NATURE AND REACTIONS OP THE COMPLEXES OP NICKEL,
PALLADIUM, AND PLATINUM WITH 2-PYRTDTNA LDOXIME
AND DIMETHYLGLYOXIME
DISSERTATION
Presented In Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of the Ohio State Uhlversity
By
RONALD ALFRED KRAUSE, B. Sc.
*******
The Ohio State University
1959
Approved by
Adviser Department of Chemistry ACKNOWLEDGMENTS
It is with extreme pleasure that the author wishes
to thank Dr. Daryle H. Busch for his council, encouragement,
and enthusiasm which made the years in graduate school
meaningful. To Dr. Quentin Van Winkle the author is very
grateful for suggestions and the use of the ultracentrifuge both of which were extremely helpful in the completion of
some of these investigations. The author wishes to thank
Dr. Sheldon G. Shore and Mr. Selwyn H. Rosenthal for kindly
providing the use of their dry box, necessary in a portion
of this work. Dr. Melvin L. Morris, Mr. Donald C. Jicha,
and Mr. William R. Findley are to be thanked for obtaining
all the infrared spectra reported in this dissertation; Mr.!
Jicha is also to be thanked for supplying one of the
compounds used for comparison. The National Institutes of Health is to be thanked for a Research Fellowship
supporting the author during the latter part of the work
reported herein. Mrs. Robert Holsinger, Jr. prepared the
drawings and Mrs. Leo Moore typed the dissertation; the
author is grateful to them for these services. And above
all the author wishes to thank his wife, Kay, not only for typing the first draft of the dissertation but for her help and encouragement during the years at The Ohio State
University. CONTENTS
Chapter Page I. 2-PYRIDINALD0XIME COMPLEXES OP NICKEL(ll), PALLADIUM(II) , AND PLATINUM(II) ...... 1
A. Introduction...... 1 1. Complexes of o£-DIoximes ..... 3 2. Complexes of 2,2 -Bipyridine . . . 15 3. Complexes of Bidentate Amine Oximes 16
B. Experimental ...... 18 1. Preparation of L i g a n d ...... 18 2. Nickel C o m p o u n d s ...... 19 3. Palladium and Platinum Compounds . 25 4. Physical Measurements...... 27
C. Results and D i s c u s s i o n ...... 28 1. Nickel(ll) Complexes ...... 29 2. Palladium(ll) and Platinum(ll) Complexes ...... 44
D. Discussion of Infrared Spectra .... 47
II. REACTIONS OP NICKEL(il), PALLADIUM(II), AND PLATINUM(II) COMPLEXES OP 2-FYRTD1NAL- DOXIME AND DIMETHYLGLYOXIME...... 85
A. Introduction...... 85 1. Reactions of Coordinated Ligand . . 86 2. Reactions of the Central Metal Atom with Halogens...... 87
B. Experimental ...... 93 1. Preparation of Dimethylglyoxime Complexes...... 93 2. Reaction of 2-Pyridinaldoxime Complexes with B r o m i n e ...... 95 3. Reaction of Dimethylglyoxlme Complexes with B r o m i n e ...... 97 4. Reaction of Complexes with Reagents Containing an Active Halogen ...... 99 5. Physical Methods ...... 103
C. Results and Discussion ...... 104 1. Reactions with Compounds Containing Active Halogen ...... 106 2. Reactions with B r o m i n e ...... 109 ill ♦ iv
CONTENTS (Contd.)
Chapter Page
III. SUMMARY...... 116 APPENDIXES
I. Magnetic Susceptibility Measurements ...... 122
II. Temperature Dependence of the Magnetic Susceptibility of [Nl(P0X)2 ] 127 III. Infrared Absorption Spectra of the Nickel(il), Palladium(II), Platinum(ll), and Platlnum(IV) Complexes of Dimethylglyoxime ...... 129
BIBLIOGRAPHY...... 139
AUTOBIOGRAPHY...... 1^5 LIST OP TABLES
Table Page
1. The Use of Nickel Derivatives in the Confirmation of Oximes ...... 4
2. Magnetic Moments and Conductivities of Complexes of 2-Pyridinaldoxime ...... 3 0
3. infrared Absorption Spectra and Assignments for Complexes of 2-Pyridinaldoxime. Complexes Containing Unionized Ligand...... 4 9
4. infrared Absorption Bands and Assignments for Complexes of 2-Pyridinaldoxime. Complexes Having One Ligand Proton Ionized ...... 56
5. Infrared Absorption Spectra and Assignments for Complexes of 2-Pyridinaldoxime. Uncharged Complexes ...... 61
6 . Infrared Absorption Spectra and Assignments for Complexes of 2-Pyridinaldoxime. Reaction Products...... 67
7. Magnetic Susceptibilities of Nickel(il) Complexes of2-Pyridinaldoxime ...... 125 8 . Standardization of Magnetic Susceptibility Apparatus...... 126
9. Temperature Dependence of the Magnetic Susceptibility of [Ni(P0X)2 ] ...... 128
10. Infrared Absorption Spectra of Nickel,. Palladium, and Platinum Complexes of Dimethyl- glyoxime ...... 130
v LIST OP FIGURES
Figure Page p 1. Configurations of d° Ions, Their Magnetic Moments, and Their Crystal Field Splittings . . 11
2. Job Method of Continuous Variations, [Ni(POX)(HPOX)]I and AgNO^ ...... 35
3. Ultraviolet Absorption Spectrum of Ni(P0X)2HI Solutions and Their Interaction with Silver Ion 37
4. Temperature Dependence of Magnetic Susceptibility of [Ni(P0X)2 ] 42
5. System Pd++ -HPOX, Titrated with N a O H ...... 46
6 . Infrared Absorption Spectrum of HPOX and of [Ni(HP0X)3 ]l2 .2H20 . 53
7. Infrared Absorption Spectrum of [Ni(HP0X)oIo ] and [NI(HP0X)2C12] ...... 54
8 . Infrared Absorption Spectrum of [Ni(HPOX)o (CH3COO)2 ] and [Ni(POX)(HPOX)(CH3COO)(HgOfi. . . 55
9. Infrared Absorption Spectrum of [Ni(POX)(HPOX)(py)2 ]I and [Ni(POX)(HPOX)Jl . . 59
10. Infrared Absorption Spectrum of [Pd(POX) (HPOX) ]C1 60
1 1 . Infrared Absorption Spectrum of [Ni(P0X)opy] and [Ni(P0X)2 (py)2 ] ...... 64
12. Infrared Absorption Spectrum of [NifPOX)^] and [Pd(P0X)2 ] i . . . 65
13. Infrared Absorption Spectrum of [Pt(P0X)2 ]. . . 66
14. Infrared Absorption Spectrum of [Pt(P0X)2Br2 ] . 71
15. Infrared Absorption Spectrum of [Pd(P0X)2Br9 3 and of [Pd(P0X)2 ] and Br2 Reaction Product. . . 72
16. Infrared Absorption Spectrum of [Pd(P0X-C0CH3 )Cl2 ] and [Pd(P0X)Cl]2 ...... 73
vl vii
LIST OP FIGURES (Contd.)
Figure Page
17. Infrared Absorption Spectrum of [Pt(P0X-C0CH3 )2 ]Cl2...... 74 18. Infrared Absorption Spectrum of [Pd(POX-COCgH5 )Cl23...... 75
19. Infrared Absorption Spectrum of[Pd(DMG)0 ] and [Pt(DMG)2] ...... d . . 133 20. Infrared Absorption Spectrum of [Pt(DMG)2Br2] ...... 134 21. Infrared Absorption Spectrum of CHC1- In soluble Product of Reaction of [Nl(DMG)2 ] and BrP and Infrared Absorption Spectrum of [Ni(HJMJ)2Br2 ]...... 135 22. Infrared Absorption Spectrum of [Pt(HDMG)Cl2 ] and [ Pd(HDMG)Br2 ] ...... 136
23. Infrared Absorption Spectrum ofNi (HDMSjCl^I^O 137 I. 2-PYRIDINALDOXIME COMPLEXES OP NICKEL(II),
PALLADIUM(II), AND PLATINUM(II).
A. Introduction
The nickel(II), palladium(ll), and platinum(ll) complexes of 2-pyridinaldoxime (HPOX) (structure I) are the subject of this section of the dissertation.
2-Pyridinaldoxime was first prepared by Lenart1 in 1914 (as a derivative of the aldehyde), but no attempt was made to prepare its complexes. 2-Pyridinaldoxime shows structural features of both dimethylglyoxime (HDMGr)
h 3c OH- \ / J c c
HO—N// \ N-OH ■N 'N
II III
(structure II) and 2,2'-bipyridlne (bipy) (structure III), in that it has an oxime function to a second donor group (as in HDMG), and in that the second donor group is a
2-substituted pyridine ring, such as exists in 2 ,2 *-
bipyridine.
2-Pyridinaldoxime also shows some similarity to
2-methyl-2-amino-3-butanone oxime (AOH) (structure IV)
C H, CHcj n r- -Clio // r H 0— N NH2
IV in that both compounds are amine oximes, the amine in
one being aromatic, that in the other, aliphatic. This
amine oxime can be considered as a composite of HDMG
(structure II) and ethylenediamine (en) (structure V).
H o C CH0 *7 h 2 n n h 2
V
Two ligands similar to 2-pyridinaldoxime, and some of their complexes, have been reported. Tschugaeff2 first prepared palladium(II) and platinum(II) compounds of phenyl-fit-pyridyl ketoxime (structure VI); Sen, recently, reported the use of this ligand for the spectro- 3 4 photometric determination of palladium(ll). Emmert and Diehl-* reported the reaction of methyl-^C-pyridyl ketoxime (structure VII) with nickel(ll). Both of these ligands have been studied only in a cursory manner. The
investigation of the complexes of HPOX reported in this
,c 6h5 / 6 5 / k3 V / 0H S * / 0H
VI VII dissertation represents the first detailed study of a
ligand of this class. The only experimental work which
has been reported on complexes of HPOX Involves the
equilibria of the iron(ll) derivatives in aqueous solution^
1. Complexes of qt-Dioximes.— Since Tschugaeff dis
covered the complexes of o^-dioxinies, ^ the interaction of
oximes with metal Ions has been of considerable interest
to chemists. Tschugaeff also discovered the bright red
compound [Ni(DMG)2 ] and published the first paper O utilizing it for the quantitative determination of nickel.
Since Tschugaeff*s time the nickel, palladium, and plati num complexes of many oximes have been studied. Organic
chemists have utilized color reactions with nickel to
confirm the nature of oxime derivatives (Table l).
Analytical chemists have used oximes as reagents for the determination of nickel, palladium, and platinum, and inorganic chemists have studied the structures and re actions of these Interesting compounds. Unfortunately TABLE 1
THE USE OP NICKEL DERIVATIVES IN THE CONFIRMATION OP OXIMES
Ligand Complex Color Reference
Nitrosoguanidine dark red Thiele, Ann. Chem.. Liebigs, 273, 133(1893)
Phenylbenzyldiketone orange-red A.lello, Gazz. chim. ital.. 67. 444(1937). dioxime
Cyclohexanedione dioxime violet red Jaeger and Bi.lkerk, Proc. Acad. Sci. Amsterdam. 40. 12(1937. 3-Me thy1-4-pyruvy1fura zan scarlet Ajello and Cusmano, Gazz. chim. ital., 69. dioxime 391(1938).
Phenyl-methyl- yellow to Ajello and Cusmano, Gazz. chim. itaL. 70. pyruvyltrlazole orange 770(1940).
Phenyl-methylglyoxlme, Hartung and Poster, J. Am. Pharm. Assoc., P-NOg colored 22, 15(1946). p-NHAc colored p-NHBz colored
Diacetyl oxime brown-red Hovorka and Holzbecher, Collection Czech. thiosemlcarbazone Chem. Communs.. 16. 437(1960).
4-Methylpent-3-ene- red Kuhn and Trischmann, Ann., 573, 55(1951). 1,2-dioxime
Methylethyl glyoxime --- Schotte, Acta Chem. Scand.. 5. 969(1951). TABLE 1 (Contd.)
Ligand Complex Color Reference p-Toluidinohino-purpurin black Nozoe, Ebine, Ito and Takasu, Proc. Japan dioxime Acad., 21, 197(1951). p-Nitrophenylglyoxime brown-red Musante and Parrini, Gazz. chim. ital., 81, 451(1951). Methyl-Iso-propyl- yellow Milone and Borello, Gazz. chim. Ital.. 8 5 , glyoxime 495(1955). Me thy1ethyIglyoxime red and yellow
VJl the latter studies, those concerned with structure and reactivity, have not been as extensive as the others.
Of all the oxime complexes, Tschugaeff's compound,
[Ni(DMG)2 ], has been the most studied. Three isomers of ffcdioximes are possible (structures VIII - X).
R R Rv R R . R \c c / \ c ------c / \ 'c ------c / // \\ // w ^ ^ N. M N N N HO OH HO HO OH H(T
anti amphl svn
VIII IX X
Tschugaeff^*^ was the first to show that only the anti form (at that time called the syn form) is capable of forming characteristic complexes. Since that time, the reaction of nickel(il) with oximes has been used to de termine the isomer of the oxime under consideration,1®*11 and nickel(il) has been used to separate oxime Isomers.12
For many years the structure of [Ni(DMG)2 ] was unknown and a topic of considerable Interest. S u g d e n 1 ^ was the first worker to isolate els and trans Isomers of a four-coordinate nickel(il) complex, and consequently establish the square planar configuration. The complexes prepared were those of benzylmethylglyoxime (structures
XI and XII). Cis-trans isomerism would be Impossible in a regular tetrahedral structure. The similar dimethyl-
glyoxime complex, [Ni(DMG)2 l, would almost certainly
h3^ / 6 h 5 H3<\ /C6H5 C CN p --- .o -n ' Jto-a jd-n C ^ n - o v H;' Ni^ '.H H< Ni 'H '0-1^ ^ - 0’’ '0- N ^
h3cr \ - C6H5 H5C6 CHc
els trans
XI XII have the same configuration, in this case, planar. Cambi 14 and Coriselli measured the magnetic susceptibility of
[Ni(DMG)2 ] and found this compound to be essentially diamagnetic (-^eff = °*3^ Bohr Magnetons). This is very good evidence for the square planar configuration, which requires the dsp2 bonding of the valence bond theory.
