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Electronic Theses and Dissertations
1979
Rhodium Complex Catalyzed Alcohol Carbonylation Reactions
Joseph Leo Nothnagel
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Recommended Citation Nothnagel, Joseph Leo, "Rhodium Complex Catalyzed Alcohol Carbonylation Reactions" (1979). Electronic Theses and Dissertations. 5041. https://openprairie.sdstate.edu/etd/5041
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ALCOHOL CARBONYLATION REACTIONS
BY
JOSEPH LEO NOTHNAGEL
A thesis submitted in partical ful fillment of the requir ements for the degree Ma ster of Science , Major in Chemistry , South Dakota State Univers ity
"SOUTH DAKOTA STATE UNIVERSITY LIBRARY RHODIUM COMPLEX CATALYZED
ALCOHOL CARBONYLATION REACTIONS
This dissertation is approved as a creditable and
indep endent investigation by a.candidate for the degree ,
Master of Science, and is acceptable as meeting the dis
sertation requirements for the degree, but without imply
ing that the conclusions reached by the candidate are
necessarily the conclusions of the major department .
Thesis adpiser Date
Head , Chemistry Department Date ACKNOWLEDGEMENTS
To Dr . Ols·on who, like all great teachers, gave far more
than he received;
To my wi fe who , as a loving wife, put up with one too
many accidents;
To my parents , who have always been with me, TABLE OF CONTENTS
page
. .. , .....•••• ," ...... ,, . .- •• 1 INTRODUCTION . ,, • • · · .· .· ,,•• · .-. · .,
...... , , ,. ••• •• HISTORICAL SECTION · • • • • ...· .. • 3 : _. .. : ,· .- .- ,: , , , •
.. ' ••••• ...... • EXPERIMENTAL SECTION . . I . ... · .. • � : ,· . • • 21
· · · ... .. · Preparat ion of Cuprous Bromide.-, , : ,: �. . . :. .. 26
· • · . • • • • Preparation of o--Bromochlorooenzene , : • 27
· Drying of Zinc Chlor ide ...... , ... . 29
Preparation of o-Chlorophenyl (d ichloro-.} - phosphine...... 3 0
Preparation of o�BromophenyL{dichloro}:�· ·
phosphine ...... "' . • • 3 1
Preparation of o-Chlorophenyl (dimethyl)�
phosphine . • . . . • . • . . • . . • • ...... • . . • • • • • • • . . 3 1
Preparation of o-Bromophenyl (dimethyl) - phosphine .••...... ••.•� • • • . • . • • • . • . • • . • • • • • 3 3 Preparation of Dimethylphenylphosphine. ... . 33
Preparation of Carbonyl(chloro)bis �-chlorophenyl (d imethyl) pho sphine] - rhodium (I) . • • • . • • . . . . . • • • . . • • • . • . . • . • • • • • . • 34 Preparation of Carbonyl (chloro) bis J9-bromophenyl(d imethyl) phosphine] - rhodium (I) ••.••••.•••.••.••" ...... •. • • • . • • . 35 Preparation of Carbonyl (chloro)bis� @ imethylphenylphosphine] - rhodium(I} . • • •• • " . 35 Preparation of Carbonyl(chloro1bis £>-chlorophenyl (dimethyl}.phosphine:J -. iridium(rJ...... 36
. • Kinetic Stud ies •..••••.. •. • , ••· ...... �···· 37 page
Carbonylation Kinetics...... 3 8
DISCUSSION AND RESULTS, • • , •.••••.• 40
Kinetics ...... " • •••" • , . •...... 41
Discussion of Results. for Oxid ative Addition Reaction ...... 43
Discussion of Infrared Spectra ...... 55
Iridium vs Rhodium Complex . • • • .. • • .. • • t • • • • • 59
Carbonylation Kinetics •••••.••• ...... 59
SUMMARY...... 63
APPENDIX...... ' ...... 65
BIBLIOGRAPHY. . . . - . . - . . - ...... - ...... - . . � . 82 LIST OF TABLE
page
TABLE' I
Spectroscopic Data for Listed complexes.·,, 42
TABLE TI
Data for Addition of Me! to MCL (CO) (X) 2 in To luene at 220 c...... 45
TABLE III
Data for Addition of MeI to MC l (CO) (X) 2 in Toluene at 220 C and at Concentration of MeI as Listed...... 46
TABLE IV
Acetolysis rate Ratio for Cis and Trans- 2-Halocyclohexylbrosylates • . •••••.• ••• •••• 4 9
TABLE V
Ultraviolet Spectra of the Phosphine
P • ••••••••• •••••••• •••••, • • • • • • • • • • Me 2 R • • • 51 TABLE-- VI
Ligand Preference Toward Class (a ) or Class (b) Metal Ions...... 54
TABLE VII I �co for the Complex Rh Cl (CO) [ Co-xc H }- · 6 4 ( CH ) • . • . . . • • • • . . • • • • . • " • •· • • • • •. • • • • " • 3 2 p J 2 • 56 TABLE VIII Data for the Carbonylation of MeOH in Acetophenone at 1650 C in the Presence of Methyl Iodide Promoter, RhCl 3·3 H20 , and the Indicated Phosphine Ligand Added" •· •· ..•, 61 LIST OF FIGURES
page , FIGURE' I
Kinetic Data for the Oxidative Addition· Reaction Methyl Iodide and the· Listed
· ° ...... Metal Complexes at 22 c ...... , ".,, � , 44
-- FIGURE'· TI Kinetic Data for the Carbonylation Reaction of Methanol in the Presence of Methyl Iodide Promoter and Pho sphine-
Metal System Listed at 165° c •••.••••••••• 62 RHODIUM COMPLEX CATALY ZED ALCOHOL
CARBONYLATION REACTIONS
Abstract
Joseph Leo Nothnagel
Under the Supervision of Dr . Edwin Olson
The oxidative addition reaction of methyl iodide to rhodium or iridium complexes were investigated, incorpor- ating various ortho-substituted dimethylphenylphosphine ligand s· on the metal comp lexes. Evidence of rate enhance- ment for the oxidative addition reaction of the various complexes with methyl iodide wa s found , due to the influ- ence of the ortho� substituents.
The complexes studied were:
Carbonyl (chloro)bis�(o-chlorophenyl (d imethyl) phoshine]-rhod ium (I)
Carbonyl (.chloro)bis-Co-bromophenyl (dimethyl ) pho sphineJ�rhodiurn(I)
Carbonyl (chloro)bis-(d imethylpheny lpho sph ineJ rhodium(I }
Carbonyl�hloro )bis-Co-chlorophenyl (dimethyl) phosphineJ-iridium (I)
The increase in relative reaction rates for the com- · plexes were found to proceed in the order.: Br> Cl ) H for the ortho-phenyl substituent and Ir (Il) Rh(�) for complexes of similiar ligand type . INTRODUCTION
Carbonylation of alcohols in the presence of vari ous
base metals has been investigated extensively . Reaction
over these catalysts is characterized by the use of high 1 temperatures and pres sures . In comparison to the wide
spread attention that the base metal catalysts have
received , the noble metal catalysts have received very
little attention . Mo st recently , investigation of noble metal catalysts have met with .spectacular succ ess . For
the carbonylation of methanol , Roth reported a new com- rnercial synthesis of acetic acid using a homogeneous
iodide-promoted rhodium catalyst wh ich has such extreme
reactiv1ty that it will convert methanol to acetic acid 5 in 99% selectivity at pressures as low as one atmo sphere.
None of the various by-products. characteristic of cobalt-
cataly�ed reactions were found when using rhodium.
The carbonylation is believed to proceed through a
series of steps beginning with rapid conversion of methano l
to methyl iodide . Methyl iodide then undergoes an oxidative 8 addition reaction with a d square-planar rhodium (! ) comp lex 6 to form a d six-coord inate alkyl rhodium (III) species .
Rapid insertion of carbon monoxide into the rhodium-alkyl 2
bond to produce an acylrhodium(I II) complex , followed by reaction of this complex with water to form acetic acid and the original rhodium(!) complex , completes the cylce.
The rate-determining step of the carbonylation reaction of methanol with carbon monoxide has been shown to be the oxidative addition of the alkyl halide with the catalyst. The purpose of this project was to investigate the possible rate enhancement , due to anchimeric assistance rendered by the ortho-substituted phenylphosphine ligand directly to the metal center, of the oxidative addition reaction of the alkyl halide with th� catalyst� The substituted groups were; Br , Cl , and H. Also desired was a study of difference in relative reaction rates of iridium complex and a rhodium complex with s1miliar ligand type groups. 3
HISTORICAL SECTION
For over forty years, the scientific and industrial communities have been interested in the reaction of 1 carbon monoxide with organic mol�cules. In the reaction, which is known as a carbonylation reaction, carbon monoxide adds to the organic mo lecule in the presence of a catalyst.
Carbonlylation reactions lead to a wide variety of products; such as, aldehydes , alcohols, ketones and carboxylic acids . 2 The "Oxo " reaction is the best known carbonylation reaction ._ catalys� . RCH=CH + CO + H RcH cH - H and or _ cH cH 0H 2 2 2 2 8 I � 2 2 Rearrangement of the carbon chain of the starting alkene during "t:he course of the "Oxo " reaction, leads to a variety of isomers of the aldehyde and alcohol as products.
Recently, the Monsanto Company has used a carbonylation reaction to produce acetic acid from methanol and carbon monoxid·e.
catal st CH - 0H 7000-t0000 psi) 3 � ° 8 2500 - 350 � = - 8 S.. 88 kJ/mol
= -13 7.8 6 kJ/mol
Under reaction conditions cited , but with no catalyst present, the equilibrium is shifted against the acetic acid. 4
An increase in reaction temperature will cause the equilibrium constant to decrease . For the carbonylation of methanol to occur, a catalyst must be used to give a reasonable yield of acetic acid as product. The Monsanto
Company utilize s a rhodium cataiyst in their carbonylation of methanol with carbon monoxid e.
Initially, the catalyst used in the carbonylation of methanol consisted of acidic compound s; such as, boron triflouride and phosphoric acid alone or in conj unction with metal salts . The se catalysts required drastic reac- tion conditions: carbon monoxide. pressure in the range of
10, 000 psi and reaction temperature greater than 3 00° c.
Side reactions under such severe conditions were great.
The major by-products were alkanes and longer chain alcohols.
In 194 1, Reppe and coworkers applied "Oxo" technology 2 to the carbonylation of alcohol � Metal carbonyls, especially those of iron, cobalt and nickel, were shown to be effective catalysts in the carbonylation of methanol.
