w), 1760
(w), 1638 (w), 1582 (w), 1505 (m), 1454 (s), 1372 (m), 1300 (w), 1259 (w), 1223 (w),
123 1187 (w), 1151 (w), 1084 (m), 1023 (w), 977 (m), 864 (w), 797 (w), 771 (w), 740 (w),
720 (w), 689 (w), 663 (w); Anal. Calcd for C49H31BF20NPPd: C, 50.64; H, 2.69; N, 1.21.
Found: C, 50.97; H, 2.81; N, 1.18.
2 t [(Ph -Pen- Bu)Pd(allyl)][PF6] (11c): To a stirring solution of ammonium
hexafluorophosphate (0.136 g, 0.833 mmol) in dichloromethane (20 mL), 10a (0.360 g,
0.694 mmol) in dichloromethane (20 mL) was added and allowed to stir at ambient
temperature for 14 h. Solvent was removed and the solid was washed with diethyl ether
to remove any unreacted 10a, yielding a mixture of cis and trans isomers in a 10:3 ratio
as a yellow solid (0.436 g, 87.2%); mp 169-174°C; cis isomer: 1H NMR (600 MHz) δ
4 7.88 (d, JPH = 3.6 Hz, 1H), 7.48-7.56 (m, 6H), 7.35-7.43 (m, 4H), 5.67-5.74 (m, 1H),
4.99-5.01 (m, 1H), 3.94-3.98 (m, 1H), 3.25-3.26 (m, 1H), 2.88-3.03 (m, 2H), 2.57-2.64
(m, 2H), 2.44-2.49 (m, 1H), 1.99-2.11 (m, 2H), 1.30 (s, 9H); 13C{1H} NMR δ 159.8 (d,
3 2 1 2 JPC = 7.6 Hz), 155.3 (d, JPC = 17.4 Hz), 134.5 (d, JPC = 34.2 Hz), 133.3 (d, JPC = 13.4
2 4 4 Hz), 132.4 (d, JPC = 12.6 Hz), 132.3 (d, JPC = 2.7 Hz), 131.8 (d, JPC = 2.7 Hz), 129.9
3 3 1 (d, JPC = 11.1 Hz), 129.7 (d, JPC = 11.6 Hz), 128.8 (d, JPC = 49.8 Hz, 2C), 120.7 (d,
2 2 2 2 JPC = 6.3 Hz), 84.0 (d, JPC = 30.0 Hz), 68.3, 56.0 (d, JPC = 3.9 Hz), 38.2 (d, JPC = 11.7
3 31 1 1 Hz), 36.9 (bs), 30.0, 22.8 (d, JPC = 6.0 Hz); P{ H} NMR δ 17.5, -143.2 (sept, JPF =
19 1 1 1 713.4 Hz); F{ H} NMR δ -73.2 (d, JPF = 713.4 Hz); trans isomer: H NMR (600
4 MHz) δ 8.50 (d, JPH = 3.0 Hz, 1H), 7.48-7.56 (m, 6H), 7.35-7.43 (m, 4H), 5.62-5.68 (m,
1H), 5.18-5.21 (m, 1H), 3.83-3.87 (m, 1H), 3.56-3.58 (m, 1H), 2.88-3.03 (m, 2H), 2.57-
2.64 (m, 2H), 2.44-2.49 (m, 1H), 1.99-2.11 (m, 2H), 1.30 (s, 9H); 13C{1H} NMR δ 164.9
3 2 1 2 (d, JPC = 9.2 Hz), 153.6 (d, JPC = 16.2 Hz), 136.3 (d, JPC = 31.6 Hz), 133.2 (d, JPC =
2 4 4 13.2 Hz), 132.6 (d, JPC = 12.6 Hz), 132.3 (d, JPC = 2.7 Hz), 132.0 (d, JPC = 2.7 Hz),
124 3 3 1 129.9 (d, JPC = 10.5 Hz), 129.8 (d, JPC = 10.0 Hz), 128.4 (d, JPC = 47.8 Hz, 2C), 122.7
2 2 2 2 (d, JPC = 5.6 Hz), 81.9 (d, JPC = 27.9 Hz), 68.3, 56.1 (d, JPC = 3.2 Hz), 38.6 (d, JPC =
3 31 1 1 11.4 Hz), 35.8 (bs), 30.0, 22.3 (d, JPC = 5.4 Hz); P{ H} NMR δ 11.0, -143.2 (sept, JPF
19 1 1 = 713.4 Hz); F{ H} NMR δ -73.2 (d, JPF = 713.4 Hz); IR 3319 (w), 2962 (s), 2927 (s),
2847 (s), 2731 (w), 2678 (w), 1619 (w), 1579 (w), 1437 (m), 1403 (m), 1374 (w), 1307
(w), 1259 (w), 1192 (w), 1152 (w), 1094 (w), 1076 (w), 1023 (w), 996 (w), 974 (w), 921
(w), 836 (s), 801 (w), 743 (w), 721 (w), 694 (w), 552 (s); Anal. Calcd for
C25H31F6NP2Pd: C, 47.82; H, 4.98; N, 2.23. Found: C, 48.29; H, 5.07; N, 2.33.
2 t (Ph -Pen- Bu)PdCl2(HN(C2H6)2) (12a): To a stirring solution of 9a (0.438 g, 0.853
mmol) in dichloromethane (25 mL), diethylamine (0.062 g, 0.85 mmol) in
dichloromethane (10 mL) was added and allowed to stir at ambient temperature for 4 h.
Solvent was removed and the solid was triturated with diethyl ether. The red solid was
recrystallized from diethyl ether at -25°C (0.321 g, 64.2%); mp 124-126°C; 1H NMR281
(600 MHz) δ 8.50 (s, 1H), 7.80-7.81 (m, 4H), 7.42-7.45 (m, 2H), 7.37-7.40 (m, 4H),
3 3 3.15-3.17 (m, 2H), 2.88-2.91 (m, 2H), 2.60 (q, JHH = 6.6 Hz, 4H), 2.09 (pent, JHH = 7.2
3 13 1 2 Hz, 2H), 1.54 (t, JHH = 6.6 Hz, 6H), 1.03 (s, 9H); C{ H} NMR δ 153.5 (d, JPC = 4.9
3 1 3 Hz), 153.4 (d, JPC = 8.6 Hz), 136.4 (d, JPC = 45.7 Hz), 135.0 (d, JPC = 10.8 Hz), 131.1
4 1 2 3 (d, JPC = 2.9 Hz), 129.8 (d, JPC = 56.4 Hz), 128.4 (d, JPC = 11.2 Hz), 58.3, 46.9 (d, JPC
3 2 3 = 2.8 Hz), 40.8 (d, JPC = 6.6 Hz), 35.0 (d, JPC = 12.1 Hz), 29.8, 22.9 (d, JPC = 8.6 Hz),
15.6; 31P{1H} NMR δ 15.6; IR 3236 (w), 2957 (s), 2920 (s), 2847 (s), 2728 (w), 2673
(w), 1617 (w), 1576 (w), 1457 (m), 1374 (m), 1306 (w), 1260 (w), 1181 (w), 1150 (w),
1090 (w), 1068 (w), 1022 (w), 948 (w), 893 (w), 825 (w), 802 (w), 742 (w), 719 (w), 692
125 (w); Anal. Calcd for C26H37Cl2N2PPd: C, 53.30; H, 6.37; N, 4.78. Found: C, 53.52; H,
6.48; N, 4.56.
General Procedure for NMR Scale Imine Displacement Reactions: In a drybox, a solution of amine (0.039 mmol) in 0.6 mL of CDCl3 was added to a vial containing 9a
(0.020 g, 0.039 mmol). The solutions were allowed to stand for 10 min before the spectra
were obtained.
2 t 1 (Ph -Pen- Bu)PdCl2(HN(C2H4)2O) (12b): H NMR (600 MHz) δ 8.89 (s, 1H), 7.72-
3 7.76 (m, 4H), 7.44-7.46 (m, 2H), 7.36-7.39 (m, 4H), 3.86 (d, JHH = 10.8 Hz, 4H), 3.33
3 3 (d, JPH = 7.2 Hz, 1H), 3.01 (d, JHH = 10.8 Hz, 4H), 2.90-2.93 (m, 2H), 2.52-2.55 (m,
3 3 13 1 2H), 1.90 (pseudo pent, JHH = 7.8 Hz, JHH = 7.2 Hz, 2H), 1.10 (s, 9H); C{ H} NMR δ
2 3 1 3 154.1 (d, JPC = 6.9 Hz), 153.5 (d, JPC = 9.4 Hz), 136.1 (d, JPC = 46.8 Hz), 135.1 (d, JPC
4 1 2 = 10.6 Hz), 131.3 (d, JPC = 2.8 Hz), 129.2 (d, JPC = 57.2 Hz), 128.3 (d, JPC = 11.4 Hz),
4 3 3 2 68.2 (d, JHH = 3.2 Hz), 58.4, 48.2 (d, JPC = 3.2 Hz), 40.6 (d, JPC = 5.8 Hz), 35.0 (d, JPC
3 31 1 = 12.3 Hz), 30.1, 22.8 (d, JPC = 8.7 Hz); P{ H} NMR δ 16.7.
2 t 1 (Ph -Pen- Bu)PdCl2(HN(C5H10)) (12c): H NMR (600 MHz) δ 8.90 (s, 1H), 7.72-7.76
(m, 4H), 7.42-7.45 (m, 2H), 7.35-7.38 (m, 4H), 3.22-3.24 (m, 2H), 3.12-3.16 (m, 2H),
3 3.04-3.10 (m, 1H), 2.89-2.92 (m, 2H), 2.50-2.54 (m, 2H), 1.89 (pseudo pent, JHH = 7.8
3 13 1 Hz, JHH = 7.2 Hz, 2H), 1.68-1.74 (m, 3H), 1.50-1.55 (m, 3H), 1.11 (s, 9H); C{ H}
2 3 1 NMR δ 153.8 (d, JPC = 7.2 Hz), 153.6 (d, JPC = 9.4 Hz), 136.3 (d, JPC = 45.9 Hz), 135.1
2 4 1 3 (d, JPC = 10.5 Hz), 131.1 (d, JPC = 3.0 Hz), 129.4 (d, JPC = 56.0 Hz), 128.2 (d, JPC =
3 3 2 11.2 Hz), 58.3, 49.3 (d, JPC = 3.4 Hz), 40.6 (d, JPC = 5.7 Hz), 35.0 (d, JPC = 12.0 Hz),
4 3 31 1 30.0, 27.4 (d, JPC = 3.4 Hz), 24.0, 22.8 (d, JPC = 8.6 Hz); P{ H} NMR δ 16.2.
126 2 t n 1 (Ph -Pen- Bu)PdCl2(HN(Me) Bu) (12d): H NMR (600 MHz) δ 8.74 (s, 1H), 7.76-7.79
(m, 4H), 7.43-7.46 (m, 2H), 7.37-7.40 (m, 4H), 3.27-3.32 (m, 1H), 3.13-3.20 (m, 1H),
3 3 2.89-2.92 (m, 2H), 2.64 (dd, JHH = 6.6 Hz, JPH = 4.2 Hz, 3H), 2.52-2.56 (m, 2H), 2.38-
3 3 2.45 (m, 1H), 2.04-2.10 (m, 1H), 1.90 (pseudo pent, JHH = 7.8 Hz, JHH = 7.2 Hz, 2H),
3 1.79-1.86 (m, 1H), 1.44-1.50 (m, 1H), 1.37-1.42 (m, 1H), 1.08 (s, 9H), 0.97 (t, JHH = 7.2
13 1 2 3 1 Hz, 3H); C{ H} NMR δ 153.7 (d, JPC = 6.9 Hz), 153.6 (d, JPC = 9.2 Hz), 136.3 (d, JPC
2 4 1 = 45.9 Hz), 135.1 (d, JPC = 10.5 Hz), 131.2 (d, JPC = 2.7 Hz), 129.6 (d, JPC = 56.0 Hz),
3 3 3 128.5 (d, JPC = 11.4 Hz), 58.3, 53.4 (d, JPC = 2.8 Hz), 40.6 (d, JPC = 6.0 Hz), 39.1 (d,
3 2 3 JPC = 3.6 Hz), 36.0 (d, JPC = 12.2 Hz), 31.7, 30.0, 22.8 (d, JPC = 8.6 Hz), 20.5, 14.3;
31P{1H} NMR δ 16.0.
2 t n 1 (Ph -Pen- Bu)PdCl2(HN Bu2) (12e): H NMR (600 MHz) δ 8.43 (s, 1H), 7.80-7.84 (m,
4H), 7.42-7.46 (m, 2H), 7.37-7.40 (m, 4H), 3.26-3.31 (m, 1H), 3.10-3.17 (m, 2H), 2.86-
2.89 (m, 2H), 2.55-2.58 (m, 2H), 2.46-2.53 (m, 2H), 2.14-2.22 (m, 2H), 1.90 (pseudo
3 3 pent, JHH = 7.8 Hz, JHH = 7.2 Hz, 2H), 1.82-1.88 (m, 2H), 1.43-1.51 (m, 2H), 1.34-1.41
3 13 1 3 (m, 2H), 1.02 (s, 9H), 0.97 (t, JHH = 7.2 Hz, 6H); C{ H} NMR δ 153.5 (d, JPC = 8.6
2 1 2 Hz), 153.4 (d, JPC = 6.2 Hz), 136.4 (d, JPC = 45.4 Hz), 135.0 (d, JPC = 10.8 Hz), 131.1
4 1 3 3 (d, JPC = 2.8 Hz), 129.8 (d, JPC = 55.8 Hz), 128.4 (d, JPC = 11.1 Hz), 58.2, 52.3 (d, JPC
3 2 3 = 3.0 Hz), 40.7 (d, JPC = 6.9 Hz), 34.9 (d, JPC = 12.2 Hz), 32.2, 29.8, 22.8 (d, JPC = 8.6
Hz), 20.6, 14.3; 31P{1H} NMR δ 15.8.
2 t 1 (Ph -Pen- Bu)PdCl2(HN(CH2C6H5)2) (12f): H NMR (600 MHz) δ 8.22 (s, 1H), 7.52-
7.58 (m, 8H), 7.39-7.43 (m, 8H), 7.30-7.33 (m, 4H), 4.36-4.41 (m, 2H), 3.86-3.94 (m,
3 1H), 3.76-3.80 (m, 2H), 2.84-2.87 (m, 2H), 2.42-2.45 (m, 2H), 1.86 (pseudo t, JHH = 7.8
3 13 1 3 Hz, JHH = 7.2 Hz, 2H), 0.98 (s, 9H); C{ H} NMR δ 153.8 (d, JPC = 8.1 Hz), 153.4 (d,
127 2 1 2 4 JPC = 5.2 Hz), 136.4, 135.7 (d, JPC = 46.2 Hz), 135.1 (d, JPC = 11.0 Hz), 131.1 (d, JPC
1 3 = 2.7 Hz), 130.3, 129.7 (d, JPC = 56.6 Hz), 129.1, 128.4, 128.3 (d, JPC = 11.2 Hz), 58.1,
3 3 2 54.7 (d, JPC = 2.7 Hz), 40.4 (d, JPC = 7.8 Hz), 35.0 (d, JPC = 12.2 Hz), 29.8, 22.7 (d,
3 31 1 JPC = 8.7 Hz); P{ H} NMR δ 17.2.