Rundle and Parasol,^ from a study of the infrared ab sorption spectrum of [Ni(DMG)2 ], suggested the presence of a symmetrical hydrogen bond (structure Xlll) and Yaraada
H,C CHo 3 \ / 3
%-Ot. H" III H
N> - ° / H3Cy — 4 ch3
XIII and Tsuchida suggested metal-metal interaction in the
solid state on the basis of dichroism measurements per
formed on [Ni(DMG)2 3 and [Pt(DMG)2 3, while Pech, Polster,
and Rezabek-*-? used x-ray measurements to prove the
isomorphism of [Ni(DMG)23, [ Pd(DMG )2], and [Pt(DMG)2 3. XS Finally, Godycki and Rundle determined the complete
structure of [Ni(DMG)2] by the use of x-rays. Their findings indicated that nickel is in a planar configu ration (structure XIII). They observed that the mole cules are so stacked that the nickel atoms are aligned along an axis, one above the other, and the distance between nickel atoms along this axis is relatively short.
They postulated that the first excited state is an octa hedral structure, derived by promoting one 3d electron to the ^p level and forming nickel-nickel bonds. A small contribution of this type would stabilize the particular packing noted In the crystal, and contribute greatly to the insolubility of this material.
These authors also make note of the short dis tance between opposing oxime oxygens, and mention the sym metrical hydrogen bond proposed earlier.Recently, how ever, Blinc and Hadzi,^ after studying the infrared spectra of [Ni(DMG)2], [Pd(DMG)23, and [Pt(DMG)2 3 in ad dition to the spectra of several other compounds, claimed that the hydrogen bonds are not symmetrical. 20 Workers in this laboratory have come to feel
that hydrogen bridges, if existent, are a consequence
and not a cause of stable complex formation. It is
probably best to depict [Ni(DMG)p] (structure XIII) with 21 unsymmetrical hydrogen bonds. Indeed, Thilo and Friedrich
H0C- .
XIV have shown that the monomethyl ether of HDMG (HDMe)
(structure XIV) is capable of forming complexes with nickel(II) which are similar to those of HDMG. In an uncharged complex with HDMe, [Ni(DMe)2 l, there could be no hydrogen bonding. Consequently, the hydrogen bridge
seems to be of relatively slight importance in the for mation of these compounds.
The characteristic reaction of nickel(II), palladium(II), and platinum(ll) with most oximes appears to be the precipitation of nonionic species, of the type
[ML2 ] (which has just been described), from aqueous solution with the charge being neutralized by the loss of two oxime protons. These compounds in general are diamagnetic, indicating a planar configuration about the metal ion as in structure XIII, which may be described 10
in terms of the valence bond theory as utilizing dsp2
bonding. (See Figure 1 for a brief summary of geometrical
configurations, bond hybrids, magnetic moments, and
crystal field energy splittings for d® ions.) The com
pounds [Ni(DMG)2 ], [Pd(DMG)2], and [Pt(DMG)2] are quite
stable, and their insolubility in water makes them of
analytical importance.
A second class of complexes with this ligand has
been prepared. These compounds exhibit a one to one
ratio of HDMG to metal and contain coordinated halide.
[Ni(HDMG)Cl2 ] has been prepared by Paneth and Thilo22 and
also by Dubsky and Brychta;2^ the latter authors also pre
pared [Ni(HDMG)Br2]. The compound [Pd(HDMG)C12 ] has been
prepared by Sharpe and Wakefield,2 ^ and [Pt(HDMG)Cl2 ] has
been prepared in the work reported here. The nickel(IT)
complex, [Ni(HDMG)Cl2], is unstable in water, precipi
tating the red complex, [Ni(DMG)2 ] according to the
equation
2 [Ni(HDMG)Cl2 ] [Ni(DMG)2 ] + N i ^ + 2H+ + 4C1'
The palladium and platinum compounds undoubtedly exist in p = 3.2 - 4 2 BM sp9 sp9 bonding Tetrahedral ^ i ay* i h A A 1 1 / ^ p * 2.9 - 3.2 B.M. tp*d* bonding Octahedral *y « t ENERGY ENERGY LEVEL DIAGRAM - ,8 d --- «**» ®yz «**» d,t^£
il Configurotiont of d* Ions, -Their Mognetic Moment*, ond Their Crystol Fieid Splittings d df« , d,« .,*
il IL. ----- N Theee voluet predicted by N.S. Gill, R.S. Nyholm, and P. Pauling, Nature. 182. 168-70 (1958). I \ ' ' ' 1 * 1 1 3 k / • p. p. > 0 B.M. d tp 8 bonding \\ ^ ^ d2«, d,*_y* Squore planar t' t' . F re e ' Figure 1 12
the planar configuration (structure XV).* There is strong
e v i d e n c e , however, that the nickel compound is not
planar, but has a magnetic moment of 3.2 Bohr Magnetons,
indicating an octahedral structure
HO-fl
C XV
*For simplicity the carbon skeleton in these structures will be abbreviated to a line connecting donor groups, and the configuration ©bout the metal ion will be indicated by a symbolic structure. For instance, [Ni(DMG)2] (structure XIII) will be represented by
.o -n : ;n - o
K' Ni' \ \ ‘o -n: r-0''
and an octahedral species will be represented by the diagram X
with the six comers of the octahedron being occupied by the six donor groups, X. Finally, a third type of complex with dimethyl-
glyoxime exists; this type is found only in the nickel(il)
complex, [Ni(HDMG)2Cl2 ]> first prepared by Paneth and Thilo22 by passing dry hydrogen chloride over [Ni(DMG)2 ]. 20 Stoufer has shown that this compound may be prepared
from the reactants in alcohol containing hydrochloric
acid; this is a more general method applicable to many re
lated compounds. This compound, like [Ni(HDMG)Cl2 ], is
unstable in water losing hydrogen chloride to give the more
stable [Ni(DMG)2 ],
[Ni(HDMG)2Cl2] [Ni(DMG)2] + 2H* + 2C1~
[Ni(HDMG)2Cl2] has been shown1^ to have two unpaired
electrons. Consequently, one would expect it to be octa hedral (structure XVT) utilizing sp3d2 bonding. Since
Cl
:N-OH
Cl
XVI palladium(ll) and platinum(ll) seldom exhibit the octa hedral configuration, one would not expect such a species to exist with these metals. 14
In addition to the very characteristic complexes of HDMG, other oxime ligands, which are not quite so familiar, perhaps, form typical compounds. As mentioned above, the usual reaction of bidentate oximes with these metals produces a nonionic, water insoluble species of the type [MLg]. The other typical complexes are also p/r formed in some cases. Oxaldiamide dioxime (0xH2 ) forms an uncharged nickel(II) complex which may be converted in concentrated hydrochloric acid, to the octahedral form:
cone Ni(OxH)p*2HpO [Ni(0xHp)2 Cl2] HC1 ^
Likewise, the nickel(II) benzil dioxime (BH2 ) complex2^ will dissolve in hydrochloric acid to form a similar species; it is capable of dissociating ligand to give the type complex in which there is a one to one ligand to metal ratio and coordinated chloride:
[Ni(BH)2 ] + 2HC1 [Ni(BH2 )2Cl2]*-^ [Ni(BH2 )Cl2 ] + BH2
Also worthy of mention at this point are a number of nickel(il) complexes of the type (structure XVII) H H “ 0
XVII 15 prepared by Malatesta. 28 Most of these compounds are
paramagnetic with unusual magnetic moments of approxi mately 2,7 Bohr Magnetons, a value which is slightly low when compared with that for most spin-free nickel(II)
complexes. These compounds will be referred to later,
2. Complexes of 2,2»-Blpyridine.— 2,2’-Bipyridine
forms a number of different classes of complexes with nickel(ll), palladium(ll), and platinum(ll). Of these, only nickel(II) forms a complex containing three ligand molecules for each metal atom, [Ni(bipy)^]++ (structure XVIIl).2^ This complex is very stable and has been
XVIII resolved into optical isomers; one would expect it to have an octahedral configuration.
Nickel(ll), palladium(n), and platinum(ll) all form complexes with 2 , 2 '-bipyridine with a two to one ligand to metal ratio. The nickel(il) compound,
[Ni(bipy)2Cl2 3, which should be octahedral and isostructuraL with structure XVI, may be prepared in alcohol; on dis solution in water it immediately reverts to the more stable species, [Ni(bipy)g]'H ’. On the other hand, the palladium(II) and platinum(ll) complexes, [Pd(bipy)2 ]++ and [Pt(blpy)23++, may be prepared in water if an excess of bipy is present.3°*31 Livingstone^0 claimed that an equilibrium exists in such solutions:
[Pd(bipy)Cl2] + bipy [ Pd (bipy)2J++ + 2C1" and so, by adding the appropriate anion, [Pd(bipy)2]++ or [Pt(bipy)2]++, could be Isolated from aqueous solution.
The remaining class of bipy complexes is the one in which a one to one ratio of metal to ligand exists.
The species [Pd(bipy)Cl23 and [Pt(bipy)Cl2 ] are quite stable and were among the first compounds of bipy to be obtained with these metals.The corresponding [Ni(bipy)
(H20)2 3 S02j.*4h 20 was claimed to have been prepared by Jaeger and van Dijk,33 by evaporating an alcoholic so lution of [Nifbipy)^} SOij., containing excess nickel sulfate. No additional information appears to be available on this compound. The palladium and platinum compounds should, of course, be planar.
3. Complexes of Bidentate Amine Oximes.— M u r m a n , 3^*35 investigating the complexes of nickel(il), palladium(il), and platinum(ll) with 2-methyl-2-amino-3-butanone oxime
(AOH), has found four different classes of complexes. The complex bearing a unipositive charge and presumably con taining a hydrogen bridge, [M(A0)(A0H)3 (CIO^), is the 17 most stable species formed with nickel(ll). Palladium(ll) will also form this type of complex, but the platinum(il) compound has not been isolated. X-Ray diffraction data has been obtained^ for [Ni(AO) (AOH) ] (CIO^) and [Pd(AO)
(AOH)] (C102(.); the two crystals are isomorphic. Murmann claims the nickel complex, [Ni(AO)(AOH)] (CIO^), to be dia magnetic, which suggests a planar configuration.
The principal species for palladium(ll) and platinum(ll) is of the type [M(AOH)Clg]. Such a species has not been isolated with nickel(II). This species is analogous, of course, to [M(HDMG)Cl2] and [M(bipy)Cl23.
The complex type In which no ligand protons have been ionized, [M(AOH)2 3++, exists only with nickel(ll).
This species is thermodynamically unstable,* the kinetics are such, however, that It may be observed for a short time in acidic solution, before decomposing to nickel(il) and ligand.
An uncharged species, [M(AO)23, exists with nickel(il) in basic solution. This complex has not been isolated and the palladium(ll) and platinum(ll) analogs have not been reported. The failure of this typical oxime species to dominate the coordination chemistry of
AOH is very interesting and stands in contrast to the eG-dioximes discussed above. 18 As was pointed out at the beginning of this intro
ductory section, 2-pyridinaldoxime, the ligand presently
under investigation, bears certain distinct resemblances
to those ligand molecules which have been discussed.
These similarities should manifest themselves in the
different classes of complexes formed by 2-pyridinaldoxime.
In those cases where the ligand protons have not been ionized, the behavior should follow the pattern es
tablished by 2,2'-bipyridine. Dimethylgiyoxime and 2- methyl-2-amino-3-butanone oxime form complexes in which some or all of the oxime protons have been removed. These substances should have their analogs among the complexes of 2-pyridinaldoxime.
The studies reported here have involved the synthesis of a number of new complexes of nickel(il), palladium(ll), and platinum(ll) with 2-pyridinaldoxime.
In most cases the magnetic moments and molar conductivities have been determined. The infrared spectra have been recorded and some assignments have been made.
B. Experimental
1. Preparation of Ligand.
2-Pyridinaldoxime.— 2-Pyridinaldehyde obtained from Aldrich Chemical was dissolved in ethanol and reacted with hydroxylamine hydrochloride, maintaining the temper
ature between 0° and 30°C. by means of an ice bath. The
acid salt was neutralized with sodium hydroxide, and
water and dry ice were added to the solution. After
cooling for one hour, the mixture was filtered and the
yellow solid was recrystallized from water containing 10
per cent ethanol using decolorizing charcoal. The re
sulting white needles melt at 108°C.; sublimation begins
at a somewhat lower temperature. Literature value for the
melting point, 113.5°C. A sample of the oxime purchased from Aldrich Chemical Co. also melts at 108°C. Anal.
Calculated for CgHgNgO: C, 59,00; H, ^.95; N, 22.9^.
Pound: C, 58.95; H, 5.66; N, 22.82.
2. Nickel Compounds.
Tris-(2-pyridlnaldoxlme)-nickel(II) Iodide 2-
Hydrate.— Six and forty-two hundredths grams of nickel
chloride 6 -hydrate (0.027 mole ) was dissolved in 20 ml.
of water. Ten grams of 2-pyridinaldoxime (0.082 mole )
was added and the solution was stirred until all dissolved.
A solution containing 20 g. of potassium iodide in 20 ml.
of water was added and the resulting solution was warmed
to 50°C. At this temperature, any oil which had formed redissolved. After several minutes at 50°C., a tan solid precipitated and the mixture was allowed to cool to room temperature. After four hours the solid was separated by 20
filtration, washed with two small portions of water, and
dried in vacuo over P2O5 . Yield; 14.55 g. Anal. Calcu
lated for [Ni(C6H6N20)3 ]T2 *2H20: C, 30.23; H, 3.10;
N, 11.76. Pound; C, 30.17; H, 3.00; N, 11.93.
Diiodo-bis-(2-pyridinaldoxime)-nickel(II).— Pour
grams of nickel chloride 6-hydrate (0.017 mole ) was dis
solved in 10 ml. of water, and 4.00 g. of 2-pyridinaldoxime
(0.034 mole ) was added and dissolved. Five and seventy-
seven hundredths grams of sodium iodide was added to the
solution. The dark green solid was washed with one small portion of water and dried in vacuo over P20^. Yield:
8.29 g. Anal. Calculated for [Ni(CgHgN20 )2 I2 ]; C. 25.88;
H, 2.17; N, 10.06. Pound: C, 25.72; H, 2.35; N, 10.13.
Dichloro-bis-(2-pyridinaldoxime)-nickel(II).—
Sixteen and sixty-seven hundredths grams of nickel chloride 6 -hydrate (0.070 mole ) was dissolved in 350 ml. of boiling absolute ethanol. Seventeen and eleven hundredths grams of 2-pyridinaldoxime (0.140 mole ) was added; crystallization started immediately. The solution was boiled for 10 minutes and then allowed to stand over night. The green crystalline solid was removed by fil tration, washed twice with absolute ethanol, and dried in vacuo over P2O5 . Yield: 23.4 g. (89.7 per cent). Anal.
Calculated for [Ni(C6HgN20)2Cl2]: C, 38.55; H, 3.24; 21
N, 14.99; Cl, 18.97. Pound: C, 38.58, 38.56; H, 3.48,
3.41; N, 14.96, 14.74; Cl, 18.76.