Reaction conditions were milder than tho se with the acidic compounds: carbon monoxide pressure in the range of 3000 ° to 5 000 psi and reaction temperature in the range of 250 to 210° c. A halogen or halogen containing promoter had to be present for the catalyst to function effectively . 5
Results of carbonylation reactions showed the reactivity order of the metals to be Ni) co > Fe and that the order
of the effectiveness for the halogen promoter to be I > Br) Cl.
Utilizing a cobalt catalyst and an iodide-containing promoter , Badisc.he Aniline und Soda Fabrik reported molar
selectivity of the methanol and carbon monoxide to acetic 4 acid at approximately 90% for both reactants . Major by-product of carbon monoxide was carbon dioxide via the water gas shift reaction.
The hydrogen reacts with the methanol to produce methane and ace�aldehyde. Additional liquid by-products inc lude ethanol, propionic acid , propionaldehyde, butyraldehyde , and butanol with propionic acid making up about 5 0% of the 3 total by-products .
In 196 8, Paulik and Roth reported on a homogeneous liquid phase catalyst system of an iodide promoter and 5 rhodium catalyst. The sel�ctivity was extremely high {99%) and the reaction conditions were very mild , the mildest reaction conidtions yet reported for the carbonyla-
0 tion of methanol. The reaction temperature was 175 c and the carbon monoxide pressure could be as low as one 6
atmosphere . Kinetic studies conducted by mea suring the rate of carbon monoxide pr essure drop during the carbonyla tion reaction of -methanol produced experimental rate expressions which suggested reaction orders 1, 1, 0 and 0 with regard to CH 0H and co, respectively. Further Rh, I, 3 inve stigation of the catalytic system indicated that there was little differenc e in the catalytically active complex found in-situ when different forms of rhodium and iod ine were used . Rh 0 ·5H 0' RhCl ·3H 0' RhC l(CO) (PPh ) , 2 3 2 3 2 3 2 Rh(co1 c1 , HI , CH I and r all gave reaction rates 2 2 3 2 within a 10% range . Paulik and Roth reported that a slight reac tion rate enhancement could be realized going from a nonpolar solvent to a polar solvent . The methanol concen tration was varied by a factor of 3.3 and the rate of car bonylation was constant within 2 0% . The reaction rate wa s independent within 7 % of. carbon· .monoxide pressure down to one atmosphere . Paulik and Roth sugge sted a ·mechanism for the carbony lation ·of methanol, which explains the experimental obser vations of first order with respect to catalyst and promoter 6 and zero order with respect to reactants. 7
(Rh complex] + H 71 3 lir�h complex
k co 2 CH 3 J � �th complex · co] k 3 H 3 � Cy=O Rh' complex I I
k� H + (Rh complex] + CH COOH + 3 H20 ) 3 CT=O HI RhI complex Ii
Initially, hydrogen iodide reacts with methanol to
produce methyl iodide in an equi·librium reaction. In the
next step, methyl iodide coordinates to the Rh complex in
an oxidative addition reaction . (The term "oxidative
addition" has come to be used to designate a rather widely
s pread class of reactions , generally of low spin trans ition 8
* metal complexes, in which oxidation, i.e .. , an increase
in the oxidation number of the metal, .is accompanied by ** 8 an increase· in the coordination numbe:r. } Mechanistic-
ally, the oxidative addition step is the attack of metal
on alkyl carbon displacing the ha lide anion. Th� metal
complex is most likely, either Rh(COJ I or (Rh(co1 rJ • 3 2 2 Morris and Tinker found these two complexes in situ when 9 they studied the same system that Pualik and Roth studied.
The third step involves the coordination of the carbon monoxide and the subsequent insertion reaction of the
methyl group and the carbonyl • . Once the acyl complex i$
formed, it is hydrolyzed to yield acetic acid and regen-
eration of the rhodium complex.
*The des ignation "Low Sp in" refer s to those transition metal complexes in which the ligand field splittings are sufficiently large that the_ d electrons first fill up all the available bonding and nonbonding orbitals before beginning to populate the antibonding orbitals.
**Designation of oxidation numbers follows the generally accepted convention of "a ssigning" to the ligands in a complex the shared electron pairs which constitute the metal-ligand bonds. According to this convention the hydrogen ligand in hydride complexes is assigned the oxi H H dation number 1- . The Ir atom in Ir(CO) tPCC 6 5) 2 2 c1 the oxidation number 3+, etc . iJ 9
In 1976 , Jes Hjortkjaer and Vagn Wa lther Jensen reported on their investigation of the rhodium complex 10 catalyzed caroonylation of methanoi. Kinetic studies had been conducted and reaction orders, rate constants · and activation energies for the carbonylation were deter- mined .
r = k • (Rh} (I} k k = 0 exp C-E/RT). 6 k = 3 . 5 x 10 1/mol sec 0
E = 6 1,5 kJ/mol
The rate expression held for a· temperature span from 150 0 to 230° c, and at concentrations of methanol and carbon monoxide pressures above 0.5 mo l/l and two atmosphere respectively.
Hjortkjaer and Jensen assumed that the rate-deter- mining step of the carbonylation. reaction wa s the oxidative additiqn step . They proposed two different mechanisms which agreed with their experimental data for the carbony- lation of methano l. 10
(I) CH 0H + HI CH I + H 0 3 3 2 CH3I [Rh complexJ CH 3 ) [rh complex
+H 0 -HI 2 +c o j -CH3C�OH
CH3r- c;:o H3 comple ( lf complex [ II h Rh j [I . c (II) CH 30H + Hr CH3I + .H20 � (
complexJ complex • [Rh ) + +H -HI co (Rh +CH3I co) -cH3COOH
H31- co CH 3 complex l complex l r j f [�h , l c1 11
Since the experimental data indicated no shift in the rate-determining step over the range of temperature and concentrations at which the carbonylation reaction wa s run , Hjortkjaer and Jensen calculated rate expressions which did not take into account any shift in the rate determining step. They argued that a catalytic cycle with CH 0H + HI--7 CH r + as rate-determining would 3 3 H2o lead to a reaction rate independent of rhodium . A cataly tic cycle which designated the coordination of carbon monoxide as rate-determining would result in a rate expres sion with the concentration of carbon mono)cide as first order . The other two steps , the oxidative addition of methyl iodide or the insertion of the carbonyl, were the only steps which could be rat�-determining in a catalytic cycle. Hjortkjaer and Jensen determined the rate expres sions for each of the two mechanisms assuming either the oxidative addition or the insertion as the rate-determining step. Introducing simplifications to reduce the expressions led to the results that only the oxidative addition of methyl iodide was plausible as the rate-determininq step in the carbonylation of methanol . Although, the rate-deter mining step wa s shown to be the oxidative addition step, no information was available to distinquish which of the two mechanisms was correct . 12
Spectroscopic studies of the nature of reactive intermediates involved in the catalytic cycle of the carbonylation of alcohols with a metal catalyst and a halide (HI) promoter wa s performed by Forster of Monsanto
Company . Forster concluded that the alkyl halide adds first to the metal complex and then the carbon monoxide 6 coordinates to the metal complex .
CH30H + HI + (Rh complex] + -s- 1-0-w�> �H3h complex . � Jj .
H ) -H 3 co 3 , �h complex + Rh complex • � lj . � I c H � 3 ) f C=O RhI complex t I
H CH [Rh complex] 3 3-gOH + + T ) C=O RhI complex HI I I 1 3
Extensive studies have been made on the oxidative 8 addition of d complexes in the last several years. Mo st 8 notable of the d complexes are the square-planar iridium(!)
complexes of the typer Ir{CO) L Y (Y =Cl, Brr I, etc.; 2 11 12 13 8 L = P(C H } , P(C H ) CH etc .) � , , d 6 5 3 6 5 2 3 , Complexe s oxidatively add organic halides (RX = CH r, c a cH Br, 3 6 5 2 etc.} . A mechanism has been proposed for the oxidative 8 addition of the organic halide to the a complex.
L $+ �- co [L2Y(CO) Ir-�R--X] l Ir l RX y ___ L
R co L I Ir . (X) YI LI (Y)--1- X
The oxidative addition is believed to be SN2 type attack with inversion of configuration at the carbon, with at least partial halide displacement, through a highly unsym- metrical transition state . 8 Co nsidering various kinetic behavior s (activation parameters, solv ent e ffects, substi- tuent effects for the substituted benzyl halide s, etc.) , the above mechanism is reminiscent of the Menschulkin reac
. 14 15 tion, another SN2 type reaction . '
SOUTH DAKOTA STATE UNIVERSITY LIBRARY 349l�O 14
. . . 8 Reac tiv ities o f d complexes reflect their tendenc ies 6 11 to undergo reaction to d complexes. Tendency to go to 6 a d complex decreases from left to right and from bottom 12 to top of the periodic table . Assuming constant ligand environment , reactivity toward oxidative addition decreases ° 0 0 r I I I I II I I 8 os > Ru > Fe , Ir ) Rh > Co > Pt ) Pd I=)} Ni ' AU . 8 For a given d metal atom , the reactivity is expected to be enhanced by ligands which favors higher oxidation states and by ligands which favor s the formation of four-coordin- 8 41 42 ate d complexe s. , The observed reactivity rates for various complexes agree fairly well with predictions . I Ir [P (.c H ) ca J (CO} Cl 6 5 2 3 2 I H ) ] (C O) Cl, Rh (P (C6 5 3 2 I lG, Rh H ) ] (CO) Cl (P (C6 5 3 2 The basic ity of the tertiary phosphine bound to the metal or ligand steric effects due to the bulkiness of the phosphorus substituents are important factors in an oxida- tive addition reaction. In 1971 , Va ska and Chen reported 19 on studies which investigated these factors. They re ported that the ability to predict relative reaction rates for a given set of complexes can be most difficult if ster ic factors of the R substituents are not nearly similiar . The I complex studied was trans- (Ir Cl (CO) (R3P) 2J where the R3P substituents are tertiary phosphines. Vaska and Chen 15
observed that when complexes in wh ich the ligands are
* isostructural or nearly so, the log (orAH ) is k2 2 inversely proportional to the Hammet ' con stant for the
para-substituent in the aryl phosphine ligand Cp-xc H ) P, 6 5 3
The log k2 is directly proportional to the basic ity of the
tertiary pho sphine .