2 t 1 (Ph -Pen- Bu)PdCl2(HN(C4H8)) (12g): H NMR (600 MHz) δ 9.08 (s, 1H), 7.72-7.76
(m, 4H), 7.42-7.45 (m, 2H), 7.36-7.38 (m, 4H), 3.34-3.37 (m, 1H), 3.14-3.17 (m, 4H),
3 3 2.90-2.93 (m, 2H), 2.49-2.52 (m, 2H), 1.89 (pseudo pent, JHH = 7.8 Hz, JHH = 7.2 Hz,
13 1 3 2H), 1.83-1.88 (m, 2H), 1.62-1.64 (m, 2H), 1.14 (s, 9H); C{ H} NMR δ 153.9 (d, JPC =
2 1 2 7.0 Hz), 153.7 (d, JPC = 9.6 Hz), 136.3 (d, JPC = 46.0 Hz), 135.2 (d, JPC = 10.5 Hz),
4 1 3 131.2 (d, JPC = 2.8 Hz), 129.3 (d, JPC = 56.2 Hz), 128.2 (d, JPC = 11.2 Hz), 58.4, 49.1
3 3 2 4 (d, JPC = 2.2 Hz), 40.5 (d, JPC = 5.2 Hz), 35.0 (d, JPC = 12.0 Hz), 30.1, 24.6 (d, JPC =
3 31 1 4.2 Hz), 22.8 (d, JPC = 8.2 Hz); P{ H} NMR δ 15.7.
2 t i 1 (Ph -Pen- Bu)PdCl2(HN Pr2) (12h): H NMR (600 MHz) δ 8.36 (s, 1H), 7.77-7.81 (m,
4H), 7.41-7.43 (m, 2H), 7.35-7.38 (m, 4H), 3.28-3.34 (m, 2H), 3.23-3.27 (m, 1H), 2.84-
3 3 2.88 (m, 2H), 2.57-2.60 (m, 2H), 1.88 (pseudo pent, JHH = 7.8 Hz, JHH = 7.2 Hz, 2H),
3 3 13 1 1.58 (d, JHH = 6.0 Hz, 6H), 1.40 (d, JHH = 6.6 Hz, 6H), 0.99 (s, 9H); C{ H} NMR δ
2 3 1 2 153.4 (d, JPC = 8.4 Hz), 153.1 (d, JPC = 5.8 Hz), 136.6 (d, JPC = 46.0 Hz), 135.0 (d, JPC
4 1 3 = 10.6 Hz), 131.0 (d, JPC = 2.7 Hz), 130.0 (d, JPC = 56.1 Hz), 128.3 (d, JPC = 11.2 Hz),
3 3 2 58.1, 49.2 (d, JPC = 2.7 Hz), 41.0 (d, JPC = 5.2 Hz), 34.9 (d, JPC = 12.2 Hz), 29.7, 23.6
4 3 31 1 (bs), 23.4 (d, JPC = 2.7 Hz), 22.8 (d, JPC = 8.8 Hz); P{ H} NMR δ 15.4.
2 t 1 (Ph -Pen- Bu)PdCl2(H2NCy) (12i): H NMR (600 MHz) δ 8.78 (s, 1H), 7.76-7.80 (m,
4H), 7.43-7.46 (m, 2H), 7.37-7.40 (m, 4H), 3.06-3.11 (m, 1H), 2.89-2.92 (m, 2H), 2.66
3 3 (pseudo t, JHH = 6.6 Hz, JPH = 6.0 Hz, 2H), 2.53-2.56 (m, 2H), 2.26-2.28 (m, 2H), 1.90
128 3 3 (pseudo pent, JHH = 7.8 Hz, JHH = 7.2 Hz, 2H), 1.74-1.78 (m, 2H), 1.60-1.63 (m, 1H),
1.29-1.34 (m, 2H), 1.21-1.27 (m, 2H), 1.10-1.15 (m, 1H), 1.08 (s, 9H); 13C{1H} NMR δ
2 3 1 2 153.9 (d, JPC = 6.8 Hz), 153.5 (d, JPC = 9.2 Hz), 136.0 (d, JPC = 46.2 Hz), 135.1 (d, JPC
4 1 3 = 10.6 Hz), 131.2 (d, JPC = 2.8 Hz), 129.4 (d, JPC = 56.6 Hz), 128.4 (d, JPC = 11.4 Hz),
3 3 4 2 58.3, 52.8 (d, JPC = 2.2 Hz), 40.6 (d, JPC = 6.2 Hz), 36.1 (d, JPC = 2.4 Hz), 35.0 (d, JPC
3 31 1 = 12.3 Hz), 29.9, 25.5, 25.2, 22.7 (d, JPC = 8.4 Hz); P{ H} NMR δ 15.5.
2 t t 1 (Ph -Pen- Bu)PdCl2(H2N Bu) (12j): H NMR (600 MHz) δ 8.67 (s, 1H), 7.78-7.82 (m,
3 4H), 7.43-7.44 (m, 2H), 7.37-7.40 (m, 4H), 2.87-2.90 (m, 2H), 2.86 (d, JPH = 6.0 Hz,
3 3 2H), 2.55-2.58 (m, 2H), 1.89 (pseudo pent, JHH = 7.8 Hz, JHH = 7.2 Hz, 2H), 1.45 (s,
13 1 2 3 9H), 1.05 (s, 9H); C{ H} NMR δ 153.8 (d, JPC = 6.6 Hz), 153.5 (d, JPC = 8.8 Hz),
1 2 4 136.0 (d, JPC = 47.1 Hz), 135.1 (d, JPC = 10.5 Hz), 131.2 (d, JPC = 2.8 Hz), 129.5 (d,
1 3 3 3 JPC = 57.0 Hz), 128.4 (d, JPC = 11.2 Hz), 58.3, 53.7 (d, JPC = 1.4 Hz), 40.7 (d, JPC =
2 4 3 6.4 Hz), 35.0 (d, JPC = 12.2 Hz), 32.5 (d, JPC = 2.2 Hz), 29.9, 22.8 (d, JPC = 8.6 Hz);
31P{1H} NMR δ 15.8.
2 t 1 (Ph -Pen- Bu)PdCl2(H2N-p-CH3C6H4) (12k): H NMR (600 MHz) δ 8.68 (s, 1H), 7.79-
3 7.82 (m, 4H), 7.43-7.44 (m, 2H), 7.37-7.40 (m, 4H), 7.21 (d, JHH = 7.8 Hz, 2H), 7.01 (d,
3 JHH = 7.8 Hz, 2H), 2.94-2.96 (m, 2H), 2.88-2.90 (m, 2H), 2.55-2.58 (m, 2H), 2.31 (s,
3 3 13 1 3H), 1.89 (pseudo pent, JHH = 7.8 Hz, JHH = 7.2 Hz, 2H), 1.06 (s, 9H); C{ H} NMR δ
2 3 2 153.6 (d, JPC = 8.6 Hz), 153.5 (d, JPC = 5.8 Hz), 143.9, 135.1 (d, JPC = 10.5 Hz), 135.0
1 4 3 (d, JPC = 47.2 Hz), 131.2 (d, JPC = 2.8 Hz), 129.2, 129.1, 128.6 (d, JPC = 11.4 Hz),
1 3 2 125.3 (d, JPC = 57.4 Hz), 123.1, 58.3, 40.7 (d, JPC = 6.4 Hz), 36.6 (d, JPC = 11.6 Hz),
3 31 1 32.5, 29.9, 22.8 (d, JPC = 8.6 Hz); P{ H} NMR δ 17.3.
129 2 t 1 (Ph -Pen- Bu)PdCl2(H2NCH2C6H5) (12l): H NMR (600 MHz) δ 8.87 (s, 1H), 7.76-
7.80 (m, 4H), 7.45-7.48 (m, 2H), 7.38-7.41 (m, 4H), 7.36-7.38 (m, 2H), 7.33-7.35 (m,
3H), 4.10-4.13 (m, 2H), 2.95-2.98 (m, 2H), 2.91-2.94 (m, 2H), 2.54-2.56 (m, 2H), 1.91
3 3 13 1 (pseudo pent, JHH = 7.8 Hz, JHH = 7.2 Hz, 2H), 1.10 (s, 9H); C{ H} NMR δ 154.2 (d,
3 2 4 1 JPC = 6.8 Hz), 153.6 (d, JPC = 9.0 Hz), 139.1 (d, JPC = 3.4 Hz), 135.7 (d, JPC = 47.0
2 4 1 Hz), 135.1 (d, JPC = 10.8 Hz), 131.3 (d, JPC = 2.8 Hz), 129.4, 129.1 (d, JPC = 57.2 Hz),
3 3 3 128.5, 128.45, 128.39 (d, JPC = 11.4 Hz), 58.5, 48.1 (d, JPC = 2.6 Hz), 40.4 (d, JPC = 6.3
2 3 31 1 Hz), 35.1 (d, JPC = 12.3 Hz), 30.0, 22.8 (d, JPC = 8.6 Hz); P{ H} NMR δ 16.4.
2 t [(Ph -Pen- Bu)Pd(Cl)]2[OTf]2 (13a): To a stirring slurry of silver triflate (0.410 g, 1.60 mmol) in dichloromethane (20 mL), 9a (0.819 g, 1.60 mmol) in dichloromethane (20 mL) was added and stirred at ambient temperature for 14 h in the absence of light.
Solvent was removed and the orange solid was dissolved in THF and precipitated with
1 4 pentane at -25°C (0.621 g, 62.1%); mp 156-158°C; H NMR (600 MHz) δ 10.36 (d, JPH
= 16.8 Hz, 1H), 7.64-7.69 (m, 6H), 7.56-7.59 (m, 4H), 3.19-3.22 (m, 2H), 2.63-2.66 (m,
3 13 1 280 1 2H), 2.13 (pent, JHH = 7.8 Hz, 2H), 1.61 (s, 9H); C{ H} NMR δ 163.4 (d, JPC =
3 2 4 81.8 Hz), 161.6 (d, JPC = 2.0 Hz), 150.0 (d, JPC = 5.0 Hz), 133.7 (d, JPC = 2.8 Hz),
3 2 1 132.0 (d, JPC = 10.5 Hz), 129.6 (d, JPC = 12.6 Hz), 129.6 (d, JPC = 107.4 Hz), 63.0, 39.8
3 2 3 31 1 (d, JPC = 9.6 Hz), 34.0 (d, JPC = 10.6 Hz), 28.2, 23.5 (d, JPC = 8.8 Hz); P{ H} NMR δ
27.5; 19F{1H} NMR δ -78.7; IR 3152 (w), 2960 (s), 2923 (s), 2850 (s), 2731 (w), 1651
(w), 1586 (w), 1458 (m), 1375 (m), 1288 (m), 1261 (m), 1224 (w), 1188 (w), 1151 (w),
1114 (w), 1096 (w), 1064 (w), 1032 (m), 958 (w), 798 (w), 752 (w), 720 (w), 697 (w),
282 633 (m); Anal. Calcd. for C44H52Cl2N2P2Pd2: C, 55.35; H, 5.50; N, 2.93. Found: C,
55.31; H, 5.20; N, 2.82.
130 2 t [(Ph -Pen- Bu)Pd(Br)]2[OTf]2 (13b): To a stirring slurry of silver triflate (0.192 g,
0.745 mmol) in dichloromethane (20 mL), 9b (0.448 g, 0.745 mmol) in dichloromethane
(20 mL) was added and stirred at ambient temperature for 14 h in the absence of light.
Solvent was removed and the orange solid was dissolved in THF and precipitated with
1 4 pentane at -25°C (0.273 g, 54.6%); mp 159-160°C; H NMR (600 MHz) δ 10.35 (d, JPH
= 17.4 Hz, 1H), 7.64-7.68 (m, 6H), 7.56-7.59 (m, 4H), 3.18-3.21 (m, 2H), 2.64-2.67 (m,
3 3 13 1 280 2H), 2.12 (pseudo pent, JHH = 7.8 Hz, JHH = 7.2 Hz, 2H), 1.61 (s, 9H); C{ H} NMR
1 2 4 δ 163.5 (d, JPC = 56.1 Hz), 161.6, 150.1 (d, JPC = 15.4 Hz), 133.7 (d, JPC = 2.7 Hz),
3 2 1 133.0 (d, JPC = 10.5 Hz), 129.6 (d, JPC = 12.4 Hz), 129.4 (d, JPC = 60.3 Hz), 63.0, 39.8
3 2 3 31 1 (d, JPC = 9.8 Hz), 34.0 (d, JPC = 11.0 Hz), 28.2, 23.5 (d, JPC = 8.7 Hz); P{ H} NMR δ
27.9; 19F{1H} NMR δ -78.7; IR 3155 (w), 3120 (w), 3041 (w), 2916 (s), 2854 (s), 2729
(w), 1649 (m), 1586 (w), 1457 (m), 1436 (m), 1400 (w), 1379 (m), 1332 (w), 1285 (m),
1259 (m), 1223 (m), 1192 (m), 1156 (m), 1114 (m), 1099 (w), 1062 (w), 1031 (m), 995
(w), 953 (w), 901 (w), 824 (w), 792 (w), 751 (m), 720 (m), 694 (m), 632 (m); Anal.
282 Calcd. for C44H52Br2N2P2Pd2: C, 50.65; H, 5.02; N, 2.68. Found: C, 50.78; H, 5.12;
N, 2.55.
2 t (Ph -Pen- Bu)Pd(OTf)2 (14): Method A: To a stirring slurry of silver triflate (0.365 g,
1.42 mmol) in dichloromethane (20 mL), 9a (0.346 g, 0.676 mmol) in dichloromethane
(20 mL) was added and stirred at ambient temperature for 14 h in the absence of light.