Diacetato-bls-(2-pyridinaldoxime)-nickel(il).—
Sixteen and sixty-seven hundredths grams of nickel chloride
6-hydrate (0.070 mole ) was dissolved in 85 ml. of hot
water, and 17.11 g. of 2-pyridinaldoxime (0.140 mole ) was
added and dissolved. Twenty-one grams of potassium
acetate was added with stirring; the mixture was kept
on the hot water hath for 30 minutes and then allowed to
stand over night. The gray crystalline solid was removed
by filtration, washed with one portion of water, and
dried in vacuo over p2°5* Yield: 27.7 g. (94 per cent). Alternatively, this compound may be prepared
from nickel acetate 4-hydrate. Without added potassium
acetate, however, the yield is somewhat lower. Anal.
Calculated for [NifCgHgNgO^ (CHgCOOjg]: C, 45.64;
H, 4 .3 1 ; N, 1 3 .3 1 . Found: C, 45.31; H, 3.51; N, 13.32.
Acetato-aquo-bis-(2-pyridinaldoxime)-nickel(II).—
Twelve grams of diacetato-bis-(2-pyridinaldoxime)- nickel(il) (0.028 mole ) was mixed with 270 ml. of absolute ethanol and 30 ml. of water, heated on the water bath for twenty minutes, and filtered. This solution was poured into 1600 ml. of ether, filtered after two hours, washed with ether, and dried in the air. The tan solid was recrystallized by dissolving it in 90 per cent 22
ethanol, filtering, and pouring the solution into ether as
above. Anal. Calculated for [NI(CgHgNgO) (CgHc^O)
(CH3COO)(H2 0)J: C, 44.36; H, 4.26; N, 14.79. Found: C,
44.20; H, 4.55; N, 14.06.
Bis-(pyridine)-bis-(2-pyridinaldoxime)-nickel(II)
Monoiodide.— Five grams of dichloro-bis-(2-pyridinaldoxime)- nickel(il) (0.013 mole ) was dissolved in 15 ml. of warm
water and filtered; 2.50 g. of potassium iodide (0.015
mole ) was dissolved in 7 ml. of warm water and added.
Four and four-tenths ml. of pyridine (0.055 mole ) was
added with stirring to the above solution. After standing
one hour the orange crystalline solid was removed by fil
tration, washed three times with water, and dried in vacuo
over P2°5 78°C. Yield: 6.88 g, (90„3 per cent). Anal.
Calculated for [Ni(CgHgNgO) (CgH^NgO) (C ^ N j g 3 I: C, 45.01; H, 3.61; N, 14.32; I, 21.62. Found: C, 44.83, 44.65;
H, 3.73, 3.69; N, 14.01, 14.07; I, 21.93, 2 1 .5 8 , 21.97.
Bis-(2-pyridinaldoxime)-nlckel(II) Honoiodide.--
Bis-(pyridine)-bls-(2-pyridinaldoxime)-Nickel(II) mono
iodide was placed in a drying pistol over refluxing
benzyl alcohol (202°C«), allowed to stand at atmospheric
pressure for one hour, and then the pistol was evacuated.
After standing over P2 O5 AH vacuo at this temperature over night the sample consisted of dark brown crystals. Anal. Calculated for [Ni(CgHgNgO)(CgH^NgO)] I: C, 33.68; H, 2.59;
N, 13.10; I, 29.66. Pound: C, 33.58; H, 2.53; N, 12.93;
I, 30.03.
Bis-(pyridine)-bis-(2-pyridinaldoxime)-nickel(II).-- Ten grams of dichloro-bis-(2-pyridinaldoxime)-nickel(II)
(0.027 mole ) was mixed with 100 ml. of pyridine and heated to boiling with thorough stirring. Ten grams of
anhydrous potassium carbonate was added, the mixture was
again heated to boiling, 15-20 g. of sodium hydroxide
pellets was added, and the mixture was boiled with stirring
for 45 seconds. It was immediately filtered through a
large sintered glass funnel. The filtrate was cooled for
30 minutes, and the purple crystals were collected by
filtration, washed twice with pyridine, and dried in vacuo
over P205. Yield: 7.81 g, (63.6 per cent).
This solid contained some sodium chloride and
was recrystallized by dissolving in chloroform, filtering
to remove insoluble material', and pouring into a. volume
of pyridine equal to five times the volume of chloroform
used. The solution was allowed to stand in a stoppered flask over night before collecting the product by fil
tration and washing with pyridine. This recrystallization was performed twice. Yield on recrystallization: 77 per cent. Anal. Calculated for [Ni(CgH5N20)2(C^H^N)2]: C,
57.55; H, 4.39; N, 18.31; Cl, -. Pound: C, 57.22; H, 4.51; N, 18.86; Cl, 0.71. 24 Pyridine-bis-(2-pyridinaldoxime)-nickel(I I ).—
Five grams of dichloro-bis-(2-pyridinaldoxime)-nickel(II)
(0.013 mole ) was mixed with 30 ml. of pyridine and
boiled. Five grams of anhydrous potassium carbonate was
added and the solution was heated to boiling. Ten grams
of sodium hydroxide pellets was added, the mixture was
boiled for 45 seconds, and quickly filtered through a
large sintered glass funnel. The filtrate was immediately
placed on the hot plate and boiled for 15 minutes, then
filtered while hot. The resulting dark brown crystals
were washed with pyridine and dried in vacuo over P20^.
Yield: 2.4l g. (47.4 per cent). Anal. Calculated for
[Ni(C6H5N20)2 (C5H5N)]: C, 53.72; H, 4.51; N, 18.43;
Cl, -. Found: C, 53.86; H, 4.07; N, 18.09; Cl, 0.47.
Bis-(2-pyrldlnaldoxime)-nickel(II).— Bis-(pyri
dine) -bis- (2-pyridinaldoxime) -nickel (il) was placed in
a drying pistol at 100°C. in vacuo over P2C>5 for 16
hours. The drying pistol was opened in a dry box under
nitrogen. Before removing the sample from the dry box
the magnetic susceptibility tube was filled and capped,
and an ampoule for analysis was filled and protected with a magnesium perchlorate tube prior to sealing. The producted consisted of brown crystals. Anal. Calculated for [Ni(C6H5N20)2 ]: C, 47.89; H, 3.35; N, 18.62; Cl, -. 25 Found: C, 47.54, 47.29; H, 4.27, 4.10; N, 17.75, 17.64;
Cl, 0.73.
3. Palladium and Platinum Compounds.
Bis-(2-pyridinaldoxime)-palladium(II) Monochloride.—
Two grams of potassium tetrachloropalladite (0,0061 mole )
was dissolved in 70 ml. of water, 1.50 g. of 2 -pyridinal
doxime (0.012 mole ) was added, and the mixture was heated
to boiling, filtered and allowed to cool. The solid product
was removed by filtration and washed with water. This
material was quite impure, so it was recrystallized by dis
solving in 7 ml. of hot water, filtering, then adding three
drops of concentrated hydrochloric acid and allowing the
solution to cool. After standing over night the orange
crystals were removed by filtration, washed with water,
and dried in vacuo over P2 O5 . Yield: 1.51 g. (64.0 per
cent). Anal. Calculated for [Pd(CgHgN2 0)(CgH^N2 0)]C1:
c, 37.39; H, 2.88; N, 14.53; Cl, 9.20, Found: C, 37.38; H, 3.07; N, 14.31; Cl, 9.04.
Bis-(2-Pyridinaldoxime)-palladium(ll).— Three grams of potassium tetrachloropalladite (0.00916 mole ) was dissolved in 200 ml. of water, 2.24 g. of 2-pyridinal doxime was added (O.OI83 mole ). The solution was heated to boiling, digested until the solid dissolved, and then filtered. One gram of sodium hydroxide (0.025 mole ) 26 dissolved in 20 ml. of water was added to the hot filtrate
with stirring. When the addition was complete a mass of
yellow needles was present; the solution was allowed to
cool and filtered. The solid was washed with water and
dried in vacuo over P2°5* The solid was recrystallized by dissolving in
boiling chloroform (100 ml. of solvent per gram of
material), evaporating the solvent to half its original
volume, and cooling. The purified product was collected
by filtration, washed with chloroform, and dried in vacuo
over P2°5* Yield: 3.20 g. Anal. Calculated for [Pd
(C6H3N20)2 ]: C, 41.30; H, 2.89; N, 16.06; Pd, 30.58.
Found: C, 41.39; H, 3.00; N, 16.02; Pd, 30.52.
Bis-(2-pyrldlnaldoxlme)-platinum(ll).— Two grams of
potassium tetrachloroplatinite (0.00482 mole) was dissolved
in 90 ml. of hot water, and a solution of 1.18 grams of 2-
pyridinaldoxime (0.00966 mole) in 50 ml. of hot water was
. added. Within a few seconds, a fine, light colored solid
precipitated. Immediately, 0.4 grams of sodium hydroxide
(0.010 mole) in 20 ml. of water, was added. The precipi
tate dissolved leaving a clear brown solution; within
one minute, fine brown needles began to precipitate. The
solution was allowed to stand over night; the solid was
collected by filtration, washed with several portions of
water, and dried in vacuo over P203> Yield: 1.87 g. 27 This material was impure and was recrystallized
by dissolving in boiling chloroform (50 ml. per gram of
solid), filtering to remove a light tan solid, and
allowing the filtrate to stand over night. The brown needles were collected by filtration, washed with chloro
form, and dried in vacuo over Yield on recrystal
lization: 58.8 per cent. Anal. Calculated for [ Pt
(C6 H5N 20 )2]: C, 32.94; H, 2.30; N, 12.81. Pound: C,
3 2 .8 8 ; H, 3 .0 3 ; N, 1 2 .8 0 .
4. Physical Measurements.
Conductivity Measurements.— All conductivity measurements were made with a conductivity bridge, model
RC-16B, manufactured by Industrial Instruments, Inc.
Potentiometric Titrations.— Potentiometric titrations were carried out using a Beckman model G pH meter, with a saturated calomel electrode and a silver electrode. pH titrations were carried out using the same instrument with a saturated calomel electrode and a glass electrode.
Infrared Spectra.— Infrared spectra were obtained on a Perkin-Elmer model 21 recording spectrophotometer, with a sodium chloride prism. Band frequencies were corrected from standard polystyrene spectra. 28
Ultraviolet Spectra.— Ultraviolet spectra were
obtained on a Carey Model 10 recording spectrophotometer.
Job studies were conducted using a Beckman DU
spectrophotometer with quartz cells.
Magnetic Moments.— Magnetic moments were determined
using a Gouy type balance and solid samples; ferrous
ammonium sulfate 6 -hydrate and water were used as standards.
Temperature dependence studies of the magnetic
moment were conducted using the apparatus described by
Stoufer.2*"*
Analyses.— Analyses were performed by Galbraith
Microanalytical Laboratories, and also by Schwarzkopf
Microanalytical Laboratories.
C. Results and Discussion
1. Nickel(II) Complexes
Some rather interesting compounds have been pre
pared with nickel(il) and 2-pyridinaldoxime. Two distinct
types of compounds in which the ligand Is unionized have
been Isolated. They bear some resemblance to those com pounds of 2 ,2 '-bipyridine discussed in the Introduction.
The remaining compounds all have two properties in common.
All contain two moles of coordinated ligand and one or both ligand protons have been removed by ionization. For 29 simplicity of discussion these compounds have been divided into two classes, those in which only one ligand proton has been removed, and those in which both ligand protons have been removed. These complexes have been characterized by their magnetic moments, conductivities, and infrared spectra. They are discussed below in terms of their relationships to compounds that were previously known.
I\ stable complex, [Ni(HPOX)~]++, is readily pre cipitated from aqueous solution as the iodide salt. This is a tan, crystalline solid which has a magnetic moment of 3*12 Bohr Magnetons. In methanol the compound displays a molar conductivity of l8l.2 ohms-1, which approximates the values expected of a di-univalent electrolyte, 20 1 Stoufer has observed a range of 145-176 ohms- for di univalent electrolytes in this solvent. This compound appears to have the octahedral configuration and to be completely similar to [Ni(bipy)^]++. Dichloro-bis-(2-pyridinaldoxime)-nickel(II),
[Ni(HP0X)2 Cl2 ] is precipitated from a solution of nickel chloride 6-hydrate In ethanol by the addition of 2-pyri- dinaldoxime. This complex consists of fine, green crystals. It has a magnetic moment of 3*16 Bohr Magnetons, and shows a molar conductivity In methanol of 111.4 ohms-1. 20 Stoufer has observed similar values of the conductivity 30 TABLE 2
MAGNETIC MOMENTS AND CONDUCTIVITIES OP COMPLEXES OP 2-PYRIDINALDOXIME
^ e f f -%(in MeOH) Compound (B.M.) (it-1 at 25°C.)
Ni(HP0X)3I2 #2H20 3.12 181.2
Ni(HP0X)2Cl2 3.16 111.4
Ni(HP0X)2Ae2 3.12 33.9 Ni(POX)(HPOX)(Ac)(H20) 3.08 32.0
Ni(p o x )(h p o x )(py)2i 3.18 89.7 Ni(POX)(HPOX)l 3.01 ' 88.8
Ni(P0X)2 (py)2 2.83 13.4
Ni(P0X)2 3.56* - - 2.74*
Pd(POX)(HPOX)Cl - - 86.5
Pd (POX) 2 - - 2.6
Pt(P0X)2 - - 3.7
*Solid sample. Moment calculated using the ex perimentally determined Weiss constant, 0, with a value of 226.3°. ^Solution in chloroform. Moment calculated assuming 0=0.
for closely related substances, and has postulated that some of the chlorides, which were originally coordinated, have undergone solvolysls, according to the equations 31 [Ni(HP0X)2 Cl2 ] + CH3OH * [Ni(HPOX)2 (CH3 OH)Cl]+ + Cl“
and
tNi(HP0X)2 (CH3 0H)Cl]+ + CH3OH --- > [Ni(HP0X)2 (CH3 0H)2]++ + CL
with the second step being less extensive than the first.