14 .1 (X}
= Cl, H , CH , CH 0 } ex 3 3
IrCl (CO}L o ( > o IrCl (CO) L 2 + 2 2 2 :2-1
An example to demonstrate a distinction between the electronic and steric factors inf luencing reactivity was cited by Vaska and Chen: when the ligand L for the com- plex prcl (CO} L ] is cc F ) P or (o-CH c H ) P� no reac 2 6 5 3 _ 3 6 4 3 tion with oxygen is observed, The inactivity · of the former can be attributed largely to the lack of requ ired electron density on the metal, but the inertness of the latter mu st be solely due to the steric effect (ortho-CH ) which over 3 rides the favorable electronic disposition of basicity of the ligand .
In 1972 , Ugo and Cenini commented on the electronic and steric effects of various iridium (!) complexes. They observed in their kinetic studies tha t drastic changes can be obtained in reactivity rates by introducing a phosphine 16
ligand into the coordinate sphere of the metal or by small
changes of the steric and/or electronic properties of the 2 0 substituents bound to the pho sphorus atom� The tendency
for a metal complex to undergo oxidative addition is en-
hanced by decreasing the bulk of. the lig.and L and by in- 2 1 creas ing the donor power of the ligand L. �go and
Cenini proposed a three-center mechanism for the oxidative
addition of methyl iodide to an iridiwn complex, A three-.
center mechanism is similiar to the simple SN2 mechanism
(Menschulkin-type reaction} upon which Halpern patterned
his proposed mechanism for the· oxidative addition of a
variety of organic halides to iridium(I1 complexes of the
type Ir (CO} L Y (Y = Cl r Br, I � L = P (c .H l 3 r P (C H ) - 2 6 5 6 5 2
CH , P tc H 1(C ) • The difference between Halpern's 3 6 5 H3)2 8 mechanism and the three-center mechanism of Ugo and Cenini
centers on whether inversion at the carbon atom is required
or not . In the three-center mechanism, a nonconcerted, · rather polar three-center SN2 attack occurs in which in�
version or retention may both occur depending on the amount
of Ir-ha logen bond making in . the transition state . Ugo and Cenini found a highly negative f value for the oxidative addition of methyl iodide to the complex IrCl (CO} [P(p-Z-
c H ) J , z CH 0, CH , H, F, Cl, A highly negative 6 4 3 2 = 3 3 f value implies that a large positive charge is formed into
the iridium atom in the transition state. 17
In 1969, Deeming and Shaw reported on studies con ducted to investigate electronic effects of oxidative addition of methyl iodide to RhCl (CO} [P (p-zc H ) 6 5 � 2
(Z = F , H , OMe} . With a para-substituted series of phenyl- phosphines, the ster ic effects are held constant and the relative reactivity rate changes should be due almost en- tirely to electronic effects. Thu s, for the oxidative add- ition of methyl iodide to the above para-substituted com- plexes, relative rate constants for z = F, H, OMe are 1.2, 5.5, and 44 . 3 respectively. Results agree with predictions ba sed on increas·ing donor power of the ligand through the phosphorus atom to the rhodium, the rate increases in the 22 order F < H < OMe._ Drastic changes in relat�ve reactivity rates can be realized through electronic effects, bu t the steric effects can override the electronic effects if the ligand is bulky enough to block or hinder the SN2 type reaction. With bulky ligands such as PBu Et or PBu Ph� steric effects are 2 2 23 4 dominant and result in very inert complexes, ' 2 Most kinetic studies of .the oxidative addition of an alkyl hal ide to rhodium or iridium complex have centered their attention on electronic effects of the tertiary phos- phine operating via the phosphoru s ligand atom. In 1974 , Miller and Shaw reported on a ligand system which interacted 18
directly with the iridium atom , rather than interacting 21 via the phosphorus atom . This type of interaction
wh ich is intramolecular and operates through space is
called neighboring group participation or anchimeric assis
tance. The ligand investigated was ortho�ethoxyphenyl- (dimethyl ).pho sphine . Such donation and activation is
shown schematically.
;
Cl ______� _.,... p " I Ir J --. I - p ------��------G•D I I I 0 I &--- Me The above diagram shows how electron donation from the
o-methoxy oxygen would increase the nucleophilicity of the
irid ium by stabilizing the po sitive charge developing in the transition state, and hence lower the activation energy . 2 1 of the oxidative addition reaction .
An x-ray structural study of RhC 1 [AsMe (o-Meoc H ) J , 3 2 6 4 2 shows that the oxygen of the ortho-methoxy-group is co- 2 7 ordinated to the rhod iurn . This does not imply that there exists any co-ordination before the transition state in the 19
oxidative addition of methyl iodide to iridium complexes depicted in the above diagram. But it wa s argued by
Miller and Shaw that the X-ray structural study cited
gives reason to believe that there exists some interaction
of the ortho-methoxy-group and the iridium atom . If
there is some interaction , then that interaction would
become stronger during the formation of the highly polar
intermediate , believed to be involved in many oxidative . 33 a dd•i t•ion reactions. The kinetic studies Miller and
Shaw conducted compared trans-IrCl (CO} [PMe o-Meoc H ) 2 ( 6 4 ) 2 to trans-( rCl (C O) (PMe Ph) J and IrCl (CO) [PMe (p-MeOC H )) • I 2 2 2 6 4 2
Oxidative addition of methyl iodide to the above mentioned complexes were carried out in toluene solutions . The
disappearance of the iridium(!) complex was fol lowed spec-
trophotometrically by observing the absorption maximum at
ca. 430 nm . At greater than a 10-fold excess of methyl iodide, pseudo first order plots of log(A - A_) vs tirne(t) t
were linear to more than 8 0% conversion (A = absorbance) . The PMe (o-Meoc H ) complex reacted about 100 times faster 2 6 4 than the PMe Ph complex at 25.-3° C and about 8 0 times faster 2 21 than the PMe Cp-Meoc H } complex . 2 6 4 Both the p-MeO and the o-MeO substituted phenyl groups
increase the electron density on the iridium via the phos-
phorus atom , as compared to the unsubstituted phenyl group. 20
Sterically, the o-MeO substituted phenyl group should have retarded the oxidative add ition reaction over that of the p-MeO substituted phenyl group , The o-MeO group tend s to block the approach of the methyl iod ide to the metal atom . The kinetic data does not show this decrease in reaction rate; rather , the o�MeO substituted phenyl complex reacted approximately 80 times faster than the p-MeO sub stituted phenyl complex . Mil ler and Shaw believe that it is neighboring group participation by the o-methoxy group which overrides any steric constraints and accentuates
on the rate to vield� a 8 0 fold increase in relative reacti rate of the PMe (o-Meoc H } complex over the PMe Cp�Meoc H } 2 6 4 2 6 4 complex in the oxidative addition reaction of methyl iodide and these complexes. 2 1
EXPERIMENTAL SECTION
INFRARED.SPECTRA
The spectra of all compounds were obtained from -1 potassium bromide wafers in the.region 4000 to 400 cm , using 2.0 mg of sample in 0.10 g of potassium bromide or from neat on sodium chloride plates in the region
4000 to 650 cm-1• The spectra were obtained on a model
52 1 Perkin-Elmer grating spectrophotometer. Settings were: split program, in-1000; gain, 5; attenuator speed,
1000; suppression, 2; source current, 0.8 amps; scan time, 10 minutes. Preliminary infrared spectra were done on a Perkin-Elmer Infrared Spectrophotometer 700, using neat on sodium chloride plates or potassium bromide -1 wafers in the region 4000 to 650 cm .
NUCLEAR MAGNETIC RESONANCE SPECTRA
The nuclear magnetic resonance (NMR} spectra were obtained on a Perkin-Elmer Rl2B NMR spectrophotometer, operating at room temperature.
MASS SPECTRA
The mass spectra were ootained on a Finnigan Model
3000 Gas Chromatograph Peak Identifier, an integer resol ution Gas Chromotograph;Mass Spectrometer system, A solid probe was used to introduce the sample into the instrument 22
The range of the Ma ss Spectrometer system wa s O to
500 amu .
ELECTRONIC SPECTRA
The electronic spectra were obtained in solution
on either a Beckman DK-2A ratio recording spectrophoto
meter or a Beckman DB spectrophotometer using one centi
meter silica cells. Kinetic studies were done using a
Turner Spectrophotometer Model 330.
ETHYL ·ETHER · (ANHYDROUS)
The ethyl ether (anhydrous) was obtained from Ma l
linckrodt , Inc . and used as received .
THIONYL CHLORIDE The thionyl chloride wa s obtained from Fisher Scienti-
fic Company and distilled fresh at a constant boiling
point of 76° c under nitrogen.
CUPRIC SULFATE-5 HYDRATE
The cupric sulfate-5 hydrate was obtained from J.T.
Baker Chemical Company and used as received .
SODIUM BROMIDE
The sodium bromide wa s obtained from Matheson Coleman and Bell and used as received .
MAGNESIUM TURNINGS
The magnes ium turnings were ootained from Fisher
Scientific Company and used as rece ived . 23
IODOMETHANE
The iodomethane wa s obtained from Aldrich Chemical
and dried over sodium metal,
' o-DIBROMOBENZ"ENE
The o-d ioromooenzene was ob'tained from Aldrich Chemical
and used as received .
IRIDIUM rII CHLDRTDE
The iridium III chloride wa s obtained from Alfa Products
and used as received .
"RHODIUM III CHLORTI>E
The rhodium III chloride wa s· obtained from Alfa Products
and used as received .
SODIUM SULFATE (ANHYDROUS} The sodium sulfate (anhydrous} wa s obtained from Drake
Brothers and used as received .
COPPER TURNINGS
The copper turnings were obtained from Fisher Scienti
fic Company and used as received.
POTASSIUM BROMIDE The potassium bromide was obtained from Matheson Cole�
. man and Bell and dried in a vacuum oven at 700 C for 24
hours and then stored in a desiccator until used. 24
PHOSPHORUS 'P.ENTOXIDE
The pho sphorus pentoxide wa s obtained from J.T .
Baker Chemical Company and used as received .
ETHYL ACETAT·E
The ethyl acetate wa s obtained from Eastman Kodak
Company and wa s distilled under nitrogen and degassed with nitrogen prior to use
CYCLOHEXANE
The cyc lohexane wa s obta ined from Eastman Kodak
Company and wa s distilled under nitrogen and degassed with nitrogen prior to use .
METHANOL
The methanol wa s obtained from Fisher Scient ific
Company and wa s distilled under nitrogen and degassed with nitrogen prior to use .
ETHANOL
The ethanol was obtained from Fisher Scientific
Company and wa s distil led under nitrogen and degassed with nitrogen prior to use .