Solvent was removed and the orange solid was dissolved in tetrahydrofuran and precipitated with pentane at -25°C (0.287 g, 57.4%); Method B: To a stirring slurry of
silver triflate (0.038 g, 0.15 mmol) in dichloromethane (10 mL), 13a (0.085 g, 0.14
mmol) in dichloromethane (10 mL) was added and stirred at ambient temperature for 14
131 h in the absence of light. Solvent was removed and the orange solid was dissolved in
tetrahydrofuran and precipitated with pentane at -25°C (0.073 g, 73%); mp 160-161°C;
1H NMR (600 MHz) δ 7.68-7.70 (m, 6H), 7.56-7.59 (m, 4H), 7.23 (bs, 1H), 3.02-3.05 (m,
3 13 1 2H), 2.69-2.72 (m, 2H), 2.31 (pent, JHH = 7.8 Hz, 2H), 1.45 (s, 9H); C{ H} NMR δ
2 1 3 164.1 (d, JPC = 14.4 Hz), 160.9 (d, JPC = 62.4 Hz), 159.6 (d, JPC = 9.4 Hz), 134.1 (bs),
3 2 1 133.6 (d, JPC = 9.0 Hz), 130.1 (d, JPC = 13.2 Hz), 121.4 (d, JPC = 65.1 Hz), 53.7, 39.8
2 3 31 1 (d, JPC = 10.5 Hz), 36.1 (bs), 31.0, 23.8 (d, JPC = 9.2 Hz); P{ H} NMR δ 22.3;
19F{1H} NMR δ -77.8; IR 3051 (w), 2958 (s), 2916 (s), 2843 (s), 1618 (w), 1581 (w),
1457 (m), 1435 (m), 1389 (w), 1368 (m), 1301 (s), 1228 (s), 1207 (s), 1166 (s), 1099 (m),
1068 (w), 1021 (s), 964 (w), 891 (w), 751 (m), 694 (m), 632 (m); Anal. Calcd for
C24H26F6NO6PPdS2: C, 38.96; H, 3.54; N, 1.89. Found: C, 38.93; H, 3.01; N, 1.81.
2 t (Ph -Pen- Bu)Pd(CH3)Cl (15a). Method A: To a stirring solution of 9a (0.521 g, 1.02
mmol) in THF (40 mL) at 0°C, methyllithium (0.37 mL, 1.1 mmol) was added via
syringe. The reaction was warmed to ambient temperature over 14 h. Solvent was
removed and the yellow solid was washed with diethyl ether. The solid was dissolved in
dichloromethane and precipitated with diethyl ether (0.241 g, 48.2%); Method B: To a stirring solution of 9a (0.521 g, 1.02 mmol) in dichloromethane (40 mL), tetramethyltin
(0.28 mL, 2.03 mmol) was added via syringe. The reaction was stirred at ambient temperature for 40 h. Solvent was removed and the yellow solid was washed with pentane (3 x 30 mL) to remove any leftover tetramethyltin. The solid was dissolved in dichloromethane and precipitated with diethyl ether (0.363 g, 72.6%); mp 139-141°C; 1H
4 NMR (600 MHz) δ 7.70 (d, JPH = 3.0 Hz, 1H), 7.47-7.50 (m, 2H), 7.39-7.44 (m, 8H),
3 2.75-2.79 (m, 2H), 2.40-2.44 (m, 2H), 2.01 (pent, JHH = 7.8 Hz, 2H), 1.43 (s, 9H), 0.64
132 3 13 1 3 2 (d, JPH = 3.0 Hz, 3H); C{ H} NMR δ 157.5 (d, JPC = 6.0 Hz), 152.2 (d, JPC = 15.2
1 2 4 Hz), 135.8 (d, JPC = 38.8 Hz), 133.5 (d, JPC = 12.0 Hz), 131.3 (d, JPC = 2.6 Hz), 129.0
3 1 3 2 (d, JPC = 11.0 Hz), 128.9 (d, JPC = 51.0 Hz), 63.6, 38.1 (d, JPC = 1.8 Hz), 37.3 (d, JPC =
3 2 31 1 11.3 Hz), 31.3, 23.2 (d, JPC = 6.0 Hz), 3.6 (d, JPC = 0.4 Hz); P{ H} NMR δ 28.2; IR
3051 (w), 2926 (s), 2852 (s), 2724 (w), 2678 (w), 1620 (w), 1574 (w), 1460 (m), 1437
(m), 1377 (m), 1308 (w), 1231 (w), 1198 (w), 1157 (w), 1098 (w), 1070 (w), 1024 (w),
1000 (w), 992 (w), 942 (w), 892 (w), 791 (w), 759 (w), 735 (w), 717 (w), 690 (m); Anal.
Calcd for C23H29ClNPPd: C, 56.11; H, 5.94; N, 2.84. Found: C, 56.13; H, 5.62; N, 2.78.
2 t (Ph -Pen- Bu)Pd(CH3)Br (15b): Method A: To a stirring solution of 9a (0.478 g,
0.931 mmol) in tetrahydrofuran (40 mL) at 0°C, methyllithium complexed with lithium bromide (0.68 mL, 1.0 mmol) was added slowly via syringe. The reaction was allowed to warm to ambient temperature over the course of 1 h. Solvent was removed to afford a red-orange powder. The powder was dissolved in dichloromethane and precipitated with diethyl ether (0.278 g, 55.6%); Method B: To a stirring solution of 9b (0.560 g, 0.931
mmol) in dichloromethane (40 mL), tetramethyltin (0.27 mL, 1.96 mmol) was added via
syringe. The reaction was stirred at ambient temperature for 40 h. Solvent was removed
and the yellow solid was washed with pentane (3 x 30 mL) to remove any leftover
tetramethyltin. The solid was dissolved in dichloromethane and precipitated with diethyl
ether (0.381 g, 76.2%); Method C: Lithium bromide (0.011 g, 0.12 mmol) and 15a
(0.020 g, 0.041 mmol) were added to vials in the dry box, followed by the addition of
CDCl3 to each vial. The contents of the vials were mixed and placed into a NMR tube.
Quantitative formation of 3 was observed by 1H, 13C and 31P NMR spectroscopy; mp
1 4 155-157°C; H NMR (600 MHz) δ 7.66 (d, JPH = 3.0 Hz, 1H), 7.48-7.50 (m, 2H), 7.39-
133 3 7.45 (m, 8H), 2.76-2.78 (m, 2H), 2.41-2.43 (m, 2H), 2.01 (pent, JHH = 7.8 Hz, 2H), 1.40
3 13 1 3 (s, 9H), 0.71 (d, JPH = 3.0 Hz, 3H); C{ H} NMR δ 158.0 (d, JPC = 6.3 Hz), 152.2 (d,
2 1 2 4 JPC = 14.6 Hz), 136.0 (d, JPC = 38.7 Hz), 133.4 (d, JPC = 12.0 Hz), 131.3 (d, JPC = 2.4
3 1 2 Hz), 129.0 (d, JPC = 10.8 Hz), 128.9 (d, JPC = 67.5 Hz), 63.6, 38.1 (bs), 37.3 (d, JPC =
3 2 31 1 11.1 Hz), 31.3, 23.1 (d, JPC = 6.0 Hz), 2.0 (d, JPC = 0.4 Hz); P{ H} NMR δ 28.5; IR
3050 (w), 2960 (s), 2923 (s), 2850 (s), 2722 (w), 2676 (w), 2199 (w), 1957 (w), 1884 (w),
1811 (w), 1699 (w), 1582 (w), 1463 (m), 1436 (m), 1380 (m), 1371 (m), 1307 (w), 1257
(w), 1225 (w), 1197 (w), 1161 (m), 1097 (m), 1023 (w), 987 (w), 964 (w), 913 (m), 890
(w), 845 (w), 794 (w), 730 (m), 693 (m), 643 (m); Anal. Calcd for C23H29BrNPPd: C,
51.46; H, 5.45; N, 2.61. Found: C, 51.70; H, 5.51; N, 2.29.
2 t (Ph -Pen- Bu)Pd(CH3)OTf (16). Method A: To a stirring slurry of silver triflate (0.233
g, 0.908 mmol) in dichloromethane (20 mL), a solution of 15a (0.406 g, 0.825 mmol) in
dichloromethane (20 mL) was added and stirred at ambient temperature for 4 h in the
absence of light. Solvent was removed and the yellow solid was dissolved in
dichloromethane and precipitated with pentane (0.378 g, 75.6%); Method B: To a
stirring slurry of silver triflate (0.233 g, 0.908 mmol) in dichloromethane (20 mL), a
solution of 15b (0.443 g, 0.825 mmol) in dichloromethane (20 mL) was added and stirred
at ambient temperature for 4 h in the absence of light. Solvent was removed and the
yellow solid was dissolved in dichloromethane and precipitated with pentane (0.343 g,
1 4 68.6%); mp 153-154°C; H NMR (600 MHz) δ 7.75 (d, JPH = 2.4 Hz, 1H), 7.51-7.53 (m,
3 2H), 7.42-7.48 (m, 8H), 2.82-2.84 (m, 2H), 2.39-2.42 (m, 2H), 2.03 (pent, JHH = 7.2 Hz,
13 1 3 2 2H), 1.37 (s, 9H), 0.70 (bs, 3H); C{ H} NMR δ 157.2 (d, JPC = 5.7 Hz), 152.9 (d, JPC
1 2 4 = 14.1 Hz), 134.4 (d, JPC = 6.3 Hz), 133.2 (d, JPC = 12.0 Hz), 131.9 (d, JPC = 2.6 Hz),
134 3 1 3 129.2 (d, JPC = 11.7 Hz), 128.0 (d, JPC = 57.8 Hz), 64.0, 38.0 (d, JPC = 2.6 Hz), 37.7 (d,
2 3 31 1 19 1 JPC = 12.3 Hz), 30.3, 23.1 (d, JPC = 6.2 Hz), 6.6; P{ H} NMR δ 30.0; F{ H} NMR δ
-78.2; IR 3053 (w), 2956 (s), 2920 (s), 2849 (s), 2724 (w), 2687 (w), 2314 (w), 1680 (w),
1622 (w), 1584 (m), 1530 (w), 1463 (s), 1438 (s), 1375 (m), 1337 (w), 1300 (s), 1258
(m), 1233 (s), 1208 (s), 1170 (s), 1103 (m), 1070 (m), 1019 (s), 994 (m), 961 (m), 894
(w), 798 (m), 748 (m), 697 (m), 635 (s); Anal. Calcd for C24H29F3NO3PPdS · 0.3 CH2Cl2:
C, 46.22; H, 4.73; N, 2.22. Found: C, 46.38; H, 4.30; N, 2.60.
Crystallography. Summaries of crystal data and collection parameters for crystal
structures of 9a, 9a’, 9d-f, 9h, 9j, 9k, 9m, 10a, and 11-16 are provided in Tables 12-21.
Detailed descriptions of data collection, as well as data solution, are provided below.
ORTEP diagrams were generated with the ORTEP-3256 software package. For each
sample, a suitable crystal was mounted on a pulled glass fiber using Paratone-N
hydrocarbon oil. The crystal was transferred to a Siemens SMART diffractometer with a
CCD area detector, centered in the X-ray beam, and cooled to 140 or 175 K using a
nitrogen-flow low-temperature apparatus that had been precisely calibrated by a
thermocouple placed at the same position as the crystal. An arbitrary hemisphere of data
was collected using 0.3° ω scans, and the data were integrated by the program SAINT.258
The final unit cell parameters were determined by a least-squares refinement of the reflections with I > 10σ(I). Data analysis using Siemens XPREP259 and the successful
solution and refinement of the structure determined the space group. Empirical
absorption corrections were applied for 9-16 using the program SADABS.260 Equivalent reflections were averaged, and the structures were solved by direct methods using the
135 SHELXTL software package.261 Unless otherwise noted, all non-hydrogen atoms were
refined anisotropically, and hydrogen atoms were included as fixed atoms but not refined.
Compound 9a. X-ray quality crystals were grown from a layered solution of methylene chloride and diethyl ether at room temperature. 1.5 molecules of disordered methylene chloride existed in the unit cell and were refined isotropically. Hydrogen atoms were included for all ordered atoms. The final cycle of full-matrix least-squares refinement was based on 6817 observed reflections and 301 variable parameters and converged yielding final residuals: R = 0.0434, Rall = 0.0539, and GOF = 0.836.
Compound 9a’ (Figure 26). X-ray quality crystals were grown from a saturated solution
of chloroform at room temperature. 1 molecule of chloroform existed in the asymmetric
unit and was refined anisotropically. The final cycle of full-matrix least-squares
refinement was based on 6833 observed reflections and 260 variable parameters and
converged yielding final residuals: R = 0.0713, Rall = 0.0759, and GOF = 1.041.
Compound 9d (Figure 27). X-ray quality crystals were grown from a layered solution of
methylene chloride and diethyl ether at room temperature. An inversion twin was present with a ratio of 80:20 of P41:P43. In order to refine the inversion twin, a TWIN refinement was used as well as an extinction refinement. The final cycle of full-matrix least-squares refinement was based on 13174 observed reflections and 597 variable parameters and converged yielding final residuals: R = 0.0348, Rall = 0.0381, and GOF = 1.001.
Compound 9e (Figure 28). X-ray quality crystals were grown from a layered solution of methylene chloride and diethyl ether at room temperature. The final cycle of full-matrix least-squares refinement was based on 6942 observed reflections and 316 variable
136 parameters and converged yielding final residuals: R = 0.0299, Rall = 0.0335, and GOF =
1.100.
Compound 9f (Figure 29). X-ray quality crystals were grown from a layered solution of methylene chloride and diethyl ether at room temperature. 1 molecule of methylene chloride was present in the asymmetric unit and was refined anisotropically. The tert-
butyl group of the imine ring was disordered. Hydrogen atoms were included for all
ordered atoms. The final cycle of full-matrix least-squares refinement was based on 4664
observed reflections and 322 variable parameters and converged yielding final residuals:
R = 0.0437, Rall = 0.0560, and GOF = 1.006.
Compound 9h. X-ray quality crystals were grown from a layered solution of methylene
chloride and diethyl ether at room temperature. There were 2 regions in the asymmetric unit which contained a partial equivalent of disordered methylene chloride and were
refined anisotropically. Hydrogen atoms were included for all ordered atoms. The final
cycle of full-matrix least-squares refinement was based on 7002 observed reflections and
295 variable parameters and converged yielding final residuals: R = 0.0458, Rall = 0.0525
and GOF = 1.063.
Compound 9j (Figure 30). X-ray quality crystals were grown from a layered solution of methylene chloride and diethyl ether at room temperature. The final cycle of full-matrix
least-squares refinement was based on 3773 observed reflections and 308 variable
parameters and converged yielding final residuals: R = 0.1193, Rall = 0.1279, and GOF =
0.945.
Compound 9k (Figure 31). X-ray quality crystals were grown from a layered solution of
methylene chloride and diethyl ether at room temperature. The final cycle of full-matrix
137 least-squares refinement was based on 7093 observed reflections and 325 variable
parameters and converged yielding final residuals: R = 0.0310, Rall = 0.0486, and GOF =
1.032.