[Ni(HP0X)2 Cl2 ] appears to bear the octahedral con figuration. In its physical properties, method of prepa
ration, and probable configuration, it bears a very close
resemblance to [Ni(bipy)2Cl23 and [Ni(HDMG)2 Cl2 3 . However, there is a principle point of contrast. When [Ni(HPOXjgC^j
is dissolved in water, the solution retains its green
color; there is no apparent reaction. In fact, [Ni(HP0X)2
(0^ 3 0 2 )2 ] an<3 [Ni(HP0X)2 l2 ] may be prepared in aqueous solution. These observations are distinctly contrary to
what is observed when [Ni(blpy)2 C12] and [Ni(HDMG)2 C12 ]
are mixed with water, the former immediately reverting to
[Ni(bipy)3 ]++ and the latter to [Ni(DMG)2]. The next class of complexes may be considered to
be derived from the compound just discussed, [Ni(HP0X)2 Cl2], by the removal of one ligand proton and the replacement or
removal of the coordinated chlorides. The compounds of this type which have been prepared are [Ni(POX)(HPOX)
(C2H3 O2 )(HgO)], [Ni(POX)(HPOX)(py)2 ]I, and [Ni(POX)(HPOX)]I. It can immediately be seen that these compounds are analo gous to [Ni(AO)(AOH)]+ In their distribution of ligand protons. 32 The monoacetate, [Ni(POX)(HPOX)(CgH^C^)(H20)], was
the first compound of this class to be prepared. The gray
diacetate, [Ni(HP0X)2Ac2], dissolves in water or alcohol
to give a brown solution. The addition of ether causes
the tan monoacetate to be precipitated:
[Ni(HP0X)2Ac2] + H20 »[Ni(POX)(HPOX)(Ac)(H20)] + HAc
This compound has a magnetic moment of 3«°8 Bohr magnetons, and there is little doubt of its showing an
octahedral configuration. The molar conductivity in
methanol for [Ni(POX)(HPOX)(C2H302 )(H20 )] is 32.0 ohms’1, which indicates that this compound does not undergo ex
tensive solvolysis.
The second compound of this class, [Ni(POX)(HPOX) (py)2]Ij is precipitated as orange crystals from an aqueous solution of [Ni(HP0X)2C12] and potassium iodide by
the addition of three equivalents of pyridine. One
equivalent of pyridine is apparently utilized in the
neutralization of an oxime proton, since precipitation
does not start until after the first equivalent has been
added. The other two equivalents of pyridine coordinate
to the nickel(il) atom. The resulting conclusion, that
the nickel(il) is octahedrally coordinated, is substanti
ated by the observed magnetic moment of 3.18 Bohr Mag
netons. This compound displays a molar conductivity (in methanol) of 89.7 ohms’1. It is felt that this value for 33 the conductivity may well serve as a standard for complexes which are uni-univalent electrolytes in methanol. The value for sodium chloride in this solvent is 96.9 ohms”'*’ at 10“3 molar.3?
The last compound of this class, [Ni(POX)(HPOX)]I,
is prepared as brown crystals by removal of pyridine from
[Ni(POX)(HPOX)(py)2]I at 200°C. in vacuo. In methanol
fNi(POX)(HPOX)]I is a uni-univalent electrolyte, with a molar conductivity of 88.8 ohms”-*-, a value almost identi cal to that obtained for [Ni(POX)(HPOX)(py)2]I. [Ni(POX) (HPOX)]I is the most interesting compound of these three, in that it too is paramagnetic (with a magnetic moment of
3.01 Bohr Magnetons). One would expect, from the observed stoichiometry, that this substance would be planar and, consequently, diamagnetic, since the magnetic suscepti bility of the similar compound, (Ni(AO) (AOH) 3 (ClOij.), indicates a square planar configuration.3^ There are two possible explanations for the apparent coordination number of six. According to the first, although the iodides are ionic in solution, they might well be coordinated in the solid and shared between nickel atoms. Such a sharing of iodide ions between molecules would produce chains of octahedra linked at comers. The other possibility re quires that the oxime oxygens act as donors. Again the octahedra would not be discrete but linked in one of several possible ways (structure XIX). In view of the
XIX behavior observed among the uncharged complexes (below), this latter suggestion seems more probable.
During the study of [Ni(POX)(HPOX)]I, a rather unusual behavior was observed. Dilute aqueous silver nitrate did not precipitate silver iodide from this
compound. Subsequent addition of sodium chloride to the
silver nitrate-complex solutions (with excess complex present) caused no precipitation of silver. Silver iodide was liberated on the addition of nitric acid, but since
the complex is destroyed at low pH, this only served to show the presence of iodide.
A potentiometric titration with silver nitrate, using a silver electrode, showed a sharp break in potential at one equivalent. Job’s method of continuous variations^
(Figure 2) corroborated the 1:1 interaction.
This behavior can be rationalized by assuming that either a "super-complex" is formed, i.e., silver ion is E xtinction 0.200 0.400 0.300 0.500 QIOO o Mto o Cniuu Variations Continuous of Method Job ocnrtos I" molar I0"4 Concentrations, t 1 m|t 416 at AqNOs and [Ni(P0X)(HP0X)]l I. of [Ni(P0X)(HP0X)]l [Ni(P0X)(HP0X)]l of I. l o AqNO, of ml. Figure 2 Figure 35 36 bound to the complex molecule (structure XX), or colloidal
H
XX
silver iodide is formed. If the latter alternative is
realized, the colloid should be removed in the ultra
centrifuge. In Figure 3 are shown three ultraviolet ab
sorption spectra; the first curve is the monoiodide complex,
the second curve is the monoiodide complex and silver ion
(three hours after mixing), and the third curve is the
complex and silver ion after centrifugation for three hours (40,000 r.p.m.). These spectra appear to prove
conclusively that the interaction does indeed Involve colloid formation. Further, since the complex is not re moved from solution (there is still absorption of light), the colloid is silver iodide, not a silver-complex deriva tive. These observations are quite interesting because in dilute solution there is very little scattering of visible light, indicating that the colloid is of low molecular weight.
The class of complexes which remains to be dis cussed is that which is derived from [Ni(HP0X)2C123 by 100 % Tronsmission 0 5 210 lrvoe Asrto Setu o N(O)H Sltos n Ter neato wt Sle Ion Silver with Interaction Their and Solutions Ni(POX)jHl of Spectrum Absorption Ultraviolet 250 — . 267 x IO"9 M. in Ni (POXfeHI Ni in M. IO"9 x 267 . — HI (POX)2 Ni in M IO's x 67 2 —— ae egh mu Length, Wave iue 3 Figure 7 I‘s i NitPOXfcHl in M IO‘ s x 67 2 n 32 x 05 . n AgN03 in M. I0"5 x 3.29 ond n 32 x T M i AgN03 in M. XT5 x 3.29 and fe ultracentrifuge after 350 0 0 3
37 360 the removal of two oxime protons from the ligand and the removal or replacement of the chlorides to give an un charged compound of the type [NifPOXjgl. Prom the be havior of similar ligands (as discussed in the introductory section) it would seem likely that a diamagnetic, square planar species should precipitate from water. From obser vations on similar species one might even expect this material to be red or orange. Such a compound is not readily obtained by the reaction of nickel(il) salts with
2-pyridinaldoxime. The second oxime proton is relatively difficult to remove. As mentioned above, aqueous pyri dine suffices to remove the first proton. In water, the second proton may be removed in a highly concentrated caustic solution. This treatment causes an oil to precipi tate. An alternative procedure involves the removal of chloride from [NifHPOX^Clg] with an anion exchange resin in the hydroxide cycle. To isolate the product of this treatment, the solution must be evaporated to dryness.
The products of these reactions do not analyze well; in addition to the carbon-nitrogen ratios being nonideal, there appear to be several moles of water present which cannot be removed by storing over P2°5* These samples are strongly paramagnetic.
Finally, it was necessary to abandon water as a solvent and employ anhydrous pyridine. By reacting a 39 pyridine solution of [Ni(HP0X)2 Cl2 ] with solid sodium hydroxide an uncharged complex, [Ni(P0X)2 (py)2 ], was obtained. This compound forms as gleaming, purple crystals. Its conductivity in methanol (13.4 ohms”*) verifies its nonionic nature, and the magnetic moment of the solid (2.83 Bohr Magnetons) substantiates the proposal of an octahedral configuration, which one would suspect in view of the presence of six donor groups.
Compounds of the general formula [NiL2 py2 ] in volving bidentate, uninegative ligands are well known.
These compounds will liberate the pyridine under varying conditions yielding the planar compound
[NiL2py2 ] --- > [NiL2 ] + 2py
Stratton-^ has observed the separation of dipyridine-bis-
(salicylalhydrazone)-nickel(II) from pyridine as large, red crystals. On drying, however, these crystals rapidly lose pyridine and crumble to a light brown powder. On the other hand, he has observed that dipyridine-bis-(salicylal- phenylhydrazone)-nickel(il) is quite stable. His obser vation that the former compound, dipyridine-bis-(salieylal- hydrazone)-nickel(il), on loss of pyridine, yields a para magnetic material is most interesting. His explanation is cited below. 40
The nickel(II) complex of 2-pyridinaldoxime,
[Ni(P0X)2 (py)2], retains its pyridine tenaciously and may
be dried in vacuo over P20^ without any apparent loss in weight. In order to effect removal of the pyridine the
temperature must be raised to approximately 100°C.
It is interesting to observe that a compound
containing a single pyridine, [Ni(P0X)2py], forms under
conditions intermediate to those for the preparation of
[Ni(P0X)2 (py)2 ] and for the removal of the pyridine.
[NifPOXjgPy] is formed in pyridine solution but at a
temperature where pyridine is lost by the solid compound,
[Ni(P0X)2 (py)2 ],
Bis-(2-pyridinaldoxime)-nickel(il), [Ni(P0X)2 ], is prepared by heating the dipyridinate, [Ni(P0X)2 (py)2], in vacuo at 100°C. This material is not only unusual with respect to the method required for synthesis, but also in a number of other respects. Of all the compounds of nickel(II) with 2-pyrldinaldoxime this compound,
[Ni(P0X)g], has the greatest likelihood of showing the planar configuration. [Ni(P0X)g] is, however, para magnetic with a magnetic moment which appears to have the value of 2.6 Bohr Magnetons (calculated using the equation
(1) -Veff = 2.83 V"XA T This value is too low for two unpaired electrons (theoreti cal, 2.83 B.M. with no orbital contribution). There are two possible explanations for this low
observed moment. The Curie-Weiss law
1 T © + Q Q
(where is atomic susceptibility, T is the absolute
temperature, and Q and © are constants) contains a cor rection factor, 0. If © is negligible, the magnetic moment may be calculated by use of equation (1) above.
If © is not negligible, one must use the equation
(3) ^ e f f = 2 -83 V % (T+6) for the calculation of the magnetic moment.
A second explanation for this low observed moment is -that there is an equilibrium between two electronic spin states, spin-paired and spin-free in this case. 20 Stoufer' has discussed this possibility for some cobalt(II) complexes which exhibited unusual magnetic moments. If such a situation exists, the Curie-Weiss law would not be obeyed, and a curve instead of a straight line would result in a plot of i/XA vs. T.
In Figure 4 such a plot has been constructed for
[NifPOXjg]# The magnetic susceptibility is seen to follow a Curie-Weiss dependence on temperature; consequently, the second explanation (that of spin state equilibria) need be considered no further. 42
Tamptrotura Dtpandanct of Moanatic Suscaptibility of [Ni(POX)j]
400 i « si opt • 0.6331
£ ■ inttrcapt « 143.3 O' 226.3
350-
Ni
300
Curva odjuafad to data by laast tquarts troatmant
250-
200 250 300 400 T (*K)
Figure 4 43 g in Figure 4 are given the values of Q, --- , and Q. 0, as determined by a least squares treatment of the data.
© is found not to be Insignificant, but to have the value
of 226.3°• Using this value for 0 in the calculation of
the magnetic moment, a value of 3*56 Bohr Magnetons (with
a standard deviation of t 0.02 B.M.) is obtained.
The uncharged complex [Ni(P0X)2 ], is apparently nonplanar. Since this material was never exposed to moisture but was handled only in a dry box, it is con
cluded that the substance does not exist as a hydrated
species such as [NifPOXjgCHgO^]. Consequently, a struc
ture must be proposed similar to the one suggested for
[Ni(POX)(HPOX)]I (structure XIX), In which the oxime oxygens are required to act as donors. This is similar to the structure proposed by Stratton39 for paramagnetic bis-(sallcylalhydrazone)-nickel(II) in which uncoordinated hydrazone NH2 groups are assumed to act as donors to nickel atoms of adjacent molecules, resulting in an octa hedral configuration. oft At this point Malatesta'sc compounds might tvell be mentioned again. This worker prepared several oxime 44 and isonitroso complexes with nickel(ll) which appear to be of the type (NiL2 3. Most of these compounds have magnetic moments near 2.7 Bohr Magnetons, and only a few of them are diamagnetic. It would be of great interest to study the temperature dependence of the magnetic susceptibility of these compounds, in view of their low magnetic moments.
Another structure which must be considered for
[Ni(P0X)2 J is the tetrahedral configuration. Although o this configuration is not favored for a d ion in terms of the crystal field theory, it apparently exists in some cases.2*'0 Gill, Nyholm, and P. Pauling2*'0 point out that tetrahedral nickel(ll) should have a magnetic moment near
3.8 Bohr Magnetons. The calculated value of 3.56 for
[Ni(POX)23 is not too far removed from this value, and this configuration remains a possibility. Also, dis solved in a noncoordinating solvent (chloroform) this compound is still strongly paramagnetic ( ^ eff = 2.74 B.M., assuming 0=0). This observation also suggests the tetrahedral structure; however, it should be noted that this value is substantially lower than that expected for such a configuration.
2. Palladium(ll) and Platinumfll) Complexes
Palladium(ll) and platinum(ll) behave exactly as one might expect in their coordination with 2 -pyridinaldoXLme. 45 They readily precipitate the complexes of the stoichiometry, [M^-T(POX)2], from aqueous solutions contain ing two equivalents of base, in sharp contrast to the nickel(ll) complexes with this ligand.
The bis-(2-pyridinaldoxime)-palladium(ll) complex is a strong, dibasic acid. The titration of a mixture containing two moles of ligand and one mole of palladium(n) with sodium hydroxide proceeds to a sharp break in pH at two equivalents of base (Figure 5). There is no perceptible inflection in the curve at one equivalent of base. The shape of the curve is typical of a strong acid-strong base titration.
From this data one would suspect that other palladium(ll) complexes could not be isolated. By adding concentrated hydrochloric acid to a solution of ligand and palladium(ll), however, a monoprotonated species, [Pd(POX)
(HPOX)]C1, crystallizes. This material undoubtedly precipi tates because of a favorable lattice energy; this is an excellent example of the fact that dominant species exist ing in solution are not always those which are isolated as solids from the same solutions.
When this compound is dissolved in methanol it exhibits the conductivity of a uni-univalent electrolyte
(86.5 ohms-1). Although the ion [Pd(HP0X)2]++ is a strong dibasic acid in water, the species in methanol 10.0 System Pd** - HPOX, titrated with NaOH One mole Kt PdCI, two moles HPOX, in water 7 w lrt-1 molar in palladium
8.0
Two equiv. of base 6.0
4.0 Calc'd. one equiv. of base
^0
20 25 30 35 40 ml. NaOH
-tr Figure 5 0\ 47 might be [Pd(POX)(HPOX)]+Cl". Ionization of the ligand proton according to the equation
[Pd(POX) (HPOX)]Cl [Pd(P0X)2 ] + H+ + Cl" might be expected to give rise to a much higher value of the conductivity because of the high conductance of the hydrogen ion.