SODIUM
The sodium metal wa s obtained from Fisher Scientific
Company and used as received. 25
TETRAHYDROFURAN
The tetrahydrofuran was obtained from Eastman Kodak
Company and was dried by adding sodium metal and benzo phenone under nitrogen. After reaction had taken place ,
the resulting deep blue colored solution was distilled ° under nitrogen at a constant 65 c, using a three foot column packed with glass beads. The tetrahydrofuran
was stored under nitrogen until it was used •.
PHOSPHORUS TRICHLORII>E
The phosphorus trichloride was obtained from J.T.
Baker Chemical Company and used as received .
CALCIUM CHLORIDE (ANHYDROUS)
The calcium chloride (anhydrous) wa s ·obtained from
Mallinckrodt, Inc. and used as received .
NITROGEN
The nitrogen was obtained from Linde Specialty Gas
Company and was pas sed through a four foot column con taining calcium chloride-phosphorus pentoxide mixture to remove traces of moisture .
CARBON MONOXIDE
The carbon monoxide was obtained from Linde Specialty
Gas Company as wa s passed through two columns prior to use. The first column contained activated charcoal to remove traces of iron complexes, The second column 26
contained calcium chloride-phosphorus pentoxide mixture to remove traces of moisture .
ACTIVATED CHARCOAL
The activated charcoal was obtained from Fisher
Scientific Company and was used as rece.ived. o-CHLOROANILINE
The o-chloroaniline was obtained from Matheson Cole- man and Bell and was distilled under nitrogen at a con ° stant ooiling point of 206 c. The o�chloroaniline wa s stored und er nitrogen until it was used .
DICHLOROPHENYLPHOSPHINE
The dichlorophenylphosph ine wa s ootained from Fisher
Scientific Company and wa s distilled under nitrogen at a
. 0 constant boiling point of 217 C and then was stored under nitrogen until it was used,
PRE.PARATION 'OF CUPROUS BROMTDE The cuprous bromide wa s prepared as outl ined by 3o Vogel� Copper sulphate crystals (100 .0 grams) and sodium bromide (58.3 grams} were dissolved in 500 ml of warm water . While stirring the solution� powdered sodium suphite (25.3 grams) wa s added over a fifteen minute period . After the blue color had been discharged from the solution, the solution wa s stirred for an additional thirty minutes· . The white solid was collected in a 27
Buchner funnel and wa shed three times with water. The cuprous bromide was used immediately .
'·' 'PREPARATION OF o..:BROMOCHLOROBENZENE·
The o-oromochlorobenzene wa s prepared using the 29 Sandmeyer react ion. A mixture of o-chloroaniline
(64.2 grams} and 1 75 ml of constant boiling point hydro bromic acid lsp gr, 1,48; 100 ml contains 7 1 grams of
HBrl was prepar ed in a 1 liter flask . The liter flask
0 was set in an ice bath. The solution was cooled to o to --5 0 c. The solution was continuously stirred using a magnetic stirring bar and stirring motor. Sodium nitrite solution (3 5,0 grams in 70 ml of wa ter) wa s added over a period of 40 minutes, while maintaining the
0 ° o-chloroaniline solution between o and -5 c. An excess of sod ium nitrite solution wa s added until the o-chloro- aniline solution tested positive for nitrous acid (starch- 3 2 po t ass.ium. io. d.di e paper test 'L •
A solution made by mixing freshly prepared cuprou s bromide (approximately SO grams) and 48 precent hydro brornic acid (40 rnlJ was added to the 2000 milliliter flask of the steam generator depicted on following page .
Stearn was admitted from the steam generator and a hot plate wa s used to heat the so lution to boiling . The o-chlorophenyldiazonium bromide solution prepared above, 28
A steam distillation apparatus was constructed as diagramed below.
Separatory Funnel
,-·. . _..-' __ ' / 11, ."' , / ' ; i·Iij, . . 'I . ,.,.L.,,.-.1' '
5000 ml Boi.:.ing Fl.ask
2000 ml Boiling Flask
250 ml side arm Boiling Flask 29
was added to the boiling solution via the separatory
funnel , over a 50 minute period . After all of the o
chlorophenyldiazoniwn bromide solution had been added to
the cuprous bromide solutionr steam distillation was . cont inued until no more organic material distilled
(6 hours} • The aqueou s layer wa s separated from the
organic layer and was discarded . The organic layer
was dried over anhydrous magnesium sulphate (24 hours) •
The crude o�bromochlorobenzene was distilled under ° ° .nitrogen and collected at 199 to 201 c boiling point
range (a colorless liquid ) . The infrared and NMR spectra
conformed with that of literature spectra for · o-bromo-
chlorobenzene .
DRYING OF ZINC CHLOR'R}E
The zinc chloride was obtained from Mallinckrodt,
Inc. and dried by the method outlined in Inorganic 28 Synthesis. Finely ground zinc chloride (31. 0 grams)
was placed in a three-neck flask and freshly distilled
thionyl chloride (200 ml) wa s added under nitrogen .
The mixture wa s allowed to stand for twe lve hours. The
thiony l chloride was distilled off and any excess thionyl
chloride was removed in vacuo using a dry nitrogen bleed .
After the vacuunf the zinc chloride was placed under a ° vacuum for four hours at 40 C to finish the drying process. 30
PREPARATION OF o-CHLOROPHENYL (dichloro)PHOSPHINE
The o-chlorophenyl(dichloro) phosphine was prepared 31 by the method of McEwen,. Fountaine, Schul tz and Shiau.
A Grignard reagent was prepared in a 500 milliliter
three-neck flask under nitrogen from magnesimn turnings
(4.8 grams, 0. 2 g-atom) in dry tetrahydrofuran (50 ml )
and a solution of o--bromochlorobenzene (38. 2 grams,
0.2 mol in 150 ml of tetrahydrofuran} .
The solution of dried zinc chlor ide (27 .2 grams)
.and dry tetrahydrofuran (200 mll wa s added over a period
of 40 minutes, to the Grignarq reagent prepared above .
The Grignard solution was maintained at a temperature of ° -5 to o0 c and wa s continuously stirred with a magnetic stirring bar and stirring motor .
A solution of phosphorus trichloride (50 ml, 0.57 mol } in dry tetrahydrofuran (150 ml } was prepared in a
1000 mill iliter three-neck flask , and the contents were ° kept in the vicinity of -20 c. The organo-zinc halide
reagent was added over a period of 50 minutes to the cold
phosphorus trichloride solution under nitrogen with stir-_
ring . The resulting solution was allowed to warm up to
room temperature . The mixture was refluxed for four hours with a slow continuous stream of nitrogen flowing through
the reflux apparatus. The solution wa s allowed to cool 31
down to room tempe rature and was filtered under ni trogen .
The light yellow filt rate was distilled to remove the
solvent and the resultant liquid was frac tionated under
reduced pressure . The product wa s obtained as a color- . 0 less liquid 3 8.2 %, 16 ,3 grams (B . P . � 74 cat 0.45 mm
torr} . Consult Appendix for the in frared and NMR spectra
of the compound .
PREPARATION OF O··BROMOPHENYL C_d ic hl·or·o·) PHOSPH'INE
The o-bromophenyl (d ich loro) phosphine was prepared 3 1 . by the method of Mc �wen , Fountaine , Schult z and Shiau .
A siroiliar procedure as de scribed above for the prepara-
tion of o-chloropheny lldichloro) phosphine was �sed in the
preparation of o-brornophenyl (dichloro} phosphine. o-Di -
brornobenzene (47.l grams , O�� mol} was used in place of ·
o-brornochloroben zene � The product was obtained as a
0 0 coloroless liquid 3 1.3 % , 16 ,1 grams (B .P, , 54 to 55 C
at 1,10 nun torr) . Consult Appendix for the infrared and
NMR spectra of the compound .
PREPARATION OF o-CHLOROPHENYL' (dimethyl'} PHOSPH��E
The o-chlorophenyl (d imethyl} phosphine was prepared 31 by the method of Mc Ewen, Fountiane � Schultz and Shiau .
A Grignard reagent in a three �neck 500 milliliter flask
was prepared under nitrogen from magnesimn turning s
(9.6 grams , 0 .4 g-atom l in anhydrous diethyl ether 32
(150 ml } and a solution of methyl iod ide (56.8 grams ,
0.4 moll in anhydrous diethyl ether ( 1 50 ml). A solu
tion of o-chloropheny l(dichloro) phosphine (16 ,.l grams ,
0.0 75 mol) in anhydrou s diethyl ether (50 ml) was added ' to the Grignard reagent with stirring over a period of
45 minutes� The Grignard reagent wa s maintained under
nitrogen at a temperatur of -15 0 to -1 0 0 c. The
reaction mixture was allowed to warm up to room tempera-
ture and then was ref luxed under nitrogen for two hours •
. The mixture was then hydrolyzed at o0 c with a saturated
solution of annnonium chloride ( 1 50 ml} over a period of
two and one-half hours. Add itional water was · added to
dissolve any res idual white solid which had formed .
The ether layer was separate� from the aqueous solution .
The aqueous solution wa s washed with three separate
portions of diethyl ether (50 ml ) and the resulting
ether layers were isolated and added to the original
ether layer . The ether solution wa s dried over anhydrou s
magnesium su lfate (24 hours) • After the solution was
dry , the solvent was distilled off under nitrogen . The
resultant faint�colored liqu id wa s fractionated under · 4 7 ° reduced pressure, % , 7 • 6 grams (B . P. 4 6 C at 0.3 5 mm
torr) . consult Append ix for the infrared and NMR
spectra of the compound . 3 3
PREPARATION o-BROM OF OPHENYL (dim.e thyl ) PHOSPRINE .. c . .
The o-bromophenyl (dimethyl }phosphine was prepared 3 1 by the method of McEwen , Fountaine,- Schultz and Shiau .
A similiar procedure as described anove for the prepara tion of o-chloropheriyl (dime thyll phosphine was used in the preparation of o-bromophenyl(d �ethyl )pho sphine . o-Bromophenyl(dichloro) phosphine (15 .9 grams , 0.062 mol) wa s used in place of o-chlorophenyl (dichloro} phosphine .
The product wa s obtained as a colorless liquid , 43 .6%, ° · s.8 grams (B .P. , 54 c at 0.95 nun torr) . Consult Appendix · for the infrared and NMR spectra o f the compound .