Compound 9m. X-ray quality crystals were grown from a layered solution of methylene
chloride and diethyl ether at room temperature. 1 molecule of methylene chloride was in
the asymmetric unit and was refined anisotropically. The final cycle of full-matrix least-
squares refinement was based on 6031 observed reflections and 220 variable parameters
and converged yielding final residuals: R = 0.0510, Rall = 0.0582, and GOF = 1.062
Compound 10a. X-ray quality crystals were grown from a saturated solution of diethyl
ether at -25 °C. The final cycle of full-matrix least-squares refinement was based on
5981 observed reflections and 262 variable parameters and converged yielding final
residuals: R = 0.0269, Rall = 0.0311, and GOF = 1.062.
Compound 11a. X-ray quality crystals were grown from a layered solution of
tetrahydrofuran and pentane at ambient temperature. The final cycle of full-matrix least-
squares refinement was based on 6557 observed reflections and 325 variable parameters
and converged yielding final residuals: R = 0.0286, Rall = 0.0348, and GOF = 1.043.
Compound 11c. X-ray quality crystals were grown from a layered solution of tetrahydrofuran and pentane at ambient temperature. The asymmetric unit contains two independent [(3IP)Pd(allyl)]+ cations. One is fully ordered as the trans isomer, while the
second has an allyl group with a disordered central carbon atom, giving a 1:1 cis/trans
ratio. Thus, the overall crystal structure contains a 3:1 trans:cis ratio of isomers.
- Additionally, the two equivalents of PF6 necessary for charge balance are present as one
- fully occupied PF6 (with one disordered fluorine) and two P0.5F3 units located at special
138 positions: 0, 0, z and ½, 0, z. The final cycle of full-matrix least-squares refinement was
based on 13318 observed reflections and 653 variable parameters and converged yielding final residuals: R = 0.0494, Rall = 0.0844, and GOF = 0.867.
Compound 12a. X-ray quality crystals were grown from a saturated solution of diethyl
ether at -25°C. The final cycle of full-matrix least-squares refinement was based on 6902
observed reflections and 293 variable parameters and converged yielding final residuals:
R = 0.0296, Rall = 0.0436 and GOF = 0.995.
Compound 13a. X-ray quality crystals were grown from a layered solution of THF and
pentane at ambient temperature. The asymmetric unit contained one equivalent of
t CH2Cl2 in addition to dimeric 13 and was refined anisotropically. One Bu group was
disordered over two rotational positions. The final cycle of full-matrix least-squares
refinement was based on 13270 observed reflections and 623 variable parameters and
converged yielding final residuals: R = 0.0576, Rall = 0.0594, and GOF = 1.152.
Compound 14. X-ray quality crystals were grown from a layered solution of THF and
pentane at ambient temperature. The final cycle of full-matrix least-squares refinement
was based on 6933 observed reflections and 370 variable parameters and converged yielding final residuals: R = 0.0322, Rall = 0.0394, and GOF 1.021.
Compound 15a. X-ray quality crystals were grown from a saturated solution of diethyl
ether at ambient temperature. The final cycle of full-matrix least-squares refinement was based on 5629 observed reflections and 244 variable parameters and converged yielding
final residuals: R = 0.0306, Rall = 0.0328, and GOF = 1.108.
Compound 15b. X-ray quality crystals were grown from a layered solution of
dichloromethane and diethyl ether at ambient temperature. The final cycle of full-matrix
139 least-squares refinement was based on 5838 observed reflections and 244 variable
parameters and converged yielding final residuals: R = 0.0516, Rall = 0.0677, and GOF =
1.067.
Compound 15b’. X-ray quality crystals were grown from a layered solution of THF and pentane at ambient temperature. The final cycle of full-matrix least-squares refinement was based on 5504 observed reflections and 244 variable parameters and converged yielding final residuals: R = 0.0367, Rall = 0.0464, and GOF = 0.960.
Compound 16. X-ray quality crystals were grown from a layered solution of
dichloromethane and diethyl ether at ambient temperature. The final cycle of full-matrix
least-squares refinement was based on 6343 observed reflections and 307 variable
parameters and converged yielding final residuals: R = 0.0319, Rall = 0.0335, and GOF =
1.091.
140 Table 12. Crystal Data and Collection Parameters
Compound 9a 9a’
formula C22H26Cl2NPPd · 1.5 CH2Cl2 C22H26Cl2NPPd · CHCl3 fw 640.15 632.15
space group P21/n (#14) P21/n (#14) temperature (K) 140 175 a (Å) 12.669(1) 7.853(1) b (Å) 15.035(1) 22.086(2) c (Å) 14.120(1) 15.588(2) α (deg) 90.000 90.000 β (deg) 94.963(2) 99.315(2) γ (deg) 90.000 90.000 V (Å 3) 2679.5(5) 2528.3(5) Z 4 4 3 densitycalc (g/cm ) 1.271 1.574 diffractometer Siemens SMART Siemens SMART radiation Mo Kα (λ = 0.71069 Å) Mo Kα (λ = 0.71069 Å) monochromator graphite graphite detector CCD area detector CCD area detector scan type, width ω, 0.3° ω, 0.3° scan speed 20.0 s/frame 20.0 s/frame no. of reflns measd hemisphere hemisphere 2θ range (deg) 4.5-57.1 4.5-57.1 cryst dimens (mm) 0.30 x 0.24 x 0.06 0.40 x 0.18 x 0.08 no. of reflns measd 30524 31113 no. of unique reflns 6817 6833 no. of observations 6817 6833 no. of params 301 260
R, Rw, Rall 0.0434, 0.1196, 0.0539 0.0713, 0.1805, 0.0759 GOF 0.836 1.041
141 Table 13. Crystal Data and Collection Parameters
Compound 9d 9e
formula C28H30Cl2NPPd C30H34Cl2NPPd fw 588.80 616.94
space group P41 P21/n (#14) temperature (K) 175 175 a (Å) 12.712(1) 12.222(1) b (Å) 12.712(1) 13.392(1) c (Å) 32.865(2) 17.989(2) α (deg) 90.000 90.000 β (deg) 90.000 108.821(2) γ (deg) 90.000 90.000 V (Å 3) 5311.0(5) 2786.9(5) Z 8 4 3 densitycalc (g/cm ) 1.473 1.470 diffractometer Siemens SMART Siemens SMART
radiation Mo Kα (λ = 0.71069 Å) Mo Kα (λ = 0.71069 Å) monochromator graphite graphite detector CCD area detector CCD area detector scan type, width ω, 0.3° ω, 0.3° scan speed 20.0 s/frame 30.0 s/frame no. of reflns measd hemisphere hemisphere 2θ range (deg) 4.7-55.9 4.7-56.6 cryst dimens (mm) 0.22 x 0.14 x 0.08 0.18 x 0.16 x 0.08 no. of reflns measd 60387 31507 no. of unique reflns 13174 6942 no. of observations 13174 6942 no. of params 597 316
R, Rw, Rall 0.0348, 0.0870, 0.0381 0.0299, 0.0757, 0.0335 GOF 1.001 1.100
142 Table 14. Crystal Data and Collection Parameters
Compound 9f 9h
formula C28H30Cl2NPPd · CH2Cl2 C23H28Cl2NPPd · 1.5 CH2Cl2 fw 673.81 654.20
space group P-1 (#2) P21/n (#14) temperature (K) 175 175 a (Å) 8.272(2) 12.635(1) b (Å) 14.171(3) 15.167(1) c (Å) 14.272(3) 14.643(1) α (deg) 73.573(5) 90.000 β (deg) 76.447(5) 92.545(2) γ (deg) 75.881(5) 90.000 V (Å 3) 1531.5(6) 2803.4(3) Z 2 4 3 densitycalc (g/cm ) 1.441 1.557 diffractometer Siemens SMART Siemens SMART
radiation Mo Kα (λ = 0.71069 Å) Mo Kα (λ = 0.71069 Å) monochromator graphite graphite detector CCD area detector CCD area detector scan type, width ω, 0.3° ω, 0.3° scan speed 30.0 s/frame 20.0 s/frame no. of reflns measd hemisphere hemisphere 2θ range (deg) 4.8-56.8 5.0-56.6 cryst dimens (mm) 0.24 x 0.14 x 0.08 0.22 x 0.16 x 0.08 no. of reflns measd 10322 32040 no. of unique reflns 4664 7002 no. of observations 4664 7002 no. of params 322 295
R, Rw, Rall 0.0437, 0.1212, 0.0560 0.0458, 0.1210, 0.0525 GOF 1.006 1.063
143 Table 15. Crystal Data and Collection Parameters
Compound 9j 9k
formula C29H32Cl2NPPd C31H36Cl2NPPd fw 602.83 630.97
space group P21/n (#14) P21/n (#14) temperature (K) 140 140 a (Å) 9.739(2) 12.333(3) b (Å) 14.885(2) 13.423(3) c (Å) 18.120(3) 17.773(4) α (deg) 90.000 90.000 β (deg) 91.027(4) 105.979(5) γ (deg) 90.000 90.000 V (Å 3) 2625.7(7) 2828.5(1) Z 4 4 3 densitycalc (g/cm ) 1.525 1.481 diffractometer Siemens SMART Siemens SMART
radiation Mo Kα (λ = 0.71069 Å) Mo Kα (λ = 0.71069 Å) monochromator graphite graphite detector CCD area detector CCD area detector scan type, width ω, 0.3° ω, 0.3° scan speed 30.0 s/frame 20.0 s/frame no. of reflns measd hemisphere hemisphere 2θ range (deg) 4.5-56.7 4.6-56.5 cryst dimens (mm) 0.22 x 0.14 x 0.10 0.22 x 0.14 x 0.04 no. of reflns measd 19590 32061 no. of unique reflns 3773 7093 no. of observations 3773 7093 no. of params 308 325
R, Rw, Rall 0.1193, 0.2999, 0.1279 0.0310, 0.0766, 0.0486 GOF 0.945 1.032
144 Table 16. Crystal Data and Collection Parameters
Compound 9m 10a
formula C18H34Cl2NPPd · CH2Cl2 C25H31ClNPPd fw 557.75 518.35
space group P21/n (#14) P21/c (#14) temperature (K) 140 140 a (Å) 16.195(2) 9.9685(6) b (Å) 10.128(1) 13.7786(9) c (Å) 16.204(2) 17.649(1) α (deg) 90.000 90.000 β (deg) 114.580(2) 97.424(1) γ (deg) 90.000 90.000 V (Å 3) 2416.9(5) 2403.9(3) Z 4 4 3 densitycalc (g/cm ) 1.533 1.432 diffractometer Siemens SMART Siemens SMART
radiation Mo Kα (λ = 0.71069 Å) Mo Kα (λ = 0.71069 Å) monochromator graphite graphite detector CCD area detector CCD area detector scan type, width ω, 0.3° ω, 0.3° scan speed 20.0 s/frame 10.0 s/frame no. of reflns measd hemisphere hemisphere 2θ range (deg) 4.9-56.7 4.6-56.6 cryst dimens (mm) 0.30 x 0.30 x 0.10 0.40 x 0.40 x 0.24 no. of reflns measd 27278 25085 no. of unique reflns 6031 5981 no. of observations 6031 5981 no. of params 220 262
R, Rw, Rall 0.0510, 0.1368, 0.0582 0.0269, 0.0682, 0.0311 GOF 1.062 1.062
145 Table 17. Crystal Data and Collection Parameters
Compound 11a 11c
formula C26H31F3NO3PPdS C50H62F12N2P4Pd2 fw 631.99 1255.86
space group P21/c (#14) Iba2 (#45) temperature (K) 140 140 a (Å) 11.2833(5) 21.604(1) b (Å) 8.8106(4) 27.913(1) c (Å) 26.981(1) 17.792(2) α (deg) 90.000 90.000 β (deg) 99.783(1) 90.000 γ (deg) 90.000 90.000 V (Å 3) 2643.3(2) 10729(1) Z 4 8 3 densitycalc (g/cm ) 1.588 1.555 diffractometer Siemens SMART Siemens SMART
radiation Mo Kα (λ = 0.71069 Å) Mo Kα (λ = 0.71069 Å) monochromator graphite graphite detector CCD area detector CCD area detector scan type, width ω, 0.3° ω, 0.3° scan speed 20.0 s/frame 20.0 s/frame no. of reflns measd hemisphere hemisphere 2θ range (deg) 4.9-56.3 4.6-48.2 cryst dimens (mm) 0.30 x 0.08 x 0.06 0.30 x 0.15 x 0.02 no. of reflns measd 29066 113063 no. of unique reflns 6557 13318 no. of observations 6557 13318 no. of params 325 653
R, Rw, Rall 0.0286, 0.0670, 0.0348 0.0494, 0.1199, 0.0844 GOF 1.043 0.867
146 Table 18. Crystal Data and Collection Parameters
Compound 12a 13a
formula C26H37Cl2N2PPd C46H52Cl2F6N2O6P2Pd2S2 · CH2Cl2 fw 585.85 1337.72
space group Pbcn (#60) P21 (#4) temperature (K) 140 140 a (Å) 28.334(1) 9.485(1) b (Å) 10.179(1) 10.534(1) c (Å) 19.203(1) 26.883(1) α (deg) 90.000 90.000 β (deg) 90.000 90.804(1) γ (deg) 90.000 90.000 V (Å 3) 5538.4(1) 2685.9(1) Z 8 2 3 densitycalc (g/cm ) 1.405 1.646 diffractometer Siemens SMART Siemens SMART radiation Mo Kα (λ = 0.71069 Å) Mo Kα (λ = 0.71069 Å) monochromator graphite graphite detector CCD area detector CCD area detector scan type, width ω, 0.3° ω, 0.3° scan speed 20.0 s/frame 20.0 s/frame no. of reflns measd hemisphere hemisphere 2θ range (deg) 4.5-56.6 4.5-56.5 cryst dimens (mm) 0.32 x 0.28 x 0.04 0.48 x 0.22 x 0.04 no. of reflns measd 63537 61781 no. of unique reflns 6902 13270 no. of observations 6902 13270 no. of params 293 623
R, Rw, Rall 0.0296, 0.0827, 0.0436 0.0576, 0.1452, 0.0594 GOF 0.995 1.152
147 Table 19. Crystal Data and Collection Parameters
Compound 14 15a
formula C24H26F6NO6PPdS2 C23H29ClNPPd fw 739.95 492.29
space group P21/c (#14) P21/n (#14) temperature (K) 140 140 a (Å) 18.658(1) 8.830(1) b (Å) 10.556(1) 16.792(1) c (Å) 14.722(1) 15.270(1) α (deg) 90.000 90.000 β (deg) 106.146(2) 93.184(1) γ (deg) 90.000 90.000 V (Å 3) 2785.1(1) 2260.6(1) Z 4 4 3 densitycalc (g/cm ) 1.765 1.446 diffractometer Siemens SMART Siemens SMART radiation Mo Kα (λ = 0.71069 Å) Mo Kα (λ = 0.71069 Å) monochromator graphite graphite detector CCD area detector CCD area detector scan type, width ω, 0.3° ω, 0.3° scan speed 20.0 s/frame 20.0 s/frame no. of reflns measd hemisphere hemisphere 2θ range (deg) 5.0-56.6 5.2-56.6 cryst dimens (mm) 0.68 x 0.15 x 0.15 0.38 x 0.10 x 0.08 no. of reflns measd 31988 25894 no. of unique reflns 6933 5629 no. of observations 6933 5629 no. of params 370 244
R, Rw, Rall 0.0322, 0.0878, 0.0394 0.0306, 0.0785, 0.0328 GOF 1.021 1.108
148 Table 20. Crystal Data and Collection Parameters
Compound 15b 15b’
formula C23H29BrNPPd C23H29BrNPPd fw 536.75 536.75
space group P21/c (#14) P-1 (#2) temperature (K) 140 140 a (Å) 13.944(1) 9.480(1) b (Å) 9.840(1) 9.936(1) c (Å) 17.190(1) 12.549(1) α (deg) 90.000 73.030(1) β (deg) 95.697(2) 79.326(1) γ (deg) 90.000 86.795(1) V (Å 3) 2346.9(3) 1110.9(1) Z 4 2 3 densitycalc (g/cm ) 1.519 1.605 diffractometer Siemens SMART Siemens SMART
radiation Mo Kα (λ = 0.71069 Å) Mo Kα (λ = 0.71069 Å) monochromator graphite graphite detector CCD area detector CCD area detector scan type, width ω, 0.3° ω, 0.3° scan speed 20.0 s/frame 20.0 s/frame no. of reflns measd hemisphere hemisphere 2θ range (deg) 4.8-56.5 4.3-56.7 cryst dimens (mm) 0.16 x 0.14 x 0.06 0.32 x 0.10 x 0.04 no. of reflns measd 26518 12552 no. of unique reflns 5838 5504 no. of observations 5838 5504 no. of params 244 244
R, Rw, Rall 0.0516, 0.1717, 0.0677 0.0367, 0.0852, 0.0464 GOF 1.067 0.960
149 Table 21. Crystal Data and Collection Parameters
Compound 16
formula C24H29F3NO3PPdS fw 605.99
space group P212121 (#19) temperature (K) 140 a (Å) 10.079(1) b (Å) 15.819(1) c (Å) 15.947(1) α (deg) 90.000 β (deg) 90.000 γ (deg) 90.000 V (Å 3) 2542.4(1) Z 4 3 densitycalc (g/cm ) 1.588 diffractometer Siemens SMART
radiation Mo Kα (λ = 0.71069 Å) monochromator graphite detector CCD area detector scan type, width ω, 0.3° scan speed 20.0 s/frame no. of reflns measd hemisphere 2θ range (deg) 4.8-56.6 cryst dimens (mm) 0.42 x 0.09 x 0.06 no. of reflns measd 29311 no. of unique reflns 6343 no. of observations 6343 no. of params 307
R, Rw, Rall 0.0319, 0.0777, 0.0335 GOF 1.091
150 Figure 26. ORTEP diagram (50% thermal ellipsoids) of 9a’. Hydrogen atoms and chloroform molecule omitted for clarity. Bond lengths (in Å): Pd1-P1 = 2.207(1),
Pd1-N1 = 2.072(4), N1-C1 = 1.282(6), C1-C2 = 1.460(7), C2-C3 = 1.342(7). Bond angles (in deg): P1-Pd1-N1 = 86.5(1), Cl1-Pd1-Cl2 = 90.0(1), N1-C1-C2 = 125.6(5),
C1-C2-C3 = 124.5(4).