The only platinum(ll) complex which has been isolated in pure form is the uncharged complex, [Pt(P0X)2 ].
Attempts to prepare other species have resulted only in mixtures. The pH of the solution must be raised to the neutral point in this preparation by the addition of base in order to obtain a reasonably pure product.
On recrystallization of the platinum(ll) compound a light tan material, insoluble in chloroform is separated from the major product. This material gives an analysis which suggests it to be the mono-(2 -pyridinaldoxime) complex salt, Na[Pt(P0X)Cl2 ]. This is not surprising considering the tendency of palladium and platinum to form such species; i.e., [Pt(bipy)Clg]. A similar palladium(ll) complex has been obtained, but under somewhat different conditions (see Section H, this dissertation).
D. Discussion of Infrared Spectra
The infrared spectra of the compounds studied in this work have been recorded. The spectra of those compounds which have not previously been reported in the literature are recorded in Figures 6 to 18, and summarized in Tables 3 to 6, together with several band assignments.
Infrared spectroscopy was found to be a very convenient control technique in the study of the reactions of co ordination compounds (Section II of this dissertation).
While attempts were made to obtain pure reaction products, this goal was not always realized and the infrared ab sorption spectrum, in many cases, served to verify the nature of an impure substance. The infrared spectra have been valuable in a consideration of the structures of the complexes prepared. When protons are removed from co ordinated 2-pyridinaldoxime, there are significant changes in the infrared absorption spectra. These are discussed below.
Detailed studies of the infrared absorption spectra of coordination compounds similar to those under consideration in this dissertation have been reported, if-1 Figgins has studied 2-pyridinal methylimine, 2,6-pyridin- dial-bis-methylimine, biacetyl-bis-methylimine, and their iron(ll), cobalt(ll) and nickel(ll) complexes, while PO Stoufer has studied biacetyldihydrazone, 2-pyridinal- hydrazone, 2,6-pyridindialdihydrazone, 2-pyridinal-p- tolylimine, and their complexes with the same series of metals. Extensive use has been made of the work by the above mentioned authors. TABLE 3
INFRARED ABSORPTION SPECTRA AND ASSIGNMENTS FOR COMPLEXES OF 2-PYRIDINALDOXIME Complexes Containing Unionized Ligand Frequencies In cm”1
Assignment HPOX n i (h p o x )3I2 n i (h p o x )2 r2 n i (h p o x )2c i 2 n i (h p o x )2a c 2 42H20
HoO 3410 sh 3417 m 3406 vw 3424 m 3300 sh 3299 sh-b 3230 sh 3194 s- 3183 s 3160 s 3104 sh
Ring C-H 3070 s 3060 s-b 3082 s 3084 sh" — 3015 s 3003 s-sp 3003 m 3007 w C-H 2880 b_ 2932 sh (side 2791 s 2779 vw chain) sh 2768 w 2767 : it o o 1760 m-b
C»N 1625 w 1633 w-sh 1642 m-sp 1654 m-sp 1644 m (hcycllc^ 1614 sh 1632 sh _
Band I 1600 s-sp 1599 s-sp 1608 s-sp 1611 s-sp 1613 s
Band II 1569 s-sp 1563 w 1571 W 1574 w 1576 sh
1545 S h 1559 sh 1550 s TABLE 3 (Contd.)
Assignment HPOX Ni(HPOX)3I2 Ni(HPOX)2I Ni(HP0X)2Cl2 NifHPOXjgACg • 2H20
-N=0 1520 s
Band III 1477 s-sp 1478 s-sp 1489 s-sp 1490 s-sp 1481 m 1466 m-sp 1480 sh
Band IV 1439 s-sp 1443 m 1431 w 1438 vw 1440 sh 1410 s-b 1386 vw 1383 m 1388 vw
1343 sh~l 1327 s 1334 w J 1318 s 1318 s 1298 m 1292 sh] 1307 s 1307 s 1279 s ] ] 1267 w .J 1259 m-sp 1257 m 1254 w 1252 si 1247 m-b 1231 s 1239 sj 1218 w 1216 shh l 1215 m 1217 m 1214 m-sp|
=N-0(?) 1159 s-sp 1158 m 1158 m 1158 m 1163 m 1152 m 1111 w TABLE 3 (Contd.)
Assignment HPOX Ni(HPOX)qlo Ni(HPOX)?Ip Ni(HP0X)pClo Ni(HP0X)pAco •2H20 ^ ^ ^
1103 s-sp 1108 w-b 1104 1070 sh 1087 w 1087 vw 1056 w 1055 vs 1069 1046 w 1049 s IO36 vs 1022 sh 1020 w 1018 w 1015 1005 w 1011 vw 996 sh 985 s 979 s _ 962 m
946 s 956 w-b 940 m- b 946 w~ 937 m_. 921 w 925 916 899 sh ’] 0 0 0 0 3 C-H bend 892 m 891 m -'j 886 m 888 1 00 879 s C-H rock 778 s 775 s-b 779 s 776 s_ 776 771 s 774 sh '] VJ1 TABLE 3 (Contd.) Assignment HPOX Ni(HP0X)^I2 Ni(HP0X)2I2 Ni(HP0X)2Cl2 Ni(HP0X)2A c 2 •2H20 756 fa 753 sh| 754 m 751 $ 741 s 746 w-b 751 mj C-H bend 668 s 676 m 673 m 673 s 681 s 670 m 659 s s = strong, m = medium,, w = weak, b = broad, sh s shoulder, sp = sharp, v = very. v_n ro X TRANSMISSION % TRANSMISSION 100 100 BO 0 6 20 40 60 - 0 8 20 0 — 0 0 0 3 0 0 0 4 0 0 0 3 0 0 0 4 L J 2000 2000 nrrd bopin pcrm f N(PXj I [Ni(HPOX)j] of Spectrum Absorption Infrared nrrd bopin pcrm f (HPOX) of Spectrum Absorption Infrared 50 00 0 0 9 1000 1500 O 700 BOO ill I RQEC (m'1) (cm FREQUENCY RQEC (cm."1) FREQUENCY _____ I ______1000 2 ■ 2HgO L 900 800 TOO 00 U1 X TRANSMISSION * TRANSMISSION 100 100 60 0 4 0 6 40^ 80 20 0 8 20h . 3000 0 0 0 4 3000 0 0 0 4 nrrd bopin Spectrum Absorption Infrored 2000 2000 nr a Asrto Setu o [iHO) z] Iz [Ni(HPOX)z of Spectrum Absorption Infra rad 1500 1500 RQEC ( *1) m (c FREQUENCY RQEC (m.'1) (cm FREQUENCY 1000 OOO 900 00700 0 80 0 0 8 700 % TRANSMISSION % TRANSMISSION 100 0 6 0 4 0 6 00 0 2 20 0 4 80 - 3000 0 0 0 4 d00 3000 0 0 4d -I ______L 2000 2000 _ 1 J_J nrrd bopin pcrm f N HPOXljICHjCOO^] ( [Ni of Spectrum Absorption Infrored -- Infrared Absorption Spectrum of of Spectrum Absorption Infrared 1 __ I ___ 50800 1500 1500 I ___ RQEC (cm.-1) FREQUENCY I ____ RQEC (m.' (cm FREQUENCY I _____ 1_ [NHPOX)(HPOX)(CH 1000 00 900 1000 j COOKH£»3 00 9 800 700 U1 VJI TABLE 4 INFRARED ABSORPTION BANDS AND ASSIGNMENTS FOR COMPLEXES OF 2-FYRIDINALD0XIME Complexes Having One Ligand Proton Ionized Frequencies in cm**1 Assignment [Ni(POX)(HPOX) [NI(POX)(HPOX) [Ni(POX) [Pd(POX) (Ac)(H20 )] (py)2H (HPOX)]I (HPOX)]Cl 3465 sh - H20 3395 s-1S> 3409 m 3363 s 3408 s C-H Stretch 3025 m 3050 sh-b 3085 m 2977 m C=0 1772 m-vb C=N 1637 w 1630 sh 1626 sh “ 1630 sh (acycllq) 1610 m Band I 1607 m 1606 s-sp 1608 s-sp 1594 m Band la 1585 sh Band II 1568 sh 1553 sh 1588 sh 1580 m — 1556 s = 1547 m 1544 m 1547 s h ” 1546 sh 1535 sh 1529 sh 1527 sh 1526 m 1526 sh -N=0 1515 sh 1522 sh 1 5 H sh 1510 sh 1510 sh TABLE 4 (Contd.) Assignment [Ni(POX)(HPOX) [Ni(POX)(HPOX) [Ni(POX) [Pd(POX) (Ac)(H20)] (py)2 3i (HPOX)]I (HPOX)]Cl Band Ilia 1489 sh Band III 1480 m 1478 s-sp 1477 s-sp 1479 s-sp 1460 sh _ Band IV 1428 sh~ 1442 s-sp 1435 w 1425 w-b Band IVa l4l8 sh _ 1397 s-b 1340 m 1337 w 1348 s-sp 1333 m " 1303 m 1300 m 1303 m 1256 sh 1253 m 1246 sh “ 1242 sh 1233 s-sp 1221 w 1215 m 1216 m 1206 w =N-0? 1157 m 1167 shf 1150 w 1151 w 1150 sj 1128 shl 1118 m 1118 w j 1114 m-sp 1093 m 1090 m-b 1074 m TABLE 4 (Contd.) Assignment [Ni(POX)(HPOX) [Ni(POX)(HPOX) [Ni(POX) [Pd(POX) (Ac)(H20)] (py)2 ]I (HPOX)]I (HPOX)]Cl 1065 m “ 1051 s-b 1056 sh 1043 s 1041 m 1021 w-b 1015 m 1023 sh 1024 m 920 w 953 m 915 m-b C-H bend 885 m-b 906 m-b 886 w 895 m-b C-H rock 777 s-b 775 m 775 s 765 s 756 m ~ 753 vw 75^ m 750 m _ 749 m 69^ sh" 700 m 714 m-b C-H bend 681 m-t 683 m 678 m 665 sh~| 662 m 660 w-b 669 w 659 m s = strong, m = medium, w = weak, b = broad, sh = shoulder, sp = sharp, v = very. ui CO % % TRANSMISSION % TRANSMISSION 100 100 0 8 - 0 6 - 0 4 0 2 - 0 6 0 2 40- - r - - 3000 0 0 0 4 00 000 0 30 4000 i u _i ~2ofeo 2000 j i l i l i i i i — Infrared Absorption Spectrum of [NilPOXKHPOXKpyJj] I [NilPOXKHPOXKpyJj] of Spectrum Absorption Infrared nrrd bopin pcrm f [Ni(POX)(HPOX>]I of Spectrum Absorption Infrared - l I 1 l 1 50 R 1500 50 00 900 1000 1500 RQEC (cm.'1) FREQUENCY RQEC (cm." FREQUENCY ___ l ___ l ____ J 3 L J o goer bo _ _ l _ 0 0 8 800 J J ______L I______L -T&r 700 VJ1 VO X TRANSMISSION lOOr 20 40 60 80 1 i i 01 4000 3000 2000 I L I L I I J 1500 I L I J nrrd bopin etu f P(OX)HP )]CI X PO )(H X [Pd(PO of pectrum S Absorption Infrared RQEC (m.'1) (cm FREQUENCY 1000 1 I I I I 1 J 900 800 700 a\ o TABLE 5 INFRARED ABSORPTION SPECTRA AND ASSIGNMENTS FOR COMPLEXES OF 2-PYRIDINALDOXIME Uncharged Complexes Frequencies in cm"! Assignment [Ni(POX)2 (py)2] [Ni(P0X)2py] [n i (p o x )2 ] [ Pd (P OX) 2 ] [Pt(p o x )2 h 2 o 3306 s-b 3400 s 3353 s-b 3320 sh ~ 3361 s-b 3177 s-b C-H Stretch 3038 m 3019 sh 3030 sh C-H 2943 s (Side chain) C=N 1647 vw 1633 w 1634 s h 1659 w 1661 sh ~ (acyclic) 1634 vw Band I 1598 s-sp 1603 s-sp 1608 s-sp 1605 s-sp 1616 s-sp 1599 S h — Band la 1582 sh 1589 sh 1583 sh Band II 1560 sh 1568 w 1583 sh 1561 vw 1564 vw 1544 sh 1546 sh 1549 sh 1528 sh 1 — -N=0 1515 m 1519 mb 1513 sh 1515 sh 1500 m 1504 sh 1505 s 1505 m TABLE 5 (Contd.) Assignment [Ni(POX)2 (py)2l [Ni(P0X)2py] [Ni(P0X)2 ] [ Pd (P OX) 2 ] [Pt(P0X)2 ] Band Ilia 1489 sh" 1484 sh ~ Band III 1469 s 1476 s-sp 1478 s-spf 1482 s~| 1491 s i 1460 sh_ 1466 sh 1464 sh J 1463 sh) 1465 sh) Band IV 1438 m 1449 m-sp 1436 w 1424 m 1433 s Band TVa 1415 m 1422 m 1348 sh 1345 sh 1340 m 1344 s 1348 s 1328 s-sp 1343 m-sp 1333 m-sp 1315 sh 1308 w 1308 w “ 1304 w 1254 w 1256 w 1255 s 1247 w 1240 w 1246 s 1233 m 1 1224 vw 1227 m 1217 m _ 1191 w 1175 s 1182 -N-0(?) 1158 w 1165 sh 1157 1159 s 1154 sh ~ 1150 m ~ 0 1136 s-b 1145 s = 1131 sh 1136 sh 1120 s 1118 1100 sh 1100 m “ 1108 sh TABLE 5 (Contd.) Assignment [Ni(POX) 2 (py)2 ] [Ni(PQX)2 py] [Hi(PQX)2 ] [Pd(P0X)2 ] [Pt(poxy 1070 wl 1070 nff 1094 1059 wj 1065 sh] 1057 vw 1054 w 4 ) 1038 nT 1040 m 1039 w 1029 mj 1015 w 1019 w 1029 w 1009 m 990 m 987 w 980 m 959 in-b C-H bend 893 m” 896 m 890 m-b 892 m 907 w-b 879 m 881 m 838 s 832 m 833 m 828 m-b 791 m 805 w-b C-H rock 769 s 777 m 775 s 775 s 768 m-b 753 sh 754 m 747 s_ 749 m 706 vs 707 s C-H bend 675 m~ j 677 s“ ] 680 m-b 678 m 679 m 668 m_ 668 sh] 668 vw 664 m 658 w-b s = strong, m = medium, w - weak, b = broad, sh = shoulder, sp = sharp, v = very. 0? h* *=d c (D 85 t- E < z CO i % TRANSMISSION 100 0 8 0 4 100 60 20 0 8 0 6 20 0 4 00 3000 4000 2000 1 I L I I I 1 J nrrd bopin pcrm f [NKPOXljIpylz]' of Spectrum Absorption Infrared nrrd bopin pcrm f [NitPOXljIpy)] of Spectrum Absorption Infrared 5010 900 0 9 1000 1500 50TOO 1500 RQEC fm'1 fcm FREQUENCY RQEC ( .'1) m (c FREQUENCY J _ _ _ _ _ U TOGO' J ______700 0 0 8 ______I _ _ _ _ I______L. a\ -!=■ % % TRANSMISSION 100 % TRANSMISSION 100 0 6 - 0 8 20 - 0 4 0 8 - 0 6 - 0 4 0 2 - - 00 3000 4000 0 0 0 3 0 0 0 4 J ______1_ nrrd bopin pcrm f [NilPOXlj]0 of Spectrum Absorption Infrared 000 2 2000 J I LJ L I I I -J nrrd bopin pcrm f [Pd(POX)J0 of Spectrum Absorption Infrared 1500 50 00 900 1000 1500 RQEC (m.'1) (cm FREQUENCY RQEC 1m'1) 1cm FREQUENCY ____ _ L 00 900 1000 _L X Soo~ o o “S 0 0 8 700 700 VJ1 X X TRANSMISSION 100 80 20 0 4 0 6 - - 4000 3000 nfae bopin etu f [Pt(P0X)2]' of pectrum S Absorption frared In 1500 RQEC (cm.-1) FREQUENCY Figure 13 Figure 1000 900 800 700 on TABLE 6 INFRARED ABSORPTION SPECTRA AND ASSIGNMENTS FOR COMPLEXES OF 2-FYRIDINALDOXIME Reaction Products Frequencies in cm-1 Assignment [Pt(P0X)2 [Pd(P0X)2 [Pd(POX)2 [Pd(POX) [Pd(POX-COCH3) [Pt(P0X-C0CH3)2]Cl2 Br2] Br23 Brn] Cl]2 Cl2] Brown Orange h 2 o 3408 m 3^05 s 3178 w 3112 sh C-H Stretch 2995 m 2988 s 3150 s 3031 m-sp 3067 s-sp 2995 sh 2920 w C-H (Side chain) 2350 m-b 2054 w 1883 w C=0 1790 s-sp| 1780 s ~ 1752 sh I 1750 sh _1 1731 sh 1720 sh TABLE 6 (Contd.) Assignment [Pt(P0X)2 [Pd(P0X)2 [Pd(POX)2 [Pd(POX) [Pd(POX-COCHo) [Pt(POX-COCH3 )2 3Cl2 Br23 Br2] Brn3 Cl32 Cl2 ] Brown Orange C=N 1633 w 1622 w 1647 sh 1630 sh 1615 w-b 1633 sh ^.cyclic) 1634 sh 1614 sh Band I 1615 sh 1610 m-sp 1595 s-sp 1601 m-sp 1604 s 1590 m-sp 1595 m-sp Band II 1562 w 1559 w 1566 sh 1567 sh 1565 w 1564 w 1551 sh -N=0 1524 sh 1523 sh 1528 sh 1517 s-sp 1509 s 1517 m _ 1505 sh 1500 sh Band III 1488 s-sp 1475 s 1476 m-sp 1490 s 1477 m-sp 1485 s-sp 1479 sh 1477 m 1446 w 1454 sh Band IV 1463 sh - 1460 sh 1455 s-sp 1435 m 1426 m-sp 1443 m 1436 sh 1448 sh 1448 sh 1425 sh 1426 s-sp 1428 s 1416 sh 1409 sh 1413 1416 sh _ 1401 sh 1396 sh 1394 shs 1J 1373 sh 1366 sh CH,CO side 1369 s-sp] 1360 s-sp chain 1356 m-sp] 1335 m-sp TABLE 6 (Contd.) Assignment [Pt(POX)P [Pd(P0X)o [Pd(P0X)o [Pd(POX) [Pd(POX-COCHL) [Pt(P0X-C0CHo)o ]ClP Br2 ] Br2 ] Brn ] Cl]2 ci2 ~ ’] 3 2 Brown Orange 1360 s-sp 1360 s 1349 s 1342 sh _ 1326 m-sp 1312 sh 1307 S~ 1299 s 1297 w-b 1298 m 1271 sh 1299 sh 1288 sh 1258 s-sp 1259 s 1251 s 1256 shl 1254 w 1250 m 1249 m j 1206 sh 1229 s' 1225 m 1227 s sh 1214 s-sp 1196 1216 sh. 00 1—I CO iH 1191 s _ 1190 s w-b 1173 vsl H 83 s-b 1160 m-sT5 1161 m"l 1161 sh_J 1162 s =N - 0 (?) 1149 sh _ 1152 s 1157 sh) 1148 m 1131 s i 1117 m-sp 1126 m 1125 sh] 1108 m 1117 sh 1101 s 1108 m 1111 m-s 1082 vs 1062 m 1064 sh 1061 m-vb 1068 w 1052 m _ 1052 sh 1045 m 1040 m 1037 m-sp 1043 m 1035 s i 1034 m 1021 sh- 1029 m 1017 sh 1017 sh 1008 w 1011 s 1009 s 993 w 1004 sh 988 sh 998 sh_ VO TABLE 6 (Contd.) Assignment [Pt(P0X)2 [Pd(POX)2 [Pd(POX)2 [Pd(POX) tPd(POX-COCH3) [Pt(P0X-C0CH3)2]Cl2 Br2 ] Br2 l Brn3 Cl]2 Clg] Brown Orange 978 s 981 m 983 m 961 s 959 sE 934 s-sp 949 S CO CO 896 sh CO m-b 826 s-1 853 sir 833 nf] 808 sh 841 s_ 828 sh 802 vw_ 776 sh C-H rock 778 s-b 776 s-1 776 s 767 m-b 773 vs 778 s 752 sh. 744 m 737 m 737 m 712 w 704 s 701 m C-H bend 678 s 672 s 684 m 676 w 668 m 673 s 667 m 668 sh 668 m 667 w 658 m 659 m 666 sh s = strong, m = medium, w = weak, b = broad, sh = shoulder, sp = sharp, v = very. X TRANSMISSION 100 40 20 60 80 4000 3000 2000 nrrd srto Setu f PKPOX^Brj] B ^ X O P K [P of Spectrum bsorption A Infrared 1500 RQEC (cm.