PREPARATION OF DIMETHYLPHENYLPHOSPHINE
The dimethylphenylphosphine wa s prepared by the method 3 1 of McEwen, Fountaine , Schultz and Shiau . A similiar procedure as described above for the preparation of o chlorophenyl (d imethyl) phosphine .was used in the prepara tion of dimethylphenylpho sphine . Dichlorophenylphosphine
(15.1 grams , 0.085 mo l) wa s used in place of o-chloro phenyl (di chloro) phosph ine . The .product wa s· obtained as
9.3 0 a colorless liquid , 61.7% , grams (B .P. 6 2 C at 0.75
NMR mm torr ) • consult Append ix for the infrared and spectra of the compound . 34
PREPARATION OF CARBONYIJ ( chloro) (o·�nl:o:r·ophen J:-- ·B rs-: . y ·I (d imethyl) phosphineJ-rhodium:{1: )
The carbonyl (chloro l bis-[.o-chlorophenyl (.dimethyl 1 - phosphineJ �rhodimn(I ). wa s prepared oy the method of 21 Miller and Shaw . Ethanol (25 ml} was refluxed under
a stream of nitrogen for two hours. Rhodimn (III) chloride
(0. 50 grams, 2.4 mg-atom) was added to the ethano l and
refluxing continued with a stream of carbon monoxide
replacing the nitrogen for an additional sixteen hours .
· o-chlorophenyl (d imethyl l phosphine Cl. 5 grams , 7.0 rnmol)
was added to the resultant yel low solution at a ca . 60° c
in an atmo sphere of nitrogen and refluxing was continued
for three minutes. A solution of sod ium methoxide in methanol (4 ml , 0.87 M) was added to the resultant yellow
solution . The orange solution formed was ref luxed for
a further five minutes and then .cooled to o0 c. The
black precipitate that formed initially, was suction
filtered off and the filtrate wa s concentrated by rotatory
evaporation. The resultant solution was again cooled to
o0 c and allowed to stand for one week. The product formed as yel low crystals (0 .38 grams, 0.75 nunol) . Con
sult Append ix for infrared and mass spectra of the com-
pound . 3 5
PREPARATION OF CARBONYL (chloro } ·BIS-fi:>:-btotnop�eny-1 (di -.
methy 1) pho sph inel -RHOD rme CI )
The carbonyl (chloro )bis- [o-bromophenyl (dimethyl l
phosphineJ -rhodium (I} was prepared by the method of 2 1 Miller and Shaw. A similiar· procedure as described
above for the preparation of carbonyl (chloro )bis-(o
chlorophenyl (d imethyl } phosphineJ -r nodium{I } was used
in the prepar ation of carbonyl (c hloro 1 bis·- (o -.bromophenyl
(.dimethyl)_ phosphineJ -rhodium (!} . o-Bromophenyl (d imethyl) -
phosphine (1.5 grams , 7.0 rmnol } was used in place of . o-chlorophenyl C.dimethyl ) phosp�ine . After the resultant
solut ion was allowed to stand for one week , no crystals
The had appeared . solution was reduced in volume to
two milliliters by rotatory �vaporation. Ethyl acetate
(5 ml } and cyc lohexane (2 . 5 ml ) were added to the resul
tant solution and the solution was again cooled to o 0 c
for another week . The product formed a yellow crystals
(0 . 3 5 grams , 0.63 mmol} . Consult Appendix for the infra-
red and mass- spectra of the compound .
PREPARATION OF CARBONYL' (chloro ) BTS -[dimethylph enylphosphine] -
RHODIUM (Il
The c arbonyl (chloro } bis - (dimethy lphenylphosphineJ - 2 1 rhodium CI). was prepared by th e :method of Miller and Sh aw. 36
A similiar procedure as described above for the prepara
tion of carbonyl (chloro} bis-(o-chlorophenyl (dimethyl )
phosphinej-rhodium (I) wa s used in the preparation of
carbonyl (chloral ois ·�[d imet.hylphenylpho sphine1 -rhod . ium (I) • Di methylphenylphosphine Cl . grams, 7.2 mrnol) wa s used in place of o-chloroph nyl (dimethyl ) phosphine. After the
resultant solution wa s allow d to stand for one week , the
product formed a ye l low rysta. s (_0 ,73 grams, 1.54 mmo l) .
Consult Appendix for the 'nfrared and mass spectra of
'the compound •
· e - PREPARATION OF CARB_2B}'L(_q.9}-o ro) ars·�-{o·-ch'lorapheny i· (dim thy1)
pho sphine] -IRID IU'Mi:�l
The carbony lC-hloro ) bi s- [o-chlorophenyl (dimethyl)
phosphineJ -ir iditllll(I) wa s prepared by the method of Miller 21 -� bed for the and Shaw . A sim.ilia rocedure as descri preparation of carbonyl(chloro) bis-Co-chlorophenyl (di
methyl).phosphineJ -rhod ium (IJ wa s used in the preparation
of carbonyl (chloro ) bis (o chlorophenyl (dimethyl} phosphineJ
iridium (Il . Iridium (III} chloride (0.72 grams, 2.4 mg
atorn of irid ium) wa s used in place of rhodiurn (II I} chlor ide .
After the resultant solution wa s allowed to stand for one week , no crystals had appeared . The solution wa s re
duced in volume to two milliliters by rotatory evaporation . } Ethyl acetate [5 ml) and cyclohexane (2.5 ml were added 37
to the resultant solution and the solution wa s again cooled to o° C for another week . The product formed
as yellow crystals (0 .32 grams , 0.49 nuno l) . Consult
Appendix for the infrared and ma ss spectra of the compound .
KINETIC STUDIES
The ?- absorption the visible spectrum , for max in the four listed complexes was determined from their respective spectra.
A standard solu ion of methyl iodide in dry toluene
(2 . 8398 grams, 0.02 mol methyl iodide made to volume in a 100 ml volumetric flask, 0.2 M) wa s prepared and stored und er nitrogen until it wa s used .
Volumetric solutions of the four above mentioned complexes were prepared in dry toluene and stored under nitrogen until they were used .
The observ ing of the reduction in the maximum absorp- tion for each of the four complexes wa s done using a
Turner Model 330 spectrophotometer . A two milliliter portion of a giv·en complex had' been placed in a sample ho lder using a volmnetric pipette and a . two milliliter portion of methyl iodide wa s added in similiar fashion ,
The time wa s recorded with the addition of the methyl iodide solution and the max imum aosorption peak was 38
. obs erved to be reduced over time , A similiar procedure was used for each of the other three complexes. A plot
of log (A - A�} vs time (t) wa s made for each complex . t and an ooserved reaction rate wa s calculated for each ° complex . The above procedure was carried out at 22 c
for each of the four complexes listed .
CARBONYLATION KINE;TICS
The carbonylation of methanol wa s carried out in a method similiar to that used by Matsumo to and Ozaki
· in their studies of the effects of solvent on the car- bonylation of methanol catalyzed :Oy rhodium (I) complexes 7 in the presence of methyl iod ide promoter . A high pressure hydrogenation oomb equipped with a low pressure gauge was charged with 3.56 grams (4 ml) -methanol, 4.6 grams (2 ml} methyl iodide , 20 milliliters of acetophenone and 0.13 60 grams Rhc l ·3H o. The system wa s flushed with 3 2 ° nitrogen and then sealed . The bomb wa s heated to 165 c over a period of six hours . Carbon monoxide wa s added to 2 a pressure of 6,81 Kg/cm • The resulting pressure drop over time was observed . Reaction wa s continued until a constant pressure wa s reached . A plot of mmo l of carbon monoxide taken up vs time was constructed for each run . " -4· . 2xl0 ·mol} Rhcl • 3H o which consisted of .1360 grams (5 3 2 O . . � 4 and the indicated phosphine [5 . 2xl0 mol· J • 39
Run 1 no phosphine added
Run 2 0,0720 grams dimethylphenyl
phosphine
Run 3 0�0894 grams o-chlorophenyl
(dimethyl) phosphine
Run 4 0.1134 grams o�bromophenyl
(dimethyl) phosphine
Relative reaction rates were calculated from the data obtained from the four listed runs. 40
RESULTS AND DISCUSSION
Since the oxidative addition reaction has been shown to be the rate det rmining step for the· carbonylation
reacti '' o n of me thano an . c r an _ 1 a 'I'o: mono•xi �d e 31 any rate enhancement achieved in the oxidative addition reaction should increase the reaction rate of the overall carbony la tion reaction, Ev en though the Monsanto process to convert methanol o acetic acid operates at 99% selectiv- ity , reaction conditions are too severe to utilize high- er carbon alcohols without ex ensive rearrangement , when subjected to similiar carbonylation reactions as for methano l. By lowering the eaction temperature, rearrange- ment of the alcohol could be reduced , and higher yields of specific carooxylic acids 'could be achieved . With the aid of the substituted phenylphosphine on the metal com- plex , the activation energy of the oxidative addition reaction can be lowered . The lower the activation energy , the lower can be the reaction temperature for the overall carbonylation reaction , assuming the complex is stable enough to exist under the carbonylation react ion condi tions . In order to further study these effects, the kinetics of the reactions of the fol lowing ortho-substi- · · tuted phenylphosphine complexes were studied with alkyl halide . 41
KINETICS
The disappearance of the absorption maximum for the
four listed complexes in a solution of toluene at the
indicated temperature , wa s followed with time upon addi
tion of methyl iodid • Comp lexes studied and the maximum
absorption used for each complex are listed in Table I. w A direct corr elation xists bet een the disappearance
of the absorption maximum peak and the decrease in concen-
tration of the comple·x being studied . The oxidative addi- · 6 . tion of methyl iodide to the complex produces a d transi 8 tion metal comple � from a d t�ansition meta l complex . 6 . The d metal complex appears to absorb at a shorter wave
length than does th . a8 metal complex .. Miller and Shaw
used a simil iar procedur e as _described to study a series
of iridium (!) complexes in an oxidative addition reaction 2 1 with methyl iodide . They found that there wa s minimum 8 overlap of the .iridium (!) complex (d transition metal 6 complex) with that of the iridium (III} complex Cd transi-
tion metal complex) spectra . In like manner , there
appears to be only a minor overlap for the rhodium {!)
comp lex with that of the rhodium (III} complex spectrum .
No correction in measurement of the disappearance of the
maximum absorption peaks for the rhodium (I} or the
iridium(!) complexes were made , nor were there corrections 4 2
TABLE I
SPECTROSCOPIC DATA FOR LISTED COMPLEXES
COMPLEX , �AVELENGTH "-MAX, ABSORPTION ' USED ·-. ---ABSORBED carbonyl(chloro) ois 422 .5 nm
[dimethylphenylphosphjne] -� 333.0 mn 333 .0 nm rhodium(I l
Carbonyl(chloro lois� 356.0 nm 356.0 run
[o-chlorophenyl (dimethyl l phosphine] -rhodium ( .} Carbonyl (chlorol bi s� J58 ,0 nm 358 .0 IU!l
fiJ-bromophenyl (dlinethyll
phosphineJ -rhodium(I }
Carbonyl (chloro)bis� - 4 10.5 nm 410.S nm (o -chlorophenyl (dimethyl) ..... *
phosphine] -iridium(I1
*Below 3 7 0.0 run, absorption wa s too great to obtain reason able peak separ ation to identify individual peaks in this region. 43
made for the final readings of the absorption peaks for
.. infinite time . A plot of the data is l isted in Figure I. All rates of reaction of the four complexes were
able to be followed with little difficulty. The data for ° the 22 c runs are listed in Ta:Ole II.