Figure 27. ORTEP diagram (50% thermal ellipsoids) of 9d. Hydrogen atoms omitted for clarity. An inversion twin with a ratio of 80:20 (P41:P43) was present.
Bond lengths (in Å): Pd1-P1 = 2.216(1), Pd2-P2 = 2.220(1), Pd1-N1 = 2.058(3), Pd2-
N2 = 2.073(3). Bond angles (in deg): P1-Pd1-N1 = 91.9(1), P2-Pd2-N2 = 90.8(1),
Cl1-Pd1-Cl2 = 89.7(1), Cl3-Pd2-Cl4 =89.6(1).
151
Figure 28. ORTEP diagram (50% thermal ellipsoids) of 9e. Hydrogen atoms omitted for clarity. Bond lengths (in Å): Pd1-P1 = 2.224(1), Pd1-N1 = 2.073(2), N1-C1 =
1.284(2), C1-C2 = 1.453(3), C2-C3 = 1.339(3). Bond angles (in deg): P1-Pd1-N1 =
90.4(1), Cl1-Pd1-Cl2 = 89.6(1), N1-C1-C2 = 128.0(2), C1-C2-C3 = 127.5(2).
Figure 29. ORTEP diagram (50% thermal ellipsoids) of 9f. Hydrogen atoms and disordered atoms of the tert-butyl omitted for clarity. Bond lengths (in Å): Pd1-P1 =
2.214(1), Pd1-N1 = 2.066(3), N1-C1 = 1.290(5), C1-C2 = 1.447(5), C2-C3 =
1.352(6). Bond angles (in deg): P1-Pd1-N1 = 87.7(1), Cl1-Pd1-Cl2 = 91.2(1), N1-
C1-C2 = 125.6(4), C1-C2-C3 = 125.7(4).
152 Figure 30. ORTEP diagram (50% thermal ellipsoids) of 9j. Hydrogen atoms omitted for clarity. Bond lengths (in Å): Pd1-P1 = 2.210(2), Pd1-N1 = 2.051(6), N1-C1 =
1.294(8), C1-C2 = 1.475(9), C2-C3 = 1.334(9). Bond angles (in deg): P1-Pd1-N1 =
91.5(2), Cl1-Pd1-Cl2 = 88.3(1), N1-C1-C2 = 129.3(6), C1-C2-C3 = 125.2(6).
Figure 31. ORTEP diagram (50% thermal ellipsoids) of 9k. Hydrogen atoms omitted for clarity. Bond lengths (in Å): Pd1-P1 = 2.226(1), Pd1-N1 = 2.069(2), N1-
C1 = 1.290(3), C1-C2 = 1.466(3), C2-C3 = 1.346(3). Bond angles (in deg): P1-Pd1-
N1 = 89.0(1), Cl1-Pd1-Cl2 = 89.1(1), N1-C1-C2 = 129.9(2), C1-C2-C3 = 125.7(2).
153 III-4: Conclusion
A wide variety of 3-iminophosphine palladium complexes, with an emphasis on compounds relevant to catalytic hydroamination and similar cross-coupling reactions were synthesized. The halogenated and alkylated palladium complexes were readily converted to highly electrophilic complexes through the use of weakly coordinating counterions. Additionally, these halide complexes have a strong affinity for a diverse set of amine ligands. Numerous examples of both η1 and η2 coordinated 3-iminophosphine ligands support that hemilabile traits are quite common in this ligand set.
154
Chapter 4
──────────────────────────────
Hydroamination and Cross-Coupling Using
3-Iminophosphine Palladium(II) Complexes
──────────────────────────────
155 IV-1: Introduction
One of the most efficient means for the synthesis of complex organic molecules is
through the use of metal catalysts with low cost substrates. Since catalysts lower the
activation energy required for a specific reaction, they have been important for the
transformation of a wide array of molecules over the past 70 years.1-3 Homogeneous
catalysts are often employed in the fine-chemical and pharmaceutical industries because
of their ability to produce highly selective and reproducible products. Moreover,
homogeneous catalysts are generally more reactive than their heterogeneous counterparts,
although they require substantial product purification.70
The wide use of amines and their derivatives across many fields of chemistry has
led to considerable interest concerning the synthesis of carbon-nitrogen bonds.
Compounds containing carbon-nitrogen bonds are commonly found in biologically-active
natural and synthetic products, key reactions in organic chemistry, and throughout the
pharmaceutical and fine-chemical industries. One of the most attractive routes for
carbon-nitrogen bond formation is through the hydroamination of unsaturated carbon-
carbon double and triple bonds by primary or secondary amines, due in part to this
reaction’s 100% atom efficiency. The formation of carbon-nitrogen bonds via
hydroamination can occur through intramolecular or intermolecular processes,17, 283-285 although the latter are generally of greater value due to the large array of commercially available, low-cost substrates. Typically, intermolecular hydroamination is harder to achieve due to the higher entropic demands and slower reaction kinetics, thus requiring a more active and selective catalyst than intramolecular hydroamination. The products generated by intermolecular hydroamination include secondary and tertiary amines,
156 diamines, imines and enamines. There are several reports of the intermolecular hydroamination of alkenes,6, 36, 41, 42, 59 dienes,33, 36, 39, 141, 144, 286 vinyl arenes,29, 36, 148, 158,
162, 177 and alkynes,6, 38, 42, 60, 138, 156, 287-290 but few examples involving cyclic dienes107, 145,
168, 291, 292 as substrates.
Imines and enamines are useful compounds because they function as reagents for
the introduction of nitrogen-containing moieties into a synthetic sequence. Specifically,
imines are commonly employed in carbon-carbon bond formation, as seen in Mannich
reactions and aza Diels-Alder cycloadditions.242 Additionally, they are readily reduced to
the corresponding secondary amines.242 Ketimines are commonly targeted as
hydroamination products because alternative synthetic pathways often involve the need
for elevated temperatures, an acid catalyst and/or a water scavenger, imposing functional
group limitations, and/or a lack of regio- and stereochemical control. Enamines comprise
another important synthetic target due to the subsequent reactivity of their double bonds, often employed as substrates for addition or redox reactions.243, 293 Current methods for
enamine synthesis include allylic amination243 and Buchwald-Hartwig coupling.94, 294
Only a few studies have shown the catalytic addition of amines to cyclic dienes.107, 145, 168,
291 A more thorough investigation of the catalysts for this reaction is necessary in order
to develop an efficient route to enamines that has substrate tolerance coupled with high
catalytic activity.
Biaryls are another class of important synthetic intermediates in the synthesis of
fine-chemicals, polymers, and a wide range of alkaloids.98, 190 Although a variety of
catalysts have been reported, some of which are commercially available, few demonstrate
wide functional group tolerance in tandem with minimal steric hindrance effects.98
157 Moreover, since the use of biaryls is of commercial importance, it is imperative that the starting materials be cost-effective for these reactions.
IV-2: Results and Discussion
Hydroamination
To demonstrate the utility of the 3-iminophosphine ligand set as ancillary ligands for hydroamination, compounds 3p, 9a, 10a, and 11a were screened as potential catalysts
(Scheme 27). A series of vials containing 5 mol% metal catalyst, 1 equivalent of amine,
6 equivalents of diene and 1 mL of methylene chloride were heated to 50°C for 22 hours.
100 μL of dodecane was added to the reaction vial as an internal standard, and product distribution was determined via gas chromatography. 1H and 13C NMR spectra were obtained after column chromatography. The hydroamination of 1,3-cyclohexadiene with primary and secondary amines using 3p, 9a, 10a, and 11a as the catalyst is summarized in Table 22. Entries 1-4 show that compounds 3p, 9a, and 10a display almost no catalytic activity, while compound 11a successfully catalyzed the hydroamination of 1,3- cyclohexadiene. Moreover, entries 4-6 show that 11a readily converted morpholine and piperidine into the corresponding 1,4-hydroaminated enamines, while the activity is much lower for benzylamine. For each of these, the relative activities are lower than those observed previously using related diphosphine complexes.107, 145
cat. + HNRR' NRR' A
cat. NR' NRR' Ph H + HNRR' Ph or Ph B
(R = H) (R ≠ H) Scheme 27. Hydroamination of 1,3-cyclohexadiene (A) and phenylacetylene (B).
158 The effects of the 1,3-cyclohexadiene to morpholine ratio and the reaction solvent on the catalytic hydroamination using compound 11a are represented in Table 23.
Entries 1-6 demonstrate a direct correlation between the ratio of diene to amine and the percent conversion with the catalytic rate increasing as a result of higher substrate (diene) concentration. Furthermore, two byproducts, benzene and cyclohexene, were observed for this catalysis, which were the result of dehydrogenation/hydrogenation of 1,3- cyclohexadiene. Entries 7-10 show the effect of solvent on this catalysis. Lewis bases such as tetrahydrofuran and 1,4-dioxane function as competitive inhibitors, due to their ability to bind to open coordination sites on the active palladium species, leading to substantially less conversion to product. The low solubility of 11a in toluene leads to its virtual inactivity. The use of chloroform as reaction solvent provides moderate
Table 22. Hydroamination of 1,3-cyclohexadiene using 3p, 9a, 10a, 11aa
Entry Amine Catalyst Yield[%]b
1 Morpholine 3IP (3p) 0
2 Morpholine (3IP)PdCl2 (9a) 0 3 Morpholine (3IP)Pd(allyl)Cl (10a) 4 4 Morpholine [(3IP)Pd(allyl)][OTf] (11a) 52 5 Piperidine [(3IP)Pd(allyl)][OTf] (11a) 31 6 Benzylamine [(3IP)Pd(allyl)][OTf] (11a) 9
aReaction conditions: 3.6 mmol of 1,3-cyclohexadiene, 0.60 mmol of
b amine, 0.030 mmol catalyst, 50°C, CH2Cl2, 22 h. Determined by
average of 2 GC runs. conversion to the 1,4-hydroamination product at 50°C, although with somewhat lower rates than those observed in dichloromethane. Increasing the reaction temperature when
159 using chloroform, 1,4-dioxane, tetrahydrofuran, and toluene as reaction solvent improves the product yields, but with an overall lower conversion when compared to that observed in dichloromethane at 50°C.
Table 23. Effect of 1,3-cyclohexadiene to morpholine
ratio and solvent effectsa
Entry Diene:Amine Solvent Yield[%]b
1 1:1 CH2Cl2 25
2 2:1 CH2Cl2 35
3 4:1 CH2Cl2 41
4 6:1 CH2Cl2 52
5 8:1 CH2Cl2 58
6 10:1 CH2Cl2 62 7 4:1 THF 2 8 4:1 Dioxane 2 9 4:1 Toluene 1 10 4:1 Chloroform 30
aReaction conditions: 0.030 mmol 11a (5 mol%), 50°C, 22
h. bDetermined by average of 2 GC runs.
The effects of the amount of solvent used for the hydroamination of 1,3- cyclohexadiene with morpholine are illustrated in terms of amine concentration in Figure
32. The data clearly indicate that increasing the molar concentration increases the overall conversion. At these higher substrate concentrations, the observed activities for the catalytic hydroamination of 1,3-cyclohexadiene with morpholine were quite comparable to that in previous reports107, 145, 291 with the advantage that our system does not require the necessity of an acid cocatalyst.
160 % Yield vs. Concentration
100
80
60 R2 = 0.8866 40 % Yield
20
0 0 0.2 0.4 0.6 0.8 1 [Amine]
Figure 32. Effect of concentration on the hydroamination of 1,3-cyclohexadiene with
morpholine in the presence of 11a. Reaction conditions: 6:1:0.05 ratio of 1,3-
cyclohexadiene to morpholine to 11a. Percent yield determined by the average of 2
GC runs.