-') FREQUENCY Figure 14 Figure 1000 900 800 100 8 0 - 60- 2 0 - Infrared Absorption Spectrum of [PdlPOXljBrj] 40 0 0 3000 2000 1500 1000 700 FREQUENCY (cm.*1) I0 0 r 8 0 # 6 0 - 4 0 - 20 infrared Absorption Spectrum of [Pd(P0X)2] and Br 2 Reaction Product 4 0 0 0 3000 2000 1500 1000 900 800 700 FREQUENCY (cm*') X TRANSMISSION % TRANSMISSION lOOr 100 60 - 0 4 - 0 8 20 - 0 4 - 0 6 80 0 2 - 3000 0 0 0 4 3000 0 0 0 4 J J ------I ___ L. I ___ L 2000 2000 J I 1 I 1 I I I -J I I L- I I I J nrrd bopin pcrm f P(O CH3CO)CI2] H -C [Pd(POX of Spectrum Absorption Infrared nrrd bopin pcrm f [Pd(POX)Cl]j of Spectrum Absorption Infrared 1500 1500 _____ RQEC (cm'1) m c ( FREQUENCY RQEC (cm*1) FREQUENCY _l 1 ______l_ L 00 900 1000 J I I -J 00 0 0 0 8 900 1000 ______L 0 700 800 700 U> ->1 % TRANSMISSION 100 - 0 4 0 6 8C- 0 2 - - 4000 3000 2000 nrrd bopin pcrm f [Pt(POX-COCH,), of Spectrum Absorption Infrared 1500 iue 17 Figure RQEC (cm.-') FREQUENCY 1000 900 800 100 % 40 TRANSMISSION 0 0 0 6 0 2 0 - - - 4000 nrrd bopin Spectrum Absorption Infrored 3000 2000 1500 RQEC (cm.*1) FREQUENCY Figure 18 Figure 1000 900 800 700 Gi 76 Pour assignments have been made for the aromatic ring in the spectral region usually associated with un saturation. These are identified simply as Bands I, II, III, and TV. In the ligand spectrum Band I appears at 1600 cm"1, Band II at 1569 cm"1, Band III at 14-77 cm”1, and Band IV at 14-39 cm"1. These peaks are all sharp and of strong intensity. In the spectra of the complexes of 2-pyridinaldoxime Band I appears over the range 1616 - - 1590 cm"1, in general close to the frequency observed for the ligand. This peak is sharp and of strong intensity in most of the spectra recorded; occasionally It is only of medium intensity. Band II in the spectra of the complexes appears in the range 1588-1553 cm"1, generally very near the position of this peak in the uncoordinated ligand (1600 cm”1). The intensity of Band II In the spectra of these complexes is usually weak, in contrast to the intensity observed for this peak in 2-pyridinal- doxime. In the spectra of compounds containing coordi nated ligand Band III appears in the region 1491-1469 cm"1, usually close to 1481 cm"1. As in the spectrum of the free ligand this band is sharp and of strong intensity in the majority of the spectra observed; it is only of moderate intensity in a few cases. The complexes studied exhibit Band IV In the spectral range of 1463-1424 cm”1, in general close to the frequency observed for this peak 77 in the ligand spectrum (1439 cm”1). This band is of variable intensity throughout the spectra studied, ranging from strong to very weak. These assignments are con- 41 sistent with those made by FIggins and with those of 20 Stoufer. In the three nickel(il) complexes containing co ordinated pyridine molecules, three additional band assign ments have been made. These were attributed to pyridine, and are called Band la, Band Ilia, and Band IVa. Band la appears as a shoulder on the low frequency side of Band I In the region 1589-1582 cm"1; Band Ilia, as a shoulder on the high frequency side of Band III in the region 1489- 1484 cm"1; and Band IVa (medium or shoulder), in the region 1422-1415 cm"1 . Band Ila, which should be near 1575 cm"1, could not be found. These assignments are consistent with those listed by Piggins for the pyridine r i n g . 2*'1 Three assignments were made in the low frequency extremity of the spectral range studied. A C-H rocking mode is present In the region 779-765 cm"1, generally close to 774 c m - '1'. This band is almost Invariably strong. A C-H bending vibration occurs in the region 907-885 cm"1, usually close to 894 cm"1 . It is of medium intensity. A second C-H bend has been assigned in the region 683- 665 cm”1 (close to 675 cm- '1' and medium or strong in intensity), 78 and in the region 670-658 cm-1 (near 665 cm”1 and variable in intensity). The assignment of this second C-H bending mode must remain tentative. These assignments are in agreement with those of Piggins, except that he observed only a single vibration in the region 680-650 cm"1. This second band appears in about seventy-five per cent of the spectra examined for the complexes of 2-pyridinaldoxime. In addition to these assignments the pyridine ring C-H stretching vibration has been assigned near 3100 cm”1, and the frequency associated with the side chain C-H, near 2800 cm-1. These assignments are also consistent with those made by Piggins and by Stoufer. In the region 1167-11^8 cm-1 (commonly near 1160 cm”'*') there is a band of variable intensity which may be an N-0 stretching mode. Blinc and Hadzi,19 in a study of the nickel(ll) and palladium(ll) complexes of dimethyl- glyoxime (and the monosodium and monopotassium salts of dimethylglyoxime), and the nickel(ll), palladium(il), platinum(ll), and copper(ll) complexes of cyclohexane-1,2- dione dioxime assign an N-0 stretch in the region 1260- 1210 cm”'*'. Borello and Henryk have assigned the 1150 cm”'*' band in dimethylglyoxime to the N-0 stretch. One would expect, however, that the presence or absence of the oxime proton would alter this band. On inspection, it is seen that this is not true in the case of the 1160 band in the 79 spectra of the complexes of HPOX. The position of this band is constant throughout the series of complexes. The intensity of the band is constant for the complexes con taining unionized ligand, but varies nonuniformly from strong to weak for the other complexes. Bellamy^ lists the C=N stretching frequency in alicyclic systems in the range 1690-1640 cm--*- with variable intensity. Piggins makes this assignment at 1634 cm--1- for pyridinal methylimine and over a range for several com plexes, The intensity of the C=N absorption in his com pounds varies from strong to weak. Stoufer makes this assignment near 1630 cm”-*-; his bands vary in intensity generally from strong to medium. Stratton,39 studying complexes of 2-pyridinaldazine, assigned this band near 1630 cm-1, the intensity varying from strong to weak. The acyclic C=N stretching mode has been assigned at 1625 cm-1 for 2-pyridinaldoximej this absorption is weak. For the complexes reported here this assignment has been made in the spectral range of 1661-1614 cm--*", with most of the spectra showing this absorption near 1635 cm-1. This band is one of particular sensitivity to steric and conjugative effects, as has been observed In liii by Piggins and by Stratton. It seems significant that this vibration is relatively intense and well-defined in most of the compounds which contain unionized ligand, 80 as well as In the free ligand. In compounds containing ligand from which an oxime proton has been removed, how ever, it appears only as a shoulder on the high frequency side of Band I, with few exceptions. The spectrum of 2-pyridinaldoxime has a strong peak at 1520 cm-1. This band disappears in complexes con taining neutral ligand (either unionized or acylated), but reappears in all complexes containing the anionic form of the ligand; e.g., the type [M(POX)(HPOX)]+ or [M(P0X)g], It lies in the region 1529-1500 cm"1 and consists of two or three closely spaced peaks (1529-1523 cm-1, 1522-1509 cm , and 1511-1500 cm )• In most of the spectra which contain this band there is one peak which is either strong or moderate in intensity. Since this band appears only in complexes con taining ionized ligand, or the ligand itself, it must be associated with the C=N-0” portion of the molecule. If one considers two resonance forms of the 2-pyridinal doxime anion (structure XXl), it becomes immediately H H "Q Cv XXI apparent that it is possible to have some contribution to the structure of the ligand from the -N=0 form. Unionized complexes would show little, if any, of this structure in the ligand. Uncomplexed ligand might involve hydrogen bonding in the crystalline state (structure XXIl) and, K XXII with a partial negative charge on the oxygen, one would expect contributions from the same resonance forms shown above (structure XXI). Significant also is the fact that complexes con taining acylated ligand have no significant absorptions near 1520 cm"^, Since these substances should involve no ionic resonance structures, one would expect no absorption in this region. This conclusion has been verified experi mentally. Bellamy tabulates a band of strong intensity for the R-N=0 group in the spectral region of 1600-1500 cm-1. The postulate of a C-N=0 contribution in some of the 82 complexes studied Is consistent with this earlier assign ment . The two acylated complexes (see Section II), [Pd(POX-COCH3)Cl2] and [Pt(P0X-C0CH3)2]Cl2, have medium intensity, sharp absorption maxima at 1356 cm"-1- and 1335 cm-*, respectively. These compounds also have strong, sharp peaks at 1369 cm"’* and 1360 cm-*. Bellamy^ lists an absorption attributable to the side chain CH^CO group at 1356 cm-*, and this assignment has been made for these two compounds. The position of the C=0 band in the acylated complexes is unusually high, at 1790 and 1780 cm-*. This band Is sharp and quite Intense, being one of the strongest in the spectra. It is almost too high in frequency for the type linkage proposed, being very close to the C-0 band in acetyl chloride (1802 cm-*).2^ Bellamy2*^ observes that the frequency of the carbonyl peak shifts to higher values as more electro negative groups are attached to the carbonyl carbon. If one considers the oxime oxygen to be a strongly electro negative group, just somewhat less so than the chloride In acetyl chloride, the observed frequency for the carbonyl peak in the acylated complexes appears to be more reasonable. This is comparable to saying that the bond between the carbonyl carbon and the oxime oxygen Is highly polar. 83 Also unusually high, and unusually broad, are the C=0 bands in the acetato complexes, [Ni(HPOX)g (C^H^C^Jg] and [Ni(P0X)(HPOX)(C2H302)(H2O)3, at 1760 and 1772 cm-1, respectively. These peaks are of medium intensity, Bellamy lists a frequency of 1760 cm”1 for the C=0 band in the monomer of alkyl acids and a strong vibration in the range 1750-1735 cm"*1 for normal saturated esters. The ionized carboxyl group appears at a much lower frequency, in the range 1610-1550 cm”1. Morris and B u s c h , ^5 a study of some cobalt(ill) complexes of ethylenediaminetetraacetic acid (and its salts) assign the C=0 band in the range 1658- 1648 cm”1 for the COO-M group, in the range 1750-1745 cm”1 in the COOH group, and in the range 1604-1600 cm”1 for the COO” group. This tempts one to propose that the acetate which is present in the 2-pyridinaldoxime complexes is present as acetic acid. This is inconsistent with the low conductivity observed for [Ni(POX)(HPOX)(CH^COO)(HgO)] in methanol, (32,0 ohms”1), and with the magnetic moment which indicates an octahedral structure. Also,the infra red spectrum of the diacetato complex, [NitHPOXjgfCgH^Og)^, does not have a band near 1500 cm”1, which should be present in such a species if the oxime proton were removed from a ligand molecule,(and combined with acetate to form acetic a c i d ) . 84 Another possible explanation of the unusual position observed for the C=0 vibration in the spectra of the acetato complexes is that the metal to oxygen bond is very covalent, i.e., the ionic contribution is extremely small, in such a case one might expect this frequency to occur near 1750 cm-'*- as in esters. This would imply that the COO-M link in all other compounds examined has been relatively ionic. Most of the bands which persist through the com pounds examined have been assigned. One persistent band, occurring near 1250 cm“^, with variable intensity, remains unassigned. II. REACTIONS OF NICKEL(II), PALLADIUM (II), AND PLATINUM(IT) COMPLEXES OF 2-PYRIDINALDALDOXIME AND DIMETHYLGLYOXIME A. Introduction The reactions of coordination compounds may all be classified as belonging to three different categories. The first category Involves substitution of one ligand by another, the second category involves reactions of the central metal atom only, i.e., oxidation or reduction, and the third category, reactions Involving coordinated ligand, i.e., oxidation of the ligand, substitution on the ligand, etc. Reactions which involve the replacement of one ligand by another (the first category) have been known for many years. They are not discussed In this dissertation Insofar as they are not involved with the other two categories. Examples of the latter two categories of reactions are of Immediate concern here. The reaction of the central metal atom which is reported here is oxidation with halogen, in particular with bromine; the reactions of coordinated ligand which are dealt with are those involving substitution on the oxime group. These re actions are discussed below. 