The constant k2 was calculated for the four listed complexes . The reaction of m thyl iodide with the com
plexes is fir st order in rhodium (I). or iridium (I) concen
tration . The constant k gives a good fit to the expres- o b s
sion k k [MeI1 • Data used in calculation of obs = k1 + 2 k is listed in Table 2 III .
Results of the kinetics on the four l isted · complexes indicates that the iridium (!) complex reacts faster than the rhodium(I) complex , assuming_ similiar ligand types, and the o-bromophenylphosphine complex reacts faster than
the o-chlorophenylphosphine complex which in turn, reacts faster than the unsubstituted phenylpho sphine complex .
'{}ISCUSSION OF · RESULTS FOR OXIDATIVE -ADDITIDN · REACTION In that the rhodium (I) complex develops a highly
polar transition state, one closely resembling the product,
any group within the complex which is capable of electron
donation to the metal center, will lower tne ·activation
energy of the oxidative addition reaction . Electronically r
the halogen substituted ortho-phenylpho sphines should be · 4 4
2 .0-
1.5-
I - " 1 .0 -· ·-· ····•--"' '" ...... • . .. - . ·· -·· -··-·- ·- A··-· --· ·· · fil•---- .. -· ·-·· - -- -··- ··----- ·-·· -· . ·· ·· -···-····· ··- --- - ·- ·· - -- --· .. - ---- . .µ �.'. 0.5-
°' 0 M
o.o
·o .o 5.0 10.0 15 .0 20.0 2 5 .0
TIME (MINUTES)
• Carbonyl (c.hloro) bis- (dimethylphenylp.hosphin� - · ) rhodium(I) . .
b Carbonyl (chloro)bis-to�chlorophenyl (dimethyl) - phosphin ]-rhodium(!)'
o Carbonyl (chloro ) bis-(o-bromophenyl (dimethyl) phosphinej -rhodium (I)
� Carbonyl (chloro) bis- io-chlorophenyl(dimethyl)- phosp hine] -iridium(I)
Figure 1 Kinetic Data for the Oxidative Addition Reaction of Methyl Iodide and the Listed Metal Complexes at 22° C 4 5
TABLE II
DATA FOR ADDITION OF MeI TO MCl (CO) (XJ 2 ° IN TOLUENE AT 22 C
"""1 4 /1 1 0 mo. , . _ e·· a t'J..ve Rta es M -x , 1 - . k . . s.�,� l 'R 1- · 2 ---·of Re·a:ction
Rhodium PMe Ph 6.44 l.O 2 6 3 · 6 Rhodium PMe (o-ClC ff ) • 0 9 " 9 2 6 4 108 .7 Rhodium PMe (o-BrC H ) 100. 00 2 6 4 8 * ) 3 . Iridium PMe (o-ClC 6H" 4 700. 00 5 2 2
*Relative reaction rates between the rhodium (!) o-chloro- phenyl complex and th iridium (!) o-chlorophenyl complex 46
TABLE III
DATA FOR ADDITION OF MeI TO MCl(CO} tX 1 2 ° IN TOLUENE AT 2 2 C AND AT CONCENTRATION
OF Me! AS LISTED
2 .:::-1 5 -1 M ·1 0 I mol x 10 / - x 'Mer x 1 "ko '·b sec. -s Rhodium PMe Ph 18 .8 2 8.0 8 9.4 7 .. 8 2
4 . 7 7.50
Rhodium PMe (o-ClC H ) 18 .8 11 .10 2 6 4 9.4 . 6.67
4.7 5.56
Rhodium PMe (o-BrC H ) 18 .8 125.00 2 6 4 9.4 46.00
4 . 7 25.01
Irid ium PMe (o-C lC H ) 18 . 8 1880.02 2 6 � 9 . 4 260.10
4.7 150.21 47
l ess basic than the unsubstit uted ortho-phenylpho sphine , ·
since the halogens withdraw electrons from the pho sphorus 3 9 atom . The less basic a group within the complex is, the less the group will be able to donate electrons to
the metal center to lower the activation energy of the
oxidative addition reaction. The halogen substituted
ortho-phenylphosphin s shou ld be less· effective in lower-· ing the activation energy of the oxidative addition reac- tion and the relative reaction rates of the substituted phenylpho sphines should be less than the unsubstituted phenylphosphine . Ste ically , the ortho-substituted phenyl phosphines should block the approach of the methyl iodide in the oxidative add �tion reaction , more than wou ld the unsubstituted phenylphosphine . - This blocking of the metal to attack by the methyl iodide would inhibit the oxidative addition reaction , and the relati�e reaction rates of the ortho-su�stituted phenylphosphines should be less than the unsubstituted phenylphosphine .
Both the electron and steric effects of the halogen substituted ortho-phenylphosphines should retard the oxida- - tive addition reaction of methyl iodide to the complex over that of the unsubstituted phenylphosphine . A possible ex- planation to explain the contradiction in kinetic results that were ootained with that of theory, would be to suggest 48
that there is operating in the transition state, anchimeric assistance rendered by the halogen group . The halogen group should be capable of donation of electrons to the metal atom . The donation of the halogen 's lone pair of electrons to the -metal atom during the transition state would lower the activation energy of the oxidative addition reaction and would enhance he reaction rate ,
The halogens are known to participate in anchimeric assistance , or better known as neighboring group partici- pa.tion , for several well known reactions. Winstein�
Grunwald , and Ingraham measured the rates of acetolysis . . 34 of cis and trans-2-substituted cyc lohexylbrosylates . -
In the absence of neighboring group participation , cis and trans isomers would be expected , to react roughly at the same rate. The distinction between the isomers is a con- formational difference, the rates . of acetolysis of cis and trans-1,2 -dibro syloxycyclohexane differs by only a factor 3 5 of 1 . 12 . Since the conformational difference appears to be so small� the measure of the actual rate ratio of a trans isomer relative to the ·cis isomer is a rough measure of the driving force for partic ipation by the substituted
I• group . The data Winstein , Grunwald ,. and Ingraham obtained for the acetolysis of trans-2 -halocyc lohexylbrosylates are listed in Table IV. 49
TABLE IV
ACETOLYSIS RATE RATIO FOR CIS AND TRANS-2-· HALOCYCLOHEXYLBROSYLATES 34
2-sunstituent ktrans/kcis ktrans/kno participation
Clf COOH 7 C calcul ation using the 3 � 5° electrostatic approach * Cl 3 , 8 1 .. 0
Br 810.0 120 •. o
I 2 ,700, 000 .. 0 1,100, 000.0
*This value was assumed in order to calculate the one disposable parameter required �y the method used . 50
Neighboring group participation mu st be great enough
not only to overcome the low basicity of the pho sphine
ligand and the steric constraint imposed by the ortho
group, but neighboring group participation must enhanc e
the reaction rate of the complexes under· consi.deration 11
substantially enough to make the substituted phenylpho s
phine complexes more rea·ctive than the unsubstituted
phenylphosphine complex . The substituted phenylphosphine
complexes appear to have done just that , they are approxi� mately 10 to 100 ti.me s more reactive than the unsubstituted
phenylphosphine complex in the oxidative addition reaction
of methyl iod ide and the complexes.
Evidence for neighboring group participation by the
ortho-substituted phenylphosphines can sometimes be obtained
from the ultraviolet spectra of those phosphines . McEwen 44 and co-worker s reported that there is an Hextra" band
at 3 04. 5 nm in the uv spectrum of ·o-thiomethoxyphenylphos phine. McEwen and co-workers did not find an ,,. extra" band
in those phosphines wh ich were unable to provide neighbor
ing group participation in the�r reaction with alkyl halides.
The presence of an "extra" band may be indicative of intra mo lecular charge transfer absorption . The uv spectra of
the listed complexesar e given in Table V. 5 1
TABLE V
ULTRAVIOLET SPECTRA OF THE"
PHOSPHINE PMe2 R
. R "- �, ma�
Phenyl 248 nm o-Chlorophenyl 256 nm
3 2 8 nm o�Bromophenyl 250 nm
33.6 nm 52
There is an "extra" band in the ultraviolet spectrum
of both the o-chlorophenyl(dimethyl) pho sphine and the o�
bromopheny l (d imethyl) pho sphine . The.re wa s no "extra rt
band in the ultraviolet spectrum of th.e dimethylphenyl
pho sphine .
Neighboring group participation is one. explanation
to explain the relative reaction rates of the ortho-sub-
stituted phenylpho sphine complexes over that of th.e unsub
stituted phenylphosphine complex . Another explanation to explain the rate enhancement of the halogen substituted phenylpho sphines over that of the unsubstituted phenyl- phosphine deals with a steric consideration not yet dis- cussed . Increasing the size of alkyl group · attached to a 3 phosphorus atom tend s to spread the bond ang_le from p� -sp 3 toward more nearly sp hybridization , This spreading of 3 3 t h e bond ang 1 es· o f t h e p h osp h oru$ a t om f ram p -sp. t owar d s 3 sp hybr idization , increases the basic ity of the phosphoru s 3 9 atom . The o-bromo substituent is more bulky than the o-chloro substituent , and the basicity of the o-bromophenyl-
(dimethyl) phosphine should be greater than the basic ity of the o-chlorophenyl (dimethyl} phosphine . Increasing the nucleophilicity of the phosphorus atom aids in the transi- tion state of the oxidative add ition reaction and should 5.1
increase the reaction rate of the o-bromophenyl (dirnethyl) phosphine complex over that of the o-chloropheny l (dimethyl ) phosphine complex.