The hydroamination of phenylacetylene to form imines and enamines is also an
important transformation (Scheme 27). As such, our catalyst system was employed for
the hydroamination of phenylacetylene using a variety of amines (Table 24). This
reaction proved to be quite versatile, with successful catalysis using both primary and
secondary amines. The primary amines tautomerized to the Markovnikov imine, while
the secondary amines yielded the Markovnikov enamine. The observed catalytic rates
were similar to other catalysts.140, 295 A large excess of phenylacetylene was necessary for the catalysis due to the competing cyclotrimerization of phenylacetylene to form
1,2,4- and 1,3,5-triphenylbenzene. Finally, within each group of amines, hydroamination
proceeded at a higher rate with amines possessing the highest pKb values, or in other
words the lowest basicity (Figure 33).296 This observation was contrary to that observed
161 using other late metal catalysts.107 The nature of these trends remain an area of active pursuit in the Schmidt group.
Table 24. Hydroamination of phenylacetylenea
b c Entry Amine pKb Product Yield[%]
1 Aniline 9.37 75 Ph N
2 p-Toluidine 8.92 67 Ph N
3 Benzylamine 4.67 Ph N 12
4 Cyclohexylamine 3.34 6 Ph N
5 Morpholine 5.67 Ph N 62 O
6 Piperidine 2.88 Ph N 38
aReaction conditions: 6.0 mmol of phenylacetylene, 0.60 mmol of
amine, 0.030 mmol 11a, 70°C, THF, 22 h. bRef. 297. cDetermined by
average of 2 GC runs.
162 1.2 R2 = 0.986 1
0.8
0.6
0.4
0.2 Catalyst Activity (1/(M*hr)) 0 345678910
Amine pKb
Figure 33. Effect of amine pKb on catalyst activity of 11a towards hydroamination.
Buchwald-Hartwig Coupling (Aryl Amination)
Indoles are an important class of substrates, not only of academic interest, but also
found throughout the pharmaceutical industry. One means of synthesizing indoles is
through aryl amination of a di-substituted aryl halide with an allyl amine, followed by a
subsequent intramolecular Heck coupling.297 Therefore, one of the targeted classes of aryl amination products comprises those that result from the coupling of aryl halides with anilines containing halogenated substituents. In order to demonstrate the versatility of the 3-iminophosphine ligand series, aryl amination using ligated palladium(II) chloride complexes was investigated (Scheme 28).
In order to minimize false positives, each catalytic run of twelve vials included two control vials. One control vial contained a duplicate of one of the new experiments, while the other vial was composed of reagents identical to a previous catalytic run.
cat., base, Ar X + H2NR Ar NHR + HX
Scheme 28. General reaction of primary amines with aryl halides.
163 Furthermore, the reported conversion percentages were an average of three independent
measurements. These measurements are the ratios of the internal standard peak, the aryl
halide peak, and finally the amine peak to the product peak. Outliers (± 10%) were
discarded. Moreover, each of the aforementioned peaks was the average to two GC runs,
whose outliers (± 5%) were discarded. Final products were confirmed by 1H and 13C
NMR spectroscopy, when possible.
Since secondary amines are more basic than primary amines,296 permitting for a
stronger interaction between the metal and the nitrogen, they were investigated as the
initial amine source. The coupling of either bromobenzene or p-bromotoluene readily
proceeds with a large array of secondary amines with only 1 mol% catalyst loading of 9a
and sodium tert-butoxide as the base (Table 25). Entries 1-10 clearly demonstrate that catalytic activity for a wide range of amines was greater for bromobenzene than for p-
bromotoluene. Moreover, when an aromatic ring was used in place of a cyclohexyl group
(entries 7-10), a higher yield was observed. One explanation might be that the aromatic
ring affords added stability to the likely palladium-amido catalytic intermediate (Scheme
13). Another observed trend was the relationship of catalytic activity to boiling point.
When the reaction temperature was above the least reactive amines’ boiling points
(entries 1-4), the reaction kinetics were slower since less amine was present in the
solution phase. Generally speaking, the longer the reaction time, the higher the
conversion that was observed, although the conversion was found to generally quit increasing after 72-120 hours.
From its initial success with secondary amines, it was believed that bromobenzene would be a good aryl halide candidate to investigate the reactivity of substituted primary
164 Table 25. Aryl amination of secondary amines with bromobenzene
and bromotoluenea
Br cat., base, + HNRR' Ar NRR' + HBr Y
Entry Amine Y Yield[%]b
d 1 NH H 55 (57) d 2 CH3 26 (26) 3 H 30 (43)d n HN(Me) Bu d 4 CH3 6 (15)
5 n H c HN Bu2 56 (56) d 6 CH3 47 (59) 7 H 92 (92)d HN(CH Ph) 2 2 d 8 CH3 85 (85) 9 H 73 (76)d HNCy 2 d 10 CH3 66 (69) 11 H 88 (96)d HN(Cy)Ph d 12 CH3 83 (90)
c 13 NH H 99 (99)
c 14 O NH H 57 (61)
aReaction conditions: 1 mmol aryl bromide, 1.2 mmol amine, 1
mol% 9a, 2 mL toluene, 1.4 mmol NaOtBu, 110°C. bAverage of 2
GC runs after 24 h. cAfter 72 h. dAfter 120 h.
anilines (Table 26). Entries 1-4 demonstrate that the nature of electron donation from the para position of the aniline ring was important, although a general trend was unattainable because alkyl substitution both increased (entry 4) and decreased (entry 2) product conversion, while incorporation of a trifluoromethoxy substituent completely shut down
165 the reaction. Dimethyl substitution at the 4- and 5-positions was detrimental to the
observed catalytic activity (entry 5). Moreover, fluoro or iodo substitution hindered the reactivity in all cases, as observed in entries 7-10, and the incorporation of a bromo substituent at the 2-position almost completely stopped catalysis from occurring (entry 6).
However, chloro substitution was beneficial with respect to fluoro substitution as observed by a comparison of entries 7, 10-11, and 18. When a meta chloro group was the only substituent on the aromatic ring, an increase in reactivity was observed as evident by a comparison of entries 1 and 11. Entries 12-15 show that the incorporation of mono- or di-alkyl ortho substitution increased the activity of the catalyst significantly, which can be explained by the increased electron density in the aromatic ring due to the electron donating alkyl groups at the ortho positions. Also, the bulkiness of the alkyl groups at the ortho positions may lead to a more stable palladium-amido intermediate, enhancing the catalytic activity by sterically shielding the palladium center from decomposition.
Another class of substrates was those which were substituted at the 2- and 5-positions
(entries 7 and 17-18). When a methyl was present at the 5-position, a methoxy at the 2- position displayed the highest reactivity, followed by a chloro substituent and then the least reactive fluoro derivative. Finally, chloro substitution at the 3-position (entry 11) resulted in the highest activity, followed by methoxy, alkyl, and fluoro substitutions
(entries 10 and 19-20).
To further extend catalyst utility, di-halo substituted anilines, as well as a few alkyl amines, were used as the amine reactants (Table 27). Similar to the synthesis of indoles, a di-halo substituted aniline would allow for a further cross-coupling reaction to occur, leading to the incorporation of multiple fragments. Entries 1-6 show that 9a
166 Table 26. Aryl amination of substituted primary anilines with bromobenzenea
Entry Amine Yield[%]b Entry Amine Yield[%]b
NH2 Cl NH2 1 9 (15)c 11 34 (41)c
NH2 Me c c 2 6 (11) 12 NH2 81 (95) tBu Me
NH2 Et c c 3 0 (0) 13 NH2 73 (99) F3CO Et i NH2 Pr 4 64 (64)c 14 88 (95)c NH2 Me iPr
Me NH2 NH2 5 12 (31)c 15 88 (90)c Me iPr
NH2 Me c c 6 3 (3) 16 NH2 29 (50) Me Br Cl
Me NH2 Me NH2 7 1 (6)c 17 65 (82)c F OMe
NH2 Me NH2 8 1 (6)c 18 29 (55)c F Cl
NH2 MeO NH2 9 0 (0) c 19 11 (19)c I
F NH2 Et NH2 10 3 (8)c 20 9 (35)c a Reaction conditions: 1 mmol bromobenzene, 1.2 mmol amine, 1 mol% 9a, 2 mL toluene, 1.4 mmol NaOtBu, 110°C. bAverage of 2 GC runs after 24 h. cAfter 72 h.
167 Table 27. Aryl amination of primary amines with bromobenzenea
Entry Amine Yield[%]b Entry Amine Yield[%]b
Cl Br NH2 c c 1 Cl NH2 52 (52) 6 44 (44) Br
Cl NH2 Me NH2 2 33 (33)c 7 32 (32)c Cl Br
Cl NH2 NH 3 26 (37)c 8 2 25 (32)c
Cl
Cl NH2 4 3 (7)c 9 NH2 6 (15)c
Cl
Cl NH2 c c 5 43 (43) 10 NH2 15 (21)
Cl Cl
aReaction conditions: 1 mmol bromobenzene, 1.2 mmol amine, 1 mol% 9a, 2 mL
toluene, 1.4 mmol NaOtBu, 110°C. bAverage of 2 GC runs after 24 h. cAfter 72 h. displays moderate activity for the aryl amination of several di-halogenated anilines. Only entry 4 displayed very poor turnover numbers in relation to the other substrates; however, the di-bromo analog displayed reasonably good reactivity. Therefore, the overall effect of halogen substitution at the 2-position remains unclear. By replacing the methyl at the
4-position with a bromo substituent, the reactivity was almost increased 3 fold (Table 26 entry 5, Table 27 entry 7). Entries 8-10 display the reactivity of some primary alkyl amines with bromobenzene. The low catalytic activity was attributed to instability in the palladium-amido intermediate (entries 8-10). In entry 10, the low conversion may also
168 be an effect of the lack of amine present in solution at the reaction temperature. In
general, alkyl substitution of the aryl amines at the 2- and 6-positions showed the highest
catalytic activity, although reactivity is diminished by further substitution of the arene.
The reactivity of aryl amines which are substituted at the 4-position is highly dependent
upon the nature of the substituent. Typically, fluoro, bromo, and iodo substitution was
disadvantageous while chloro substitution was favorable. To better grasp the substitution
effect at the meta and para positions, a Hammett plot was constructed (Figure 34).298 For
di-substituted aryl amines, a sum of Hammett constants was used. In general, anilines
having small or negative Hammett constants were less reactive than those with large
positive values (x ≥ 0.15).
Even though bromobenzene served as a sufficient probe of the catalytic activity of
9a with various amines, further investigation was undertaken to see if similar trends were
observed upon varying the aryl halide and therefore, halobenzonitriles were investigated
(Table 28). Since chlorobenzonitrile displayed no reactivity while its bromo analog did,
100
80
60
% Yield 40
20
0 -0.4 -0.2 0 0.2 0.4 0.6 0.8 Sum of Hammett Substituent Constants
Figure 34. Effect of aniline substitution on aryl amination.
169 Table 28. Aryl amination with halobenzonitrilesa
X cat., base, + HNRR' Ar NRR' + HX NC
Entry X Amine Yield[%]b
1 Cl Di-nbutylamine 0 (0)c 2 Br Di-nbutylamine 34 (53)c 3 Br m-Anisidine 0 (0)c 4 Br Piperidine 57 (59)c 5 Br Morpholine 52 (58)c 6 Br Cyclohexylamine 4 (57)c
aReaction conditions: 1 mmol aryl halide, 1.2 mmol amine, 1
mol% 9a, 2 mL toluene, 1.4 mmol NaOtBu, 110°C.
bDetermined by the average of 2 GC runs after 24 h. cAfter
120 h. bromobenzonitrile was chosen to screen a small series of amines. Entries 2-6 show the proficiency of 9a with the selected amines and clearly indicate once again that the most efficient amines were the secondary amines. Moreover, a comparison of these bromobenzonitrile entries to the analogous reactions with bromobenzene reveals that having a hydrogen rather than a nitrile group increases product yield (Table 25: entries
11-13; Table 26: entry 19; and Table 27: entry 9).
Not only is the nature of the amine important, but the substituents on the aryl halide are also a key factor in aryl amination catalytic activity. Therefore, to better grasp the substrate tolerance of 9a, a series of para substituted aryl halides were screened for this reaction. Entries 1-5 show that the more electron donating substituents had higher reactivity (Table 29). Iodobenzene was slightly more reactive over a longer period of
170 Table 29. Aryl amination with para-substituted aryl halidesa
X n cat., base, n + HN Bu2 Ar Bu2 + HX Y
Entry X Y Yield[%]b
1 Br CN 34 (56)c c 2 Br NO2 6 (47) c 3 Br OCH3 41 (45) c 4 Br CH3 47 (59) 5 Br H 56 (56)c 6 I H 41 (69)c 7 Cl H 0 (0)c c 8 Cl CH2CHO 0 (0) c 9 Cl COCH3 0 (0) c 10 Cl NO2 13 (17)
aReaction conditions: 1 mmol aryl halide, 1.2 mmol di-n-
butylamine, 1 mol% 9a, 2 mL toluene, 1.4 mmol NaOtBu, 110°C.
bDetermined by the average of 2 GC runs after 24 h. cAfter 168 h.
time than bromobenzene, while chlorobenzene was almost completely unreactive. Only
4-nitro-1-chlorobenzene displayed any reactivity in the chlorobenzene series (entries 7-
10).
In order to have a broader substrate scope, a variety of other aryl halides were
reacted with di-n-butylamine (Table 30). In general, very minor changes in the nature of the aryl halide had significant effects. Most notably, entries 3-4, in which the only difference was the location of the bromo substituent in relation to the nitrogen of the pyridinyl ring, had very different results. This can be attributed to the weaker carbon-
171 bromine bond in 2-bromopyridine due to the electronegativity of the nitrogen atom.
Additionally, mesityl bromide was unreactive (entry 5), most likely due to steric hindrance caused by the methyl substituents at the 2- and 6-positions. 2-Ethyl-
Table 30. Aryl amination with di-n-butylaminea
n cat., base, n Ar X +HNBu2 Ar N Bu2 + HX
Entry Aryl halide Yield[%]b Entry Aryl halide Yield[%]b
Br Br 1 56 (56)c 6 34 (53)d
Me Br Cl 2 33 (51)d 7 0 (0)d OMe Br Cl 3 2 (19)d 8 10 (79)d N Et Br Cl 4 96 (96)d 9 0 (0)d N CH2CHO
Me I d 5 Br 0 (0)d 10 0 (0) OH Me Me
aReaction conditions: 1 mmol aryl halide, 1.2 mmol di-n-butylamine , 1 mol% 9a, 2
mL toluene, 1.4 mmol NaOtBu, 110°C. bDetermined by the average of 2 GC runs
after 24 h. cAfter 72 h. dAfter 168 h. chlorobenzene (entry 8) was substantially more reactive than the unsubstituted chloro analog (Table 29: entry 7), while the effect of methoxy substitution at the ortho position was negligible. Aryl halides with aldehyde or hydroxy groups were unreactive, most likely due to lack of solubility in the reaction media (entries 9-10).