86 1. Reactions of Coordinated Ligand.— One might suspect that an oxime oxygen, particularly one bearing a negative charge, would be readily attacked by acyl halides to form the corresponding oxime esters. When the oxime nitrogen Is coordinated to a metal it Is diffi cult to predict the reaction products; a stable complex may be formed by the oxime ester, a mixture of metal salt and oxime ester may be obtained, or a much more complex mixture may result. kf. Sharpe and Wakefield have studied the reaction of [Ni( HDMG)2C12 ] with acetyl chloride, and claimed to have obtained a complex containing acylated ligand, [Nl(DMG-COCHg)2Cl2 3. They also claimed that, In the presence of hydrogen chloride, [Pd(DMG)2 ] yields [Pd(HDMG)2Cl2] which acylates to form [Pd^MG-COCH^^Clg]. The reaction with the palladium compound was refuted a oh short time later by the same authors, but they retained their opinion on the nickel system. At approximately the same time that Sharpe and Wakefield were conducting their Investigations, Jicha and Busch‘S also studied the nickel system. The latter authors found that a stable, acylated complex does not form; the product consists of [Ni(HDMG)Cl2] (structure XV on page 12) and dlaeylated ligand (structure XXIII). Jicha and Busch examined the system by means of infrared spectroscopy and by separation and purification of the products. There seems to be little doubt that Sharpe and H3C-C-O-NC-O-N N-O-C-CH. '3 XXIII Wakefield-'s observations on the nickel system are erro neous . The only other workers to attempt reactions of this sort are Thilo and Friedrich, ^ who reacted [Nl(DMG)2 ] with dimethyl sulfate and methyl iodide. The products are the methyl diether of dimethylglyoxime and nickel salts. No nickel complex with the diether could be prepared except when alcohol was used as the solvent. 2. Reactions of the Central Metal Atom with Halogens.— It has been known for many years that the central metal atom in most platinum(ll) complexes and many palladlum(ll) complexes may be oxidized to the +4 oxidation state. Tschugaeff^ noted that platinum dioximes easily add bromine to give compounds of the type [Ptl^jBrg] (where L 88 is a bldentate uninegative anion). Morgan and Burstall^1 used chlorine to oxidize [Pt(bipy)2 ]Cl2 to [Pt(bipy)2Cl2 ]Cl2, and Livingstone^® observed that [Pd(blpy)Cl2 ] is readily oxidized by chlorine to [Pd(bipy)Cl^]. Since platinum(lV) enjoys a fair degree of stability, the oxidation of [Pt(DMG)2] and [Pt(P0X)2 ] to the platinum(lV) species should proceed readily. Palladium(lV), being somewhat less stable, should show less tendency to form the corresponding tetra- valent derivatives. Consequently, oxidation reactions would proceed less easily with palladium(il) than with platinum(ll). There are few examples of nickel complexes in which the central metal atom exhibits an oxidation state greater than two. Several nickel oxime complexes have been pre pared in which nickel is claimed to possess a higher oxi dation state than usually observed; most of this work has been refuted. Hofmann and Ehrhardt l i f t prepared a hexa- formoximonickelate, as the trisodium salt, in which nickel(ill) was proposed as the central metal ion. Sacco 2lQ and Freni^-7 have recently shown this material to be a dia magnetic nickel(II) complex, containing only two sodium ions. Dubsky and Kuras^® claimed nickel(ill) to be present in a benzamide oxime complex which they prepared. Several years later Malatesta and Monti^1 were able to show that this complex contains nickel (il). Edelman52 and 89 Okac and Simek-^ claimed to have prepared nickel(ill) complexes of benzyldioxime. These claims were based principally on analysis; no magnetic data or infrared spectra are reported. One other nickel-oxime complex in which the central metal atom supposedly displays an oxidation state greater than two has been observed. Feigl^ first noted that, at high pH, an aqueous solution of [Ni(DMG)2 ] gives an intense red color on treatment with an oxidizing agent (lead dioxide). Since then, several procedures have been developed for the determination of small amounts of nickel utilizing Feigl's reaction, but employing bromine as oxidant.55.56,57,58 Several years later, in 1956, Kudo^9 examined a system similar to Feigl's using a large excess of lead dioxide. The highly colored filtrate obtained by Kudo was evaporated to dryness and nickel(IV) was claimed to exist in the black powder on the basis of iodometric measurements. In 19^8, however, Okac and Polster^® showed that Feigl's red precipitate contains lead as a principal constituent. They went on to point out^1 that in strongly alkaline solution oxidation sets In slowly without the addition of oxidizing agents. Consequently, it Is the ligand and not the nickel which is oxidized. /To Babko studied the [Ni(DMG)23-bromine system spectrophotometrlcally and also arrived at the conclusion that the ligand and not the nickel Is oxidized. Kuras and Ruzicka,^ by isolating compounds from various mixtures of nickel chloride, dimethylglyoxime, and bromine water in ethanol, arrived at the same conclusion, and finally Okac, from a potentiometric study of this system, agreed that the ligand Is oxidized and the nickel remains as nickel(ll). During the short interval in which claims were made that the nickel remains in the +2 state in this system papers began to appear in which the postulate was advanced that the nickel atom is oxidized. H o o r e m a n ^ conducted spectrophotometric studies and arrived at the conclusion that two species are formed by the Interaction of "peroxidized" nickel and dimethylglyoxime. One of the species was claimed to be an unstable material with a 2:1 ratio of ligand to nickel. The second, more stable substance, was reported with a 4:1 ratio. No compounds were isolated and he did not attempt to elucidate the nature of these species. Booth and Strickland^ concurred with Hooreman on the mole ratio In these compounds; these authors went on to determine the number of electrons re moved In the reaction (by a spectrophotometric method) and the number of equivalents of base required, by a 91 titration method. They concluded that the nickel Is oxidized; their formulations, however, are not in keeping with modern concepts of inorganic chemistry. Yatsimirskii and Grafova,67 m a spectrophotometric study of ammoniacal solutions of nickel(il) and dimethyl glyoxime in the presence of atmospheric oxygen, claimed the existence of a highly colored compound with a ligand to metal ratio of 3:1 and a colorless compound with a 1:1 mole ratio. Nadezhina and Kovalenko^® studied a similar system by spectrophotometry in the presence of several different oxidizing agents and claimed the existence of nickel(lll) in the complex [Ni^MG)^]. Two years later Peshkova and Mel 'chakova^ performed what apparently were similar experiments and arrived at the same conclusion as that deduced by Nadezhina and Kovalenko.^® At approximately the same time Yamasaki and Matsumoto^® also studied this system with the use of spectrophotometry and claimed to have observed the presence of the nickel(TV) complexes, [NlCDMG-H^NH^^l an<3 [Ni(DMG-H)^]” • (Here, DMG-H represents HDMG with both oxime protons removed to form the dinegative anion.) In 1956 Babko^1 published his second paper on this subject, in which he stated that these systems yield com plexes of either nickel(ll) or nickel(lll) with partly 92 oxidized dimethylglyoxime. He claimed that the inter mediate oxidation product of dimethylglyoxime forms a red solution on the addition of nickel(ill) hydroxide. Quite recently Okac and Simek have published three papers on this subject. By reacting a suspension of [Ni(DMG)2 ] in carbon tetrachloride with bromine,^3 a compound of the composition [Ni(DMG)2Br2 ] (verified by nickel, nitrogen, and bromine analysis) is formed as a black, amorphous powder. In a second paper^2 these authors propose the formation of nickel(IV) on the basis of spectrophotometric measurements. They claim that [Ni(DMG)2 j Is oxidized quickly according to the equations [ (DMG-H)Ni(OH)]" + 2 (DMG-H)= [NifDMG-H^]"^ + OH (NI(DMG-H)3 ]_2f -2e” [NITV(DMG-H)3 ]"2 Oxidation of the alkaline solution with oxygen is reported to proceed slowly with the oxidation of dimethylglyoxime. In the third paper^ these authors investigated the re duction of solutions of [NItv(DMG-H)3 ]-2 by potentiometric and photometric methods and claimed that the reaction [NI(DMG-H)3 ]~2 + 2e [NiII(DMG-H)3 3“if Is reversible. The dominant opinion at the present about the [Ni(DMG)g]-bromine system appears to be that the nickel 93 is oxidized. All the authors who originally postulated that only the ligand is oxidized, with the exception of Kuras and Ruzicka,63 have since published papers in which it is stated that it is nickel which undergoes oxidation. Unfortunately, only in a very few instances have compounds been isolated, and these have not been adequately charac terized. In this section of the dissertation two types of reactions are studied. The first type is the reaction of coordinated 2-pyridinaldoxime with organic reagents containing active halogen. Also the work of Jlcha and Busch^ has been extended to include the reaction of acetyl chloride with [Pt(DMG)2 ], The second type of reaction studied is that of coordinated metal ions with bromine. This includes the reactions of the platinum(ll), palladium(ll), and nickel(ll) complexes of 2 -pyridinal doxime as well as those of the platinum(ll), palladium(ll), and nickel(il) complexes of dimethylglyoxime. B. Experimental 1. Preparation of Dimethylglyoxime Complexes. Preparation of [Pt(DMG)g3.— Potassium tetrachloro- platinite was dissolved in water with a small quantity of hydrochloric acid and an alcoholic solution containing two 94 equivalents of dimethylglyoxime was added. The solution was heated to boiling and allowed to cool. The blue solid was removed by filtration, washed with water, and dried in vacuo over P2°5* Anal» Calculated for [ Pt (C^HyN2 C>2)2]: C, 22.58; H, 3.32; N, 13.17. Found: C, 22.57; H, 3.48; N, 13.27. Preparation of [PdfDMG)^].--Potassium tetrachloro- palladite was dissolved in water with a small quantity of hydrochloric acid and an alcoholic solution containing two equivalents of dimethylglyoxime was added. The yellow precipitate was allowed to stand for two hours and then removed by filtration, washed several times with water, and dried in vacuo over P^O . Anal. Calculated for ------2 5 ---- [Pd(CifH7N202 )2]: C, 28.52; H, 4.19, N, 16.63. Found: C, 28.71, 28.37; H, 4.31, 4.20; N, 16.46, 16.72. (Analysis on two separate samples.) Preparation of [N1 (DMG)2 3.— Nickel chloride 6 - hydrate was dissolved in water and an alcoholic solution containing two equivalents of dimethylglyoxime was added. A small quantity of ammonium hydroxide was utilized to raise the pH to the neutral point. The red solid was removed by filtration, washed thoroughly with water, and dried in vacuo over P205* 95 Preparation of [NifHDMOr^Br?].— Two and eighty-four hundredths grams of nickel bromide was dissolved in 50 ml, of hot absolute ethanol to which 10 drops of concentrated hydrobromic acid had been added. A solution of 2.8 g. of dimethylglyoxime in 100 ml. of hot absolute ethanol (con taining 20 drops of concentrated hydrobromic acid) was added to the nickel bromide solution. The total volume was reduced to 40 ml. by allowing the solution to digest on the hot plate. On cooling in the refrigerator over night, a crop of green crystals was obtained. Filtration and subsequent washing with a solvent consisting of 50 ml. of absolute ethanol and 10 drops concentrated hydrobromic acid yielded 0.93 g. of solid. Anal. Calculated for [Ni(C4H8N202 )2Br2]: C, 21.315 H, 3.58; N, 12.43; Br, 35.46. Found: C, 21.27; H, 3.82; N, 12.81; Br, 31.90. Nl(HDMG)Clo*HgO.— A sample of this material was kindly given to the author by Mr. Donald C. Jicha. 2. Reaction of 2-Pyrldlnaldoxlme Complexes with Bromine. Reaction of [Pt(P0X)gl and Bro.