Another exp lanation to explain the rate enhancement of the ha logen substituted phenylpho sphines over that of the unsub st ituted phenylphosph ine deals with the HSAB principle. The HSAB princi le stand s for the Hard/Soft,
Ac id/Base principle . Ahrland , Chatt, and Davies in 1958 , classified ligands and metal ions as belong ing to one of two classes; type (al or type (bl , accord ing to their pre ·· 3g ferential bond ing . Class (a ) · metal ions include tho s e of alkali metals , alkaline earth metals , and lighter transi-
+3 tion metals in oxidation states; such as Ti · higher . + 4 , c r , +3 the hydrogen iori " Class· (b ) metal ions Fe , co+ J and Ii+. . include those of the heavier transition metals, and those
+ + 2 + 2 in lower oxidation states ; such as Cu + , Ag + , Hg , Hg , Pd
+ 2 ard her and Pt •. According to their preference tow eit class (a) or class (b ) metal ions , ligands may be classified as type (a) or type (b} , respectively. Stability of the s e
Table complexes may be swmnarized as fol lows in VI .
iti In the transition state of the oxidative add on
po sitive charge is built up on the metal reaction , a large the metal center center . The po sitive charge built up on , 54
TABLE VI
LIGAND PREFERENCE TOWARD CLASS (a) OR
CLASS C_b ). METAL IONS
Tendency to Complex Wi'15h , Tendency to· Complex Wi'th c1·ass (b ) . Meta--i· ·cat Meta-i- To-ns "Cla:ss Ions
>As)Sb N)) P> As> Sb N(( P
O<< S< Se A1 Te O)_) S > Se .) Te
F:> Cl ) Br ) I F< Cl makes the metal a soft acid center . The tendency of a soft base ligand to complex with a soft acid center is Br ) Cl . The complexing of the halog.en to the metal center lowers the activation energy of the oxidative addition reaction� by donating electrons to the developing positive metal center in the transition state . Si.nee the bromine- metal compl ex is a stro�ger complex than the chlorine metal complex, oromine will enhance to a greater extent the reaction rate of the oxidative addition reaction , over that of chlor ine . DISCUSSION OF INFRARED SPECTRA The activity of a catalyst in the oxidative addition reaction is determined by the electronic and steric effects of the ligand s attached to the .metal complex . A parameter which is used to determine the relative basicity of a given (I } phosphine ligand for a comp lex of. the type Rh Cl CCO} (PR3 ) 2, is the value of from the infrared spectrum of the com- . i co The lower the value of for a given complex , plex . � co the greater is the nucleophilic ity of the phosphine ligand . The obta ined for each of the complexes are _ .. listed . in i co Table VII. The obtained for each of the complexes, � co ind icates that the dimethylphenylphosphine is more basic than the halogen ortho-substituted phenylphosphines , By induction , the halogens withdraw electrons from the 5 6 TABLE VII the Complex � co for I H (C J ] Rh Cl (C O} [.(o-xc6 4 J. H3 2P 2 - -x "- � co . -1 H 194 5 and 1 960 cm -1 Cl 1955 and 1 970 cm -1 Br 2000 and 2050 cm 57 phosphorus atom . The withdrawing of electrons from the phosphorus atom , makes the substituted phenylpho sphine s less basic than the unsubstituted phenylphosphine _ A problem arises when comparing the for the bromo and . � co chloro ortho-substituted phenylphosphine complexes, The chlorine atom is more electronegative than the bromine atom , the dipole -moment of chlorobenzene is 1�6 and for ' 1 4 3 b romo b enzene, the d ipo� 1 e moment is. • 5 • The electron withdrawing tendency of chlorine as compared with that of bromine , indicates that for the . phosphines, the o-chloro- phenyldimethylphosphine should be less basic than o-brorno phenyl (dimethyl) phosphine . Induction is not the only effect in operation in the substituted phenylpho sphine sy stem . Brown 45 , observed that a direct conjugation effect operates in the so lvolysis of cumyl chloride in 90% aqueous acetone. All rates are relative ·to the parent molecule (k for H) , and in aqueous acetone • 0 x + (' 90% C-4 . 62) With r so chosen , 6+ values for the substituted cumyl chlor ide can then be der ived ; 0 , .112, 6 � = 6 �l = 0 (X = H, Cl, Br) values of the substituents to the Comparing 6+ � co values of the complexes , an indication that an increase in correspond to an increase in + value becomes '3 co ( 58 apparent � That is , an increase in correlates wi th a �co decrease in the. aoility of the phosphine ligand to stabi lize the po sitive charge on the metal. center � The ability of the phosphine l �gand to stabilize a positive charge on the metal center is dependent on the basicity of the sub stituents incorporated in the make-up of the pho sphine ligand . The basicity of the three substituents are H> Cl'> Br . The decrease in for the complexes Br·) Cl> H is � co consistent with the increase in bas.icity of the phosphine ligand s Br < Cl < H. A decrease in the ability of the phos- phine ligand to stabilize the pqsitive charge on the metal center causes the other ligand s on the metal center to ac- cept a greater role in the delocalization of the po sitive charge . The carbon monoxide ligand to the metal bond be- comes weaker as the carbon monoxide helps to delocalize more of the pos itive charge qf the metal , and the carbon- oxygen bond becomes stronger resulting in an increase in the value for the complex . 4 co . Thus in the oxidative addition reaction, anchimeric assistance by the halogens overrides the decrease in the basic ity of the halogen substituted phosphine . ligand s and causes the actual rate orders to increase H < Cl < Br , while basicity of the substituents actually decreases H> Cl) Br 4 5 9 1 There are two major peaks in the ra�ge 1900 to 2 100 cm in the infrared spectrum for the complexes listed . Deeming 36 and Sharratt studied infrared spectra of a number of solu tions of Rh c 1 cco 1 in cyclohexane with successive additions 2 2 4 of PMe Ph.. They observed that there were present a number 2 of peaks which gradually were replac ed wi th one single peak as the ratio of PMe Ph/Rh c1 (co} was increased to a maxi 2 2 2 4 mum of 2 .11. Deeming and Sharratt sugges ted a series of reactions to ac ount fo these peaks. +L Rh Cl {_CO l - �Rh Cl (CO ) L Rh Cl (C0 ). L ) 2 2 4 o 2 2 3 �o) 2 2 2 2 2 RhCl (CO) L or 2 +2L +2L > RhCl (C0) L � 2 RhCl (CO) L 2 2 . _2CO 2 The presence of peaks could be due to isomers at equilibrium, possibly the cis-isomer which would have two peaks lying above the one peak for the trans-isomer . Another possibil ity to explain the presence of mu ltiple peaks is that the complex exists as a dimer [RhCl (CO) . (PMe P h) . Either of 2 2 ) 2 these explanations cou ld explain the presence of mu ltiple peaks for the complexes, the suggestion of a di.mer of the complex being the most likely explanation . IRIDIUM vs RHODIUM COMPLEX The oxidative addition reaction of methyl iodide with an iridium (Il complex as compared to a rhodium (I) comp lex of like structural make-up conforms with known order s of 6 0 8 16 reac tivity of d tran sition metal compl exes . rr1cl (CO) 2 Co -ClC R 2P) 2 complex reacted 5'8 . times faster than ( 6 4 l. (CH.3l I the Rh Cl (C O) ( (o -ClC H 1 (CH } 2P] 2 complex . 6 4 3 CARBONYLATION 'KINETICS Th e relat ive reaction rates for the carbonylation of methano l in the presenc e of various rhodium complexes and methyl iodide promoter , were not as dr amatic as the relative reaction rate increases for the oxidative addition reaction of methyl iodide and the same complexes .. The data is listed in Table VIII.. The data indicates the same order of reactiv- ity for the respective complexes , in the carbonylation reac tion of methyl iodide , as was pbtained from the oxidative I addition kinet ics : Rh Cl (CO) ( Co-XC H ) (CH )2P) 2� X = H, Cl , 6 4 3 Br (Br > Cl) H) . ( 61 TABLE VI II DATA FOR THE CARBONYLAT I'ON OF MeOH ° IN ACETOPHENONE AT 165 C IN THE PRESENCE OF METHYL IODIDE PROMOTER ,. ;Rhcl •3H o, AN D THE 3 2 INDICATED PHOSPHINE LIGAND ADDED 2 Phosph ine L� 'j_1mrtol CO/s ec ) x' '1'0 " Rela·tiVe Re·action ""Rates no ligand added 3. 68 . 0.45 8.15 1.00 PMe2Ph added PMe (o-ClC H } added 11 . 2 7 1. 38 2 6 4 PMe (o-BrC H 1 added 12 .50 1.53 2 6 4 . 62 3 . 0- 2.0- LO-· o.o 2 0.0 40.0 60.0 TIME .