172 For substituted aryl halides, bromides were generally superior to chlorides and
iodides. While electron donating groups such as alkyl or methoxy reduced catalytic
activity with respect to the unsubstituted aryl halide, electron withdrawing groups greatly
hindered reactivity. To illustrate the effect meta and para substitution has on product yield, a Hammett plot was constructed (Figure 35).298 From this graph, it is clear that
substituted aryl bromides with negative Hammett constants displayed the highest
reactivity. Furthermore, bromo substitution was more favorable than chloro or iodo in
most cases.
In summary, aryl amination was observed for a wide array of amines and aryl
halides. Secondary amines generally displayed a higher reactivity, followed by
substituted anilines and then primary amines. Additionally, the nature of the substituents,
as well as the location of the substituents with respect to each other and the nitrogen
atom, played a vital role in the reaction rate. Similarly, substituents on the aryl halide
impacted catalyst activity. The most obvious trend was that bromo arenes were more
reactive than chloro arenes, which were almost completely unreactive.
100
80
60 Bromo Iodo
% Yield 40 Chloro
20
0 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 Sum of Hammett Substituent Constants
Figure 35. Effect of aryl halide substitution on aryl amination.
173 Suzuki Cross-Coupling
The importance of biaryls in the chemical industry is undeniable, as they are found throughout natural products, pharmaceuticals and polymers.188 Also, the introduction of biaryls within a cascade reaction allows for the generation of some unique and possibly useful structural motifs. Therefore, a series of boronic acids and aryl halides were screened as possible substrates for Suzuki cross-coupling in the presence of 9a
(Table 31). Nitrile substitution on the aryl bromide completely prohibits cross-coupling with all boronic acids tested (entries 4, 8, and 12). The use of unsubstituted aryl groups
Table 31. Suzuki coupling of boronic acids with aryl halidesa
Br B(OH)2 cat., base, + Ar Ar + BrB(OH)2 Y Z
Entry Y Z Yield[%]b
1 H H 85
2 CH3 H 99
3 OCH3 H 77 4 CN H 0
5 H CH3 76
6 CH3 CH3 76
7 OCH3 CH3 99
8 CN CH3 0
9 H OCH3 99
10 CH3 OCH3 99
11 OCH3 OCH3 99
12 CN OCH3 0
a Reaction conditions: 1.5 mmol boronic acid, 1 mmol aryl bromide, 2 mL
b solvent, 3 mmol K3PO4, 110°C, 24 h. Isolated yields.
174 or those with methyl or methoxy groups all showed excellent reactivity (entries 1-3, 5-7,
9-11), while the use of p-methoxy boronic acids proceeded almost quantitatively (entries
9-11). Although more experiments would be useful to establish the general trends, it was
clear that one of the determining factors in the rate of biaryl formation was the electron-
donating ability of the para substituent on the boronic acid.
Other factors that could influence biaryl formation include the reaction media as
well as the type of base present. Therefore, to elucidate the most favorable reaction conditions, a series of reactions were investigated with p-bromotoluene and anisole boronic acid as the substrates, 9a as the catalyst, and a reaction time of 4 hours (Table
32). Entries 1-5 display the effect of various bases on biaryl formation and clearly, both alkali butoxides were unreactive, which was mainly attributed to lack of solubility.
Furthermore, potassium carbonate (entry 4) was the most proficient base, while cesium carbonate was far inferior (entry 1). Entries 5-6 reveal that by increasing the temperature of the reaction, the product yield increased, however it remained ambiguous whether this was due to faster kinetics or improvements in solubility. The solvent dependence was also investigated (entries 7-12) and it was found that dimethoxyethane produced the highest biaryl yield, although the overall solvent effects were rather minor.
To summarize the Suzuki cross-coupling results, catalyst 9a successfully converted several boronic acids to the corresponding biaryls with a variety of aryl halides. Also, a variety of bases may be used to facilitate the cross-coupling, however butoxides should be avoided. Another important observation was that Suzuki coupling can be carried out successfully in a variety of solvents. Finally, changing the boronic acid or the aryl halide often has significant effects on the catalytic activity. Therefore,
175 Table 32. Suzuki coupling in the presence of different bases and solventsa
Br B(OH)2 cat., base + Ar Ar + BrB(OH)2 Me MeO
Entry Base Solvent Yield[%]b
1 Cs2CO3 Toluene 49 2 KOtBu Toluene 0 3 NaOtBu Toluene 0
4 K2CO3 Toluene 92
5 K3PO4 Toluene 76 c 6 K3PO4 Toluene 83
7 K3PO4 Tetrahydrofuran 82
8 K3PO4 Dioxane 71
9 K3PO4 Acetonitrile 77
10 K3PO4 Dimethoxyethane 91
11 K3PO4 Methanol 85
12 K3PO4 Ethanol 69
aReaction conditions: 1.5 mmol anisole boronic acid, 1 mmol p-
bromotoluene, 2 mL solvent, 3 mmol base, 25°C, 4 h. bIsolated yields.
cReaction temperature was 110°C. the reaction conditions outlined were only true for the aforementioned reactions with 9a, and a set of general reaction conditions remains elusive.
IV-3: Experimental Methods
General Considerations. CDCl3 was purchased from Cambridge Isotope Laboratories.
Toluene, tetrahydrofuran, methanol, ethanol, dimethoxyethane, dioxane, ethyl acetate, hexanes, chloroform, methylene chloride, magnesium, hydrochloric acid, and acetonitrile were purchased from Fisher and used without further purification. Trimethylborate,
176 aniline, p-toluidine, 4-(trifluoromethoxy)aniline, 2-bromo-4-methylaniline, 2-fluoro-5-
methylaniline, 3,4-dimethylaniline, 2-fluoroaniline, 2-iodoaniline, 3-fluoroaniline, 3-
chloroaniline, 2-isopropylaniline, 4-chloro-2-methylaniline, 2-methoxy-5-methylaniline,
2-chloro-5-methylaniline, m-anisidine, 3-ethylaniline, 2,5-dichloroaniline, 3,4-
dichloroaniline, 2,3-dichloroaniline, 3,5-dichloroaniline, 2,4,5-trichloroaniline, 4-bromo-
3-methylaniline, 1-bromo-2,4,6-trimethylbenzene, cyclohexylamine, pyrrolidine, N-
cyclohexylaniline, dibenzylamine, N-methyl-n-butylamine, dicyclohexylamine,
piperidine, morpholine, di-n-butylamine, tert-butylamine, aniline, 2,6-dimethylaniline,
2,6-diethylaniline, 2,6-diisopropylaniline, 4-tert-butylaniline, benzylamine, 4-
bromobenzonitrile, 4-chlorobenzonitrile, p-bromotoluene, m-bromotoluene, p-
bromoanisole, 4-nitro-bromobenzene, 4-chlorobenzaldehyde, 4-chloroacetophenone, 4-
nitro-chlorobenzene, chlorobenzene, iodobenzene, 2-bromopyridine, 3-bromopyridine, 1- bromonapthalene, 2-chloroanisole, 2-chloroethylbenzene, 3-chlorobenzaldehyde, and 2-
iodophenol were purchased from Acros/Aldrich and used without further purification for
aryl amination and Suzuki cross-coupling reactions. For hydroamination reactions,
methylene chloride, toluene, and tetrahydrofuran were purified by passage through a
column of activated 4Å molecular sieves and degassed with nitrogen prior to use. 1,4-
Dioxane was refluxed over sodium and distilled under nitrogen. Piperidine, p-toluidine,
aniline, benzylamine, and cyclohexylamine were dried by vacuum transfer or distillation
from calcium hydride. Morpholine was purified by distillation from sodium. 1,3-
Cyclohexadiene was vacuum transferred from sodium borohydride. Phenylacetylene was purified by passage through a column of alumina, and further vacuum transferred from calcuim hydride. 1H and 13C NMR data were obtained on a 600 MHz Inova NMR
177 spectrometer at ambient temperature at 599.9 and 150.9 MHz, respectively. 1H NMR
13 shifts are given relative to CHCl3 (7.26 ppm) and C NMR shifts are given relative to
CDCl3 (77.3 ppm), except for Suzuki coupling products which were referenced to TMS.
Gas chromatography was performed on a Varian CP-3800 gas chromatograph equipped
with an FID detector. Aryl boronic acids were prepared according to literature.299
General Procedure for Hydroamination of Cyclohexadiene: 1,3-Cyclohexadiene (3.6 mmol), amine (0.60 mmol), and 1.0 mL of methylene chloride was added to 11a (0.030 mmol) in a teflon capped 4 mL scintillation vial in a dry box. After heating to 50°C for
22 hours, 100 μL of dodecane was added to the reaction vial as an internal standard and product yield was determined via gas chromatography. Hydroamination products were readily isolated by column chromatography (silica gel) and removal of solvent via rotary evaporation. 1H and 13C NMR were obtained and compared to literature values.107
General Procedure for Hydroamination of Phenylacetylene: Phenylacetylene (6.0 mmol), amine (0.60 mmol), and 1.0 mL of tetrahydrofuran was added to 11a (0.030 mmol) in a teflon capped 4 mL scintillation vial in a dry box. After heating to 70°C for
22 hours, 100 μL of dodecane was added to the reaction vial as an internal standard and product yield was determined via gas chromatography. Hydroamination products were readily isolated by column chromatography (silica gel) and removal of solvent via rotary evaporation. 1H and 13C NMR were obtained and compared to literature values.300-302
Gas chromatography standards (Table 5: entries 1-4) were synthesized by a general procedure outlined by Bäckvall.303
178 General Procedure for Aryl Amination: A teflon capped 4 mL scintillation vial was
charged with 9a (0.01 mmol) in a dry box. Sodium tert-butoxide (1.40 mmol) was added
to the vial. Aryl bromide (1.00 mmol), amine (1.20 mmol) and toluene (2 mL) were mixed thoroughly and added to the scintillation vial, which was heated to 110°C for 24
hours, unless otherwise noted. 10 μL of dodecane was added to the reaction vial as an
internal standard and product yield was determined via gas chromatography. Products
were isolated by column chromatography (silica gel) and removal of solvent by rotary
evaporation. 1H and 13C NMR spectra were obtained and compared to literature values when applicable.186, 304-326
N-(4-Chloro-2-methylphenyl)aniline (Table 26 Entry 16): yellow liquid (50%); 1H
3 3 3 NMR (600 MHz) δ 7.38 (d, JHH = 7.8 Hz, 1H), 7.19 (t, JHH = 7.2 Hz, 2H), 7.05 (d, JHH
3 3 = 7.2 Hz, 2H), 7.02 (s, 1H), 6.83 (t, JHH = 7.2 Hz, 1H), 6.75 (d, JHH = 7.8 Hz, 1H), 3.42
(s, 1H), 2.19 (s, 3H); 13C{1H} NMR δ 145.4, 140.2, 137.7, 137.0, 130.8, 129.0, 122.4,
117.4, 116.9, 111.0, 21.1.
N-(2-Chloro-5-methylphenyl)aniline (Table 26 Entry 18): yellow liquid (55%); 1H
3 3 NMR (600 MHz) δ 7.21 (t, JHH = 7.2 Hz, 2H), 7.05 (s, 1H), 7.00 (d, JHH = 7.2 Hz, 2H),
3 3 3 6.93 (d, JHH = 7.8 Hz, 1H), 6.86 (t, JHH = 7.2 Hz, 1H), 6.34 (d, JHH = 7.8 Hz, 1H), 3.41
(s, 1H), 2.22 (s, 3H); 13C{1H} NMR δ 146.7, 141.9, 131.0, 129.6, 129.3, 127.1, l23.7,
120.9, 116.6, 108.9, 18.1.
N-(2,3-Dichlorophenyl)aniline (Table 27 Entry 1): yellow liquid (52%); 1H NMR (600
3 3 3 MHz) δ 7.43 (t, JHH = 7.8 Hz, 1H), 7.19 (t, JHH = 7.2 Hz, 2H), 7.02 (d, JHH = 7.2 Hz,
3 3 3 2H), 6.99 (t, JHH = 7.8 Hz, 1H), 6.85 (d, JHH = 7.2 Hz, 1H), 6.68 (d, JHH = 7.8 Hz, 1H),
179 3.52 (s, 1H); 13C{1H} NMR δ 145.0, 140.4, 136.4, 129.4, 129.1, 127.6, 122.4, 121.8,
117.9, 117.4.
N-(2,4,5-Trichlorophenyl)aniline (Table 27 Entry 5): yellow liquid (43%) 1H NMR
3 3 (600 MHz) δ 7.78 (s, 1H), 7.23 (s, 1H), 7.19 (t, JHH = 7.2 Hz, 2H), 7.02 (d, JHH = 7.2
3 13 1 Hz, 2H), 6.86 (t, JHH = 7.2 Hz, 1H), 3.41 (s, 1H); C{ H} NMR δ 143.2, 143.1, 132.4,
132.3, 129.1, 127.8, 123.6, 122.7, 121.7, 117.9.
N-(2,5-Dibromophenyl)aniline (Table 27 Entry 6): yellow liquid (44%); 1H NMR
3 3 (600 MHz) δ 7.28 (t, JHH = 7.2 Hz, 2H), 7.24 (s, 1H), 7.08 (d, JHH = 7.2 Hz, 2H), 7.07
3 3 3 (d, JHH = 7.8 Hz, 1H), 7.00 (d, JHH = 7.8 Hz, 1H), 6.87 (t, JHH = 7.2 Hz, 1H), 3.38 (s,
1H); 13C{1H} NMR δ 143.9, 137.3, 134.3, 129.3, 127.3, 122.4, 121.9, 119.4, 117.9,
111.5.
N-(4-Bromo-3-methylphenyl)aniline (Table 27 Entry 7): yellow liquid (32%); 1H
3 3 3 NMR (600 MHz) δ 7.22 (t, JHH = 7.2 Hz, 2H), 6.99 (d, JHH = 7.8 Hz, 1H), 6.864 (d, JHH
3 3 = 7.2 Hz, 2H), 6.857 (s, 1H), 6.84 (t, JHH = 7.2 Hz, 1H), 6.56 (d, JHH = 7.8 Hz, 1H), 3.38
(s, 1H), 2.36 (s, 3H); 13C{1H} NMR δ 145.9, 143.1, 137.7, 132.1, 129.4, 121.4, 118.0,
117.2, 116.9, 115.0, 22.7.