(MINUTES) • • RUN No Phosphine Added , RhC1 3H 0 I 3 _ 2 RUN PMe Ph Added , RhC1 ·3H 0 A II 2 3 2 RUN PMe (o�ClC H ) Added , Rhc1 ·3H O a III 2 6 4 3 Z PMe (0-Br� H ) Added , RhC1 ·3H 0 M RUN IV 2 6 4 3 i Figu re II Kinet ic Data for the Carbonylation Reaction of Methanol in the Presence of Methyl Iodide Promoter and Phosphine-Metal. System Listed at 165° c 63 SUMMARY Kinetic studies of rhodium and iridium systems were made for the oxidative addition reaction and the carbonylation reaction. [o -Chlo�ophenyl (dimethyl} - pho sphine] --rhodium C.I1 complex reacted 9" 9 times faster than the (dimethylphenylphosphineJ -rhodimn(I) complex in an oxidative addition reaction of methyl iod ide and the listed complexes. fo -Bromophenyl (d imethyl} phosphine1 - rhodium (Il complex reacted 11_0 times faster than the [o-chlorophenyl (dimethyl) phosphine1 -rhodium (I) complex and 108.7 times faster than the (d imethylphenylpho sphine) rhodium (IJ complex . The (o-chlorophenyl (dimethyl )phos phinel -ir idium (I) complex reacted 58 .2 times faster than the [o -chlorophenyl (dimethyl) phosphine] -rhod ium(I) com- plex . All of the above relative reaction rates cited were for the oxidative addition of methyl iodide and the listed complexes. The carbonylation of methano l in the presence of methyl iodide promoter and metal complex showed less an increase in relative reaction rates for the oxida- tive addition reaction of methyl iodide and the same com plexes. ro -Chlorophenyl (dimethyl) phosphine) -rhodium ( I} complex reacted 1.3 8 times faster than the ld imethylphenyl complex . The o-oromophenyl (d imethyl) - phosphine) -rhodium(I ) l 1.53 times as fast as phosphine) -rhodium complex reacted · 64 did the raimethylphenylpho sphinel -rhodium (I ) complex . The kinetic results for the ox idative ·addition reaction and the carbonylation reaction carried out both indicate that neigh.Doring group partic ipa.t ion by the halogen of the ortho- suo stituted phenyl (dimethyl }pho sphine ligand is responsible for the enhancement in relative reaction rates for those comp lexes which contained those halogen containing ligands. Complexes which did not contain any group capable of neighboring group partic ipation were unable to provide enhancement in relative react ion rates and were less reactive i� either the oxidative addition reaction of methyl iodide or the carbonylat ion of methyl iodide Q 65 APPENDIX -1 The infrared absorpt_ion· spectra ar e listed in cm with their relative intensities as follows : w weak m - medium s - strong shld. - shoulder The potassium bromide used in obtaining the spectra showed -1 -1 two bands 3420 cm and 1630 cm whi ch presurnab�y were due to the presence of wat er 66 Table I. Infrared Absorption Maxima for o-Bromophenyl (dichloro )phosphine · . - 1 -1 Wave Number(cm ) Intensity Wave Number { cm ) s i y Inten t 3060 w 1250 w 3030 shld . 1115 s 2950 s 1070 m . 2920 shld . 1010 m 2860 s 985 w 2795 shld . 975 w 159 5 w 940 m 1485 w 885 w 1460 shld. 870 w 1�45 s 815 m 1435 shld . 77 0 s 1365 w 740 s 1320 shld . 725 shld . 700 s 1310 shld . 650 s 1285 s 1263 w Infrared spectrum wa s obtained _neat on a sodium chioride plate . . 67 Table II . Infrared Absorpt ion Maxima for o-Bromophenyl( dimethyl )phosphine . -1 -1 Wave Number(cm ) Intensity Wave Number(cm ) Intensity 3060 w 1263 w 3030 w 1115 s 2960 shld . 1010· m 2930 s 1010 m 2860 s 965 m 2795 shld·. 940 w 1595 w 920 shld . 1485 m 907 m shld . w 1470 840 1460 m 810 w 1445 m 780 m 1435 m 740 s· 1375 m 700 s m 685 shld . 1300 1285 m 650 . m Infrared spectrum was Obta1·ned neat on a sodium chloride plate. 68 Table III. Infrared Absorption Maxima for Carbonyl( chloro )bis-lo-bromophenyl- (dimethyl) phosphinel -rhodium(I). -1 - Wave Number(cm ) Intensity Wave Number(cm 1 ) Intensity 3440 m 1220 s 2925 s 1100 m 2850 s 1060 m 2050 s 1005 s 2000 s 910 s 181 5 m 780 m m 1595 m 745 1440 m 695 m 1400 m 650 m Infrared spectrum was obtained us ing a potass ium bromide pellet . 69 Table IV . Infrared Absorption -Maxima for o-Chlorop henyl(dichloro } phosphine . Wave -1 -1 · Number(cm ) Intensity Wave Number(cm ) Intensity 3050 w 1115 shld . s 2950 110 5 m 2920 shld . 1070 w 1580 m 1035 shld . 1560 m 1020 s 975 ·1450 m m 143 5 s 800 w 1305 w 755 s m 730 m 1280 1255 m 710 w 1130 m 660 s Infrared spectru� was obtained neat on a sodium chloride plate . 70 Table V. Infrared Absorption Maxima for o-Chlorophenyl( dimethyl )phosphine .. . -1 . Wave Number(cm ) -1 Int ensity Wave Number( cm ) Intensity 3060 m 1060 s 2960 s 1035 s 2900 s 995 w 2870 h . s ld 975 w 945 1580 m s 1560 m 900 s 870 m 1455 s 1430 s 820 m shld . shld . 1420 800 129 5 m 750 s 1275 m 730 s 1250 m 710 s 1130 m 665 m 1110 m 650 s Infrared spectrum was obtained neat on a sodium chloride plate . 71 Table VI. Infrared Absorption Maxima for Carbonyl (chloro )bis-l o -chlorophenyl- (dimethyl )phosphineJ -rhodium(I). -1 Wave Number(crn ) Intensity Wave Nubrner(cm -1 ) Intensity 3060 shld . 1110 shld .. 2960 s 1065 w 2900 s 1035 s 1970 s 995 w 1955 945 s s 1 580 m 900 s 1565 m 865 rn 1450 s 840 m 0 1430 shld . 80 shld . s 760" . 1420 shld 750 1295 m s 7 0 1285_ s 3 s 1250 s 705 m 1160 m 690 s s 650 m 1130 Infrared spectrum was . obtained using a potassium bromide pellet . 72 Table VII. Infrared Absorption . Maxima for Dichlorophenylphosphine . -1 Wave Number(cm ) Intensity Wave Number(cm -1 ) Intens ity 3070 . shld 1110 shld . 3050 m 1090 s 1585 m 1070 m 1480 m 1025 w 1435 s 1000 w 1380 w 920 w 1330 w 845 w 1300 w 785 shld . 1275 s 745 s 1260 shld . 720 m . 685 s 1225 shld 1185 w 670 m 1160 w Infrared spectrum was obtained.neat on a sodium chloride plate . 73 Table VIII . Infrared Absorption Maxima for Dimethylphenylphosphine . - 1 -1 Wave Number(cm ) Intensity Wave . Number(cm ) Intensity 3070 m 1075 rn 3055 m 1030 m 2960 s 1005 m 2900 s 945 s 2810 m 915 shld . 1585 w 900 s 1485 m 865 s 1435 s 820 w m 785 1295 w 1280 m 745 s 1195 m 715. shld . 1160 w 695 s 1120 shld... 665 m 1110 m Infrared spectrum was obtained neat on a sodium chloride plate . 74 Table IX . Infrared Absorpt ion Maxima for Carbonyl( chloro )bis-ldimethylphenyl- phosphin�l-rhodium( I). -1 -1 Wave Number (cm ) Intens ity Wave Number( cm ) Intensity 3075 m 1105 rn 3050 m 1075 w 2960 m 1030 w 2900 m 1005 w 1960 s 945 s s 925 shld . 1945 1575 m 910 s 1555 m 875 m shld . m 1435 850 785 w 1420 w 1295 m 745 s 1280 m 715 m 1190 w 695 m 1160 w 680 m 1135 w Infrared spectrum was obtained us ing a potassium bromide pellet . ·75 Table X. Infrared Absorption Maxima for Carbonyl( chloro )bis-\o-chlorophenyl- (dimethyl )phosphine) -iridiurn(I). -1 -1 Wave Number(cm ) Intensity Wave Number(c m ) Intensity ' 3080 w 1160 shld. 2960 m 1125 s 2905 · m 1110 s 2010 m 1060 w 1995 m · 1035 s 1545 rn 950 m 1460 m 910 s 1420 m 865 w 1400 shld • . 800 rn 1290 m 750 s 1250 m 705 m Infrared spe.ctrum was obtained using .a. potassium bromide pellet • .. 76 TABLE XI . Nuclear Magnetic Resonance Chemical Shift (Chemical Shifts Relative to TMS , External) o-Chlorophenyl(dichloro)phosphine. Chemical Shift, ppm to (m, 4H) 7.37 7 � 82 o-Chlorophenyl (dimethyl)phosphine. Chemical Shift, ppm Coupling Constant, Hz 7.50 to 7.95 (m, 4H (d, 6H) = H 3.07 J 8 z Dichlorophenylphosphine. Chemical Shift, ppm to (m, SH) 7 . 20 8.15 77 TABLE XI (con't) Dimethylphenylphosphine. Chemical Shift, Coupling Constant , H ppm z 7.00 to 7.95 (m, SH) (d, 6H) = H 1.95 J 7 z 78 TABLE XII Mass Spectrum of Carbonyl(chloro)bis-[dimethylphenylpho sphine]- rhodium(I) . 442 amu molecular ion 414 am.u loss of C=O 379 amu loss of C=O and Cl . 365 loss of C H - 6 5 330 loss of c H - and Cl 6 5 304 loss of (c u )(CH ) P- 6 5 3 2 302 loss of c H -, Cl, and C=O 6 5 288 loss of· two c H - 6 5 ------·- 79 TABLE XIII Mass Spectrum for Carbonyl (chloro)bis-'LO-chlorophenyl (dimethyl)- phosphine ] iridium(!) . 600 amu molecular ion · 48 9 loss of o-ClC H - 6 4 428 amu loss of o-ClC H (cH ) P- 6 4 3 2 42 6 amu loss of o-ClC H -, Cl, and C=O 6 4 400 amu loss of (o-ClC H )(CH ) P- and C=O 6 4 3 2 365 amu loss of (o-C lC H )(CH ) P-, Cl, and C=O G 4 3 2 350 amu loss of two o-c1c H - and C=O 6 4 282 amu loss of o-Cl H - , (o-ClC H )(CH ) P-, �6 4 6 4 3 2 and Cl amu loss of (CH ) 288 (o-ClC6H4 ) 3 2P-, C=O ,- and o-ClC H - 6 4 . - . · · · :... -...-,. - --· -..·- �·- .. · - - ---�···..,,,_...--· - ..- -. - -- - •· . -- �- .. - 80 TABLE XIV Mass Spectrum for Carbonyl {chloro )bis- (o-brornophenyl (dimethyl) phosphineJ rhodium (!) 602 amu molecular ion 493 amu loss of Br and C=O 416 amu loss of o-BrC H - and C=O 6 4 352 amu loss of (o-BrC H )(CH ) P- and C=O 6 4 3 2 349 amu loss of (o-BrC H )(CH ) P- and Cl 6 4 3 2 32 6 amu loss of o-BrC H - , Br , and 6 4 Cl 302 amu loss of (o-BrC H )(CH ) P- and Br 6 4 3 2 277 loss of {o-BrG H )(CH ) P- , Br, and C=O amu 6 4 3 2 81 TABLE XV Mass Spectrum for Carbonyl (chloro)bis-(o -chloro (dimethyl) - p.ho sphine ] rhodium(!) 510 amu molecular ion 482 amu loss of C=O 47 5 amu loss of �l 308 amu loss of (o-ClC H )(CH ) P- and C=O 6 4 3 2 301 amu loss of (o-ClC H )(CH ) P- and Cl 6 4 3 2 274 amu loss of (o-C lC H )(CH ) P-, and C=O 6 4 3 2 Cl , 235 amu loss of (o-ClC H )(CH ) P-, two Cl, and C=O 6 4 3 2 213 amu loss of (o-ClC H )(CH ) P-, o-ClC H -, and 6 4 3 2 6 4 C=O ···-·--·--- - - ..----·- ---· --"-·.._-- .. - - - .. -...... --·· .. - - --- ;�-- ..· ·�-·-··-�:..,...... ____ _ I:"'•· � · � · ·· · . . . � . ;·u·--- ��� ·• . 8 2 BIBLIOGRAPHY c.w. 1. 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