4-Nitrophenyl-di-n-butylamine (Table 29 Entry 10): yellow liquid (17%); 1H NMR
3 3 3 (600 MHz) δ 7.85 (d, JHH = 8.4 Hz, 2H), 7.10 (d, JHH = 8.4 Hz, 2H), 3.05 (t, JHH = 7.2
3 13 1 Hz, 4H), 1.22-1.30 (m, 8H), 0.85 (t, JHH = 7.2 Hz, 6H); C{ H} NMR δ 153.1, 137.5,
125.7, 116.0, 50.8, 30.1, 20.4, 12.3.
General Procedure for Suzuki Cross-Coupling: A teflon capped 4 mL scintillation
vial was charged with 9a (0.01 mmol) in a dry box. Base (3.00 mmol) and boronic acid
(1.500 mmol) were added to the reaction vial. Aryl bromide (1.00 mmol) and reaction
180 solvent (2 mL) were mixed thoroughly and added to the scintillation vial, which was heated to 110°C for 24 hours, unless otherwise noted. Products were isolated by column chromatography (silica gel) and removal of solvent by rotary evaporation. 1H and 13C
NMR spectra were obtained and compared to literature values when applicable.327-330
Table 33. Gas Chromatography Collection Parameters
Hydroamination Aryl Amination
Volume 5.0 μL 5.0 μL
Temperature 200°C 200°C Injector Split events Inital On 20 Initial Off 20 setup 0.00 min Off 20 0.75 min On 20 EFC Pressure 10.0 Psi 10.0 Psi
Carrier gas N Column 2 N2 setup Length 30.00 m 30.00 m Inside diameter 320 μm 320 μm
Type FID FID Detector Temperature 250°C 250°C setup N2 flow rate 30 mL/min 30 mL/min H2 flow rate 30 mL/min 30 mL/min Air flow rate 300 mL/min 300 mL/min
Injection mode Std (Split/Splitless) Std (Split/Splitless)
Depth 90% 90% Autosampler Pre-injection setup 3 3 washes Post-injection 3 3 washes
Event T Hold Rate T Hold Rate
Initial 50 1.20 n/a 50 1.00 n/a
1st event 70 0.30 80 140 10.00 5
2nd event 60 0.20 80 180 22.22 10 Oven setup 3rd event 90 1.00 30 4th event 120 2.00 10 5th event 150 2.50 12 6th event 180 19.55 80
181 IV-4: Conclusion
3-Iminophosphine ligated palladium(II) complex 11a was a moderately active
catalyst for the intermolecular hydroamination of 1,3-cyclohexadiene and phenylacetylene. The dichloride, 9a, was an efficient catalyst for aryl amination and
Suzuki cross-coupling for a wide range of aryl halides. The general trend in aryl
amination was that secondary amines were substantially more reactive than their primary
counterparts. Also, an array of halogenated anilines was coupled with bromobenzene,
which composed the first step in the one-pot synthesis of indoles. The implementation of
Suzuki coupling demonstrated that 9a may be used for more than just aryl amination
reactions, which increases the ability of 3-iminophosphines to serve as a general ligand
set for a variety of catalytic transformations.
182
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217
Appendix 1:
──────────────────────────────
Table of Compounds
──────────────────────────────
218 Cl Cl t Cl Me Ph O Bu O Ph O
1a 1b 1c
Cl Cl O O
1d 1e
Cl Cl Cl Me Ph N R tBu N R Ph N R R = tBu (2a) R = tBu (2f) R = tBu (2k) Ph (2b) Ph (2g) Ph (2l) 2,6-Me2Ph (2c) 2,6-Me2Ph (2h) 2,6-Me2Ph (2m) 2,6-Et2Ph (2d) 2,6-Et2Ph (2i) 2,6-Et2Ph (2n) i i i 2,6- Pr2Ph (2e) 2,6- Pr2Ph (2j) 2,6- Pr2Ph (2o)
Cl Cl N R N R
R = tBu (2p) R = tBu (2v) 2,6-Me2Ph (2q) 2,6-Me2Ph (2w) 2,6-Et2Ph (2r) 2,6-Et2Ph (2x) i i 2,6- Pr2Ph (2s) 2,6- Pr2Ph (2y) t 4- BuPh (2t) CH2Ph (2z) CH2Ph (2u)
219 Ph Ph R Ph Ph P Ph PN Ph PMe tBu Ph N Ph N R R R = tBu (3a) R = tBu (3f) R = tBu (3k) Ph (3b) Ph (3l) 2,6-Me2Ph (3c) 2,6-Me2Ph (3h) 2,6-Me2Ph (3m) 2,6-Et2Ph (3d) 2,6-Et2Ph (3i) 2,6-Et2Ph (3n) i i i 2,6- Pr2Ph (3e) 2,6- Pr2Ph (3j) 2,6- Pr2Ph (3o)
Ph R PR'2 PR'2 Ph PN N R N R
Ph
R = 2,6-Et2Ph (3d) R’ = Ph R’ = Ph R = tBu (3p) R = tBu (3v) 2,6-Me2Ph (3q) 2,6-Me2Ph (3w) 2,6-Et2Ph (3r) 2,6-Et2Ph (3x) i i 2,6- Pr2Ph (3s) 2,6- Pr2Ph (3y) t 4- BuPh (3t) CH2Ph (3z) CH2Ph (3u)
R’ = tBu R = tBu (3aa)
Ph3P Ph Ph Cl Cl Pd Ph NH Ph 2 Ph P P Pd tBu Cl 3 Et Ph N NPh NPh Et
4 5 7
220 Ph tBu Ph Ph Cl Ph Pd P P Cl Cl Pd Ph NAr N Cl tBu
Ar = Ph (8a) 8c 2,6-Me2Ph (8b)
t Ph Ph t Ph Ph Bu Bu P Cl P Cl P Cl Pd Pd Pd N Cl N Cl N Cl R R tBu R = tBu (9a) R = tBu (9h) 9m 2,6-Me2Ph (9c) 2,6-Me2Ph (9i) 2,6-Et2Ph (9d) 2,6-Et2Ph (9j) i i 2,6- Pr2Ph (9e) 2,6- Pr2Ph (9k) t 4- BuPh (9f) CH2Ph (9l) CH2Ph (9g)
Ph Ph Ph Ph P + P - Pd Pd [Y] tBu N Cl N tBu
10a Y = OTf (11a) B(C6F5)4 (11b) PF6 (11c)
221 Ph Ph P Cl Pd t Bu N Cl NHRR'
t HNRR’ = HN(CH2CH3)2 (12a) H2N Bu (12g) i HN(CH2CH2)2O (12b) HN Pr2 (12h) HN(C5H10) (12c) H2NC6H11 (12i) n t HN(Me) Bu (12d) H2N Bu (12j) n HN Bu2 (12e) H2N-p-CH3C6H4 (12k) HN(CH2C6H5)2 (12f) H2NCH2C6H5 (12l)
2+ Ph Ph tBu Ph Ph X P N - P OTf . 2 [OTf] Pd Pd Pd N P N OTf t X t Bu Ph Ph Bu X = Cl (13a) 14 Br (13b)
t Ph Ph Ph Bu Ph P Br Me N P Me Pd Pd Pd N Cl t Me Br P tBu Bu N Ph Ph
X = Cl (15a) 15b’ Br (15b) Ph Ph P Me Pd N OTf tBu
16
222
Appendix 2:
──────────────────────────────
Modified Literature Preparations
──────────────────────────────
223 A2-1. Bis(1,5-cyclooctadiene)nickel(0): Ni(COD)2
The synthesis of bis(1,5-cyclooctadiene)nickel(0) was performed using a
modified procedure.254 Anhydrous nickel(II) acetylacetonate and tetrahydrofuran were
added to a Schlenk flask. 1,5-Cyclooctadiene (9.0 mL, 7.3 mmol) was added to the flask
and the solution was cooled to -78°C. The solution was treated with
diisobutylaluminumhydride (45.4 mL, 45.5 mmol) and the solution was warmed to 0°C.
The product was precipitated out using 65 mL of diethyl ether and to maximize
precipitation, the reaction was cooled to -78°C overnight. After the solution was
decanted, the yellow solid was washed with diethyl ether until the brown residue is no
longer visible. The yellow solid was dried under vacuum at 0°C.
A2-2. Tetrakis(triphenylphosphine)nickel(0): Ni(PPh3)4
The synthesis of tertrakis(triphenylphosphine)nickel(0) was accomplished by two
distinct methods.255 In the first, a flask was charged with bis(1,5-
cyclooctadiene)nickel(0) (0.500 g, 1.82 mmol) and triphenylphosphine (1.91 g, 7.27
mmol). 30 mL of pentane was added to the flask and stirred at 0°C for 1 hour. The
solution was filtered, and the solid was washed with an additional 20 mL of pentane. The
red-brown solid was dried under vacuum. For the second method, a flask was charged
with anhydrous nickel(II) acetylacetonate (0.500 g, 1.95 mmol) and triphenylphosphine
(2.04 g, 7.79 mmol). 15 mL of tetrahydrofuran was added to the flask and the solution
was cooled to 0°C for 10 minutes. Diisobutylaluminiumhydride (4.9 mL, 4.9 mmol) was
added to the flask, which was then gradually warmed to 0°C. The product was precipitated using 60 mL of diethyl ether and cooled overnight at -78°C to maximize
224 precipitation. The solution was cold-filtered and the resulting solid was washed with
pentane (3 x 20 mL) and dried in vacuo.
A2-3. Sodium diphenylphosphide: NaPPh2
The synthesis of sodium diphenylphosphide was accomplished by using a
modified literature procedure.252 A flask is charged with sodium metal (3.82 g, 166
mmol) and 150 mL of 1,4-dioxane. Diphenylchlorophosphine (7.4 mL, 40 mmol) is
added and the mixture is heated to reflux for 7 hours. 100 mL of tetrahydrofuran is added
to aid in the precipitation of the sodium metal. The orange slurry is cooled to ambient
temperature and then filtered through a frit to remove unreacted sodium.
A2-4. Lithium diphenylphosphide: LiPPh2
Lithium diphenylphosphide was synthesized by two distinct methods.253 In the first, diphenylphosphine (1 equivalent) in pentane was reacted with a solution of n- butyllithium in hexanes (1.1 equivalents) at 0°C, allowing the reaction to warm to ambient temperature overnight. The solution was decanted, and the resulting yellow solid was washed with pentane (3 x 25 mL) and dried in vacuo. The second method utilizes diphenylchlorophosphine as the phosphorus starting material. A flask was charged with lithium aluminium hydride (2.5 equivalents) and diethyl ether. Slowly, diphenylchlorophosphine is added and stirred overnight, gradually warming the reaction to ambient temperature. Degassed water is added to the slurry, to neutralize unreacted lithium aluminium hydride. The solution is filtered into an addition funnel, which served as a separatory funnel. Once the aqueous layer is removed, the organic layer is washed with a 15% solution of sodium hydroxide and a second portion of degassed water. The organic layer was dried over magnesium sulfate, filtered, and cooled to 0°C. n-
225 Butyllithium (1.1 equivalents) was slowly added to the solution, which was stirred for an
additional 14 hours. The solution was decanted, and the resulting yellow solid was
washed with pentane (3 x 25 mL) and dried in vacuo.
A2-5. Diphenyl(trimethylsilyl)phosphine: Ph2PSiMe3
Diphenyl(trimethylsilyl)phosphine was readily formed using two methods.250 In the first, a flask was charged with lithium diphenylphosphide (0.515 g, 2.68 mmol) and
30 mL of pentane, which was cooled to 0°C for 5 minutes. Trimethylsilylchloride (0.37 mL, 2.9 mmol) was added to solution, which warmed to ambient temperature overnight.
The solution was passed through a pad of Celite and solvent removed, resulting in a yellow-tinted solution. The second method uses sodium diphenylphosphide as the phosphorus source. Once the sodium diphenylphosphide is formed, the slurry is distilled to remove the majority of the volatiles, leaving behind approximately 40 mL of solution.
The solution was placed in a water bath and trimethylsilylchloride (5.1 mL, 40 mmol) was added. 100 mL of pentane was added and the solution was passed through a pad of
Celite to remove sodium chloride. The solution was then distilled to removed the majority of the pentane, tetrahydrofuran and 1,4-dioxane, resulting in a yellow-tinted syrup.
A2-6. Aryl boronic acids: ArB(OH)2
The synthesis of aryl boronic acids was accomplished using a modified
procedure.299 Freshly polished magnesium ribbon was added to a Schlenk flask.
Tetrahydrofuran was added and the solution was stirred. Slowly, 1 mL of aryl halide was
added to the solution and initiated with iodine crystals, and allowed to stir for about 5
minutes or until the solution started to turn gray. The remainder of the aryl halide was
226 slowly added in 1 mL intervals. The reaction was heated to reflux for at least 4 hours.
The reaction was cooled to 0°C and trimethylborate was slowly added via syringe. The
reaction was warmed to ambient temperature and stirred for an additional 14 hours. A
solution of hydrochloric acid (10% by weight) was added until a pH = 1 was reached.
Diethyl ether was added the flask and the aqueous layer was removed. The organic layer
was washed with saturated sodium bicarbonate and sodium chloride solutions and was
then dried over magnesium sulfate. The organic layer was filtered and solvent was
removed, resulting in an off-white solid, which could be recrystallized from toluene.
A2-7. Tris(pentafluorophenyl)borane: B(C6F5)3
The synthesis of tris(pentafluorophenyl)borane was accomplished by using a
modified procedure.278 Bromopentafluorobenzene (3 equivalents) was added to Schlenk
flask containing pentane and was cooled to -78°C for 10 minutes. n-Butyllithium (3 equivalents) was added to the flask, which was stirred for 1 additional hour. NOTE:
Flask must remain cold, otherwise an explosion is likely. Also, large scale preparation should be performed in an explosion resistant hood or be enclosed in explosion resistant shield. Boron trichloride (1 equivalent) was slowly added via syringe, and the reaction was allowed to gradually warm to ambient temperature. The cloudy solution was then passed through a pad of Celite, resulting in a colorless solution. Solvent may be removed, resulting in the stable tris(pentafluorophenyl)borane as a off-white solid.
A2-8. Tetrakis(pentafluorophenyl)borate: LiB(C6F5)4
The synthesis of lithium tetrakis(pentafluorophenyl)borate was accomplished by
using a modified procedure.278 Bromopentafluorobenzene (1.1 equivalents) was added to
a Schlenk flask containing pentane and was cooled to -78°C for 10 minutes. n-
227 Butyllithium (1.1 equivalents) was added to the flask, which was stirred for 1 additional hour. A solution of tris(pentafluorophenyl)borane (1 equivalent) in pentane was cooled to -78°C for 10 minutes. Pentafluorophenyl lithium was slowly added via cannula, and the resulting solution was stirred at -78°C for an additional 3 hours, then allowed to gradually warm to room temperature overnight. The solution was filtered, leaving behind an orange-yellow precipitate, which was dried in vacuo.
228