— Five tenths gram of [Pt(P0X)2 ] (0.00114 mole) was dissolved In 75 ml. of boiling chloroform, and seven drops of bromine was added (a slight excess over 0.00228 equivalent ). Immediately a red precipitate formed. After standing over night, the 96 solid was removed by filtration, washed with two portions of chloroform, and dried in vacuo over P2°5* Yield: 0.65 g. ( 95 per cent). Anal. Calculated for [Pt(CgH^N20)2Br2]: C, 24.13; H, 1.69; N, 9 .3 8 ; Br, 26.76. Pound: C, 24.01, 24.02; H, 1.64, 1.82; N, 9*50, 9-17; Br, 2 7 .18, 27.00. (Analysis performed on separate preparations.) Reaction of [Pd(P0X)_3 and Br2 fcellow Product).— One tenth gram of [Pd(P0X)2 ] (0.000287 mole) was dissolved in 500 ml. of hot chloroform. Pour drops of bromine (0.00144 equivalent ) dissolved in 25 ml. of chloroform was added. The dark brown solution which formed was allowed to digest on the hot plate for a few minutes. During this time the color changed to orange. The solution was allowed to evaporate to approximately 70 ml. After standing over night, there was a crop of fine, orange needles. These were separated by filtration, washed with a small amount of chloroform, and dried in vacuo over P20^. Yield: 0.08 g. Anal. Calculated for Pd(CgH5N20)2Br^: C, 21.49; H, 1.80; N, 8 .3 6 ; Br, 47.67. Pound: Sample A; C, 21.26; H, 1.73; N, 8.31; Br, 47.92. Sample B; C, 20.35; H, 1.75; N, 8 .3 2 ; Br, 45.30. Sample C; C, 15.70; H, 1.47; N, 5.33; Br, 56.86. (Three different preparations). Reaction of [Pd(POX)2 3 with Bro (Brown Product) Five tenths gram of [Pd(P0X)2] (0.00143 mole) was dissolved in 200 ml. of chloroform and filtered to remove any in soluble material. Eight drops of bromine (a slight excess over 0.00286 equivalent ) was added; immediately a dark brown precipitate formed. This was allowed to digest a few minutes on the hot plate and then set aside for three hours. The brown solid which formed was collected by filtration, washed twice with chloroform, and dried in vacuo over P2°5 * Yield: 0.49 g. Anal. Calculated for [Pd(C6H5N20)2Br2 ]: C, 28.32; H, 1 .98; N, 11.01; Br, 31.41; Pd, 20.97. Pound: C, 28.30; H, 2.06; N, 11.02; Br, 31.17; Pd, 21.11. 3. Reaction of Dimethylglyoxime Complexes with Bromine. Reaction of [Pt(DMG)2 3 with Bromine.— Five tenths gram of [Pt(DMG)2 ] (0.00118 mole) was mixed with 500 ml. of chloroform and five drops of bromine (0.00204 equivalent) and refluxed for 24 hours. At the end of this time the pot was allowed to cool to room temperature, the solution filtered to remove undissolved starting material, and the filtrate evaporated to a few ml. in vacuo. This mixture was filtered to give a green solid which was shown by paper chromatography (elution of the band with chloroform) to consist of a yellow phase and a blue phase. The green solid was dissolved in chloroform, adsorbed on filter paper, and the paper washed with chloroform to give an orange filtrate. On evaporation to low volume the filtrate yielded orange-yellow crystals. Anal. Calculated for [Pt(C4H7N20 2 )2Br2 ]: C, 16.42; H, 2.4l; N, 9.57; Br, 27.31. Pound: C, 16.38; H, 2.52; N, 9.35; Br, 27.51 Reaction of [Pd(DMG),-J with Bromine.--Five tenths gram of [Pd(DMG)g] (0.00148 mole) was dissolved in 500 ml. of chloroform, ten drops of bromine (0.00406 equivalent) were added, and the solution was refluxed for 20 hours. After cooling to room temperature, the solution was fil tered to yield orange crystals, which were washed with chloroform and dried in vacuo over P„0,-. Yield: 0.28 e . ------2 5 of [Pd(HDMG)Brg3 (49.4 per cent). Anal. Calculated for [Pd(C4H8N202 )Br2 ]: C, 12.55; H, 2.11; N, 7.32; Br, 41.77. Pound: C, 12.48; H, 2.08; N, 7.70; Br, 41.45. Reaction of [Ni(DMG),-J with Bromine.—"amm m m One and five tenths grams of [Ni(PMG)^] (0.00519 mole ) was mixed with 500 ml. of chloroform, 0.70 ml. of bromine (0.0260 equiva lent ) was added, and the solution was refluxed for 23 hours. The solution was allowed to cool to room temperature and filtered. The green solid obtained in this way was washed with chloroform and dried in vacuo over P20^. Yield: 0.90 g. Anal. The analysis observed is compared with the theoretical values for two possible products and a mixture 99 of the two: c H N Br Ni(HDMG)2Br2 21.31 3.58 12.43 35.46 Ni(HDMG)Br2 14.36 2.41 8.38 47.76 0.496[Ni(HDMG)Br2 ] + 0.504[Ni(HDMG)2Br2 ] 17.85 3.00 10.42 40.54 Observed 17.87 3.73 10.39 41.03 The red filtrate was evaporated to low volume and filtered to obtain an additional 0.24 gram of green solid. The filtrate was red, had a strong smell, and was a lachrymator. No clean compound could be Isolated from this red solution. 4. Reaction of Complexes with Reagents Containing an Active Halogen. Reaction of [Pd(POX)23 with Acetyl Chloride.— One and seven hundredths grams of [Pd(P0X)2 ] (0.00307 mole) was dissolved in 250 ml. of hot chloroform, filtered to remove any undissolved material, and one ml. of acetyl chloride (a two fold excess over 0.00614 equivalent ) was added to the warm solution with stirring. The color of the solution immediately changed from yellow to orange. Precipitation started within 30 seconds and, after five 100 minutes, the yellow solid was collected by filtration, washed thoroughly with chloroform, and dried in vacuo over Yield: 0.91 g. This solid was recrystallized from hot nitro benzene and dried in vacuo over P2O5 at 78°C. Yield on recrystallization, 84 per cent. Anal. Calculated for [Pd(C6H5N20-CH3C0)Cl2 ]: C, 28.11; H, 2.36; N, 8.20; Cl, 20.75. Found: C, 2 8 .09, 28.16, 2 7 .83; H, 2 .37, 2.48, 2.54; N, 8.10, 8 .98, 8.24; Cl, 20.55, 20.71, 20.07. (Analyses performed on different preparations.) Reaction of [Pt(P0X)2 ] with Acetyl Chloride.— One gram of [Pt(P0X)2 ] (0.0029 mole) was dissolved in 150 ml. of boiling chloroform; 0.4 ml. of acetyl chloride (a slight excess over 0.00458 equivalent ) was added and the brown solution immediately turned yellow. The solution was placed in the freezer compartment of a refrigerator over night. It was then filtered and the solid was washed v several times with chloroform and dried in vacuo over P205 . Yield: 0.50 g. The solid appears to be a mixture of yellow and orange solids. A sample was mixed with warm dimethylformamide and filtered to give a yellow solid, (Yield: 45.7 per cent) and an orange filtrate. Anal, of solid. Calculated for [Pt(CgH^^O-CH^CO^lClrj: C, 32.32; H, 2.71; N, 9.43; Cl, 11.93; Pt, 32.84. Found: C, 32 .98; 101 H, 3-40; N, 8.89; Cl, 11.90; Pt, 31.59. The filtrate was evaporated to dryness to give an orange solid. Anal. Pound: C, 20.74; H, 2.32; N, 9.01; Cl, 16.42. Reaction of [Pd(P0X)2 ] with Benzoyl Chloride.— Ninety-five hundredths gram of [Pd(P0X)2 ] (0.00272 mole) was dissolved in 200 ml. of hot chloroform and filtered to remove any undlssolved material. Eight tenths of a milli liter of benzoyl chloride (a slight excess over 0.00344 equivalent ) was added; the solution turned orange and precipitation started after 30 seconds. After standing for 10 minutes, the orange-yellow solid was collected by filtration, washed thoroughly with chloroform, and dried in vacuo over P20j-. Yield: 0.96 g. (theoretical 1.18 g). On recrystalllzatlon from nitrobenzene a material is ob tained which, under the microscope, appears to be a mix ture. Anal. Calculated for Pd(CgH^N20-C0CgH^)Cl2 : C, 35.95; H, 2.32; N, 6.45; Cl, 16.33; Pd, 24.57. Pound: C, 41.53; H, 2.88; N, 7.99; Cl, 15.92; Pd, 23.25. Reaction of [Pd(P0X)2 ] with Benzyl Bromide.— Five- tenths gram of [Pd(P0X)2 ] (0.00143 mole) was dissolved in 200 ml. of chloroform and 0.4 ml. of benzyl bromide (a slight excess over 0.00286 equivalent ) was added. The solution was refluxed over night during which time the 102 color of the solution changed from yellow to cherry red. The chloroform was evaporated to a volume of 20 ml.; this gave a mixture of yellow needles, which appeared to be starting material, and red crystals. The yellow solid was removed by extraction with chloroform; to remove the red material it was necessary to scrape the solid from the walls of the flask with a spatula. The red crystals were dried in vacuo over P2 C>5 * Anal. Calculated for [Pd(C6H5N20-CH2C6H5 )2 JBr2 : C, 45.19; H, 3.50; N, 8.11; Fr, 23.13. Found: C, 48.01; H, 4.12; N, 6.32; Br, 29.50. Reaction of [Pt(DMG)23 with Acetyl Chloride. The Preparation of [Pt(HDMG)Cl2] .--Five tenths gram of [Pt(DMG)2] (0.00118 mole) was mixed with 300 ml. of chloro form; 20 ml. of acetyl chloride (a hundred fold excess) was added, the mixture was boiled for 30 minutes, and allowed to stand over night. The yellow-brown solid was collected by filtration, washed thoroughly with chloroform and dried in vacuo over P2°5* Yield: 0.44 g. (theoretical, 0.45 g.). Anal. Calculated for [Pt(HDMff)Cl2 ]: C, 12.57; H, 2.11; N, 7.33; Cl, 18.55; pt, 5 1 .07. Found: C, 12.57; H, 2.16; N, 7.49; Cl, 1 8 .38; Pt, 5 0 .9 5 . The Hydrolysis of [PdfPOX-COCH-^C l o ].— Twenty five hundredths gram of [PdtPOX-COCH^C^] was mixed with 20 ml. 103 of warm water. Dilute sodium hydroxide was added in small portions until all solid was dissolved and apparently hydrolyzed, as indicated by the pH remaining constant at a value of 8. The solution was filtered and dilute hydro chloric acid was added to the filtrate until it was strongly acid. On lowering the pH, a flocculent yellow precipitate formed. After three hours, the product was collected by filtration, washed twice with water, and dried in vacuo over P2°5 » 0.20 g. (theoretical, 0.19 g.). Anal. Calculated for [Pd(CgH^N20)Cl]: C, 27.37 H, 1.91; N, 10.64; Cl, 13.47. Found: C, 27.07; H, 2.50; N, 10.14; Cl, 13.27. 5. Physical Methods. Measurements performed on the compounds reported in this section were made with the same equipment described in Section I. One additional technique, paper chromato graphy, was found to be helpful in the study of the dimethyl glyoxime complexes discussed above. By the use of a Whatman number 1 paper strip, a standard glass chromatography jar, and chloroform as eluting agent (with the descending solvent technique) it was found that the uncharged dimethylglyoxime complexes ([M^(DMG)2 J) could be separated from their reaction 104 products by this method. A chloroform solution of the mixture to be examined was placed on the paper strip, allowed to dry, placed in the jar and eluted with chloro form. After a few hours the uncharged complex, [M-*--1-(DMG^l, had made no perceptible progress down the strip, while the reaction products proceeded almost with the solvent front. Attempts were made to separate larger quantities of material by the use of a powdered cellulose column. This technique was not particularly successful because of experi mental difficulties, i.e., nonuniform packing of the column. However, with a minimum expenditure of time the experi mental difficulties encountered in the use of a cellulose column for the separation of coordination compounds should be overcome. One great advantage to this method is that these compounds are "self-developing." The separation of the highly colored compounds may be followed visually. Analyses.— All analyses on the compounds reported in this section of the dissertation were performed by Schwarzkopf Microanalytical Laboratory. C. Results and Discussion Despite the great volume of work which has been performed on the synthesis and characterization of coordi nation compounds relatively little has been reported on 105 the reactions of coordinated ligands. The work dealt with in this section of the dissertation consists ex clusively of the reactions of complexes, and although it is primarily exploratory work, several very interesting reactions have been observed. The reaction of [Pt(DMG)2 ] with acetyl chloride has been found to proceed in a manner analogous to that previously observed for the corresponding nickel(il) and palladium(ll) compounds. The studies on the reactions of coordinated ligand with acetyl chloride have been extended to the 2-pyridinaldoxime system. Acetyl chloride has also been observed to react with [Pt(P0X)2 ], [Pd(P0X)g], and [Ni(P0X)2 ]; these compounds, however, give a much different type of product than that obtained from the [M-1--3-(DMG)2 3 systems. Benzoyl chloride and benzyl bromide were found to react with [Pd(P0X)2 ]; these systems, however, were incompletely explored. The bromination reactions studied in this work proceed in a manner depending on the nature of the co ordinated metal and consistent with the tendency of the metal to be oxidized. Complexes of the type [M^(P0X)2Br2 ] are readily prepared with platinum or palladium; such a species however is not formed with nickel. The reaction of [Pt(DMG)2 ], [Pd(DMG)2], and [Ni(DMG)2 ] with bromine also has been studied. Platinum goes to the 44 oxidation 106 state whereas the palladium and nickel compounds lose dimethylglyoxime through its oxidation. These reactions are considered in detail below. 1. Reactions with Compounds Containing Active oh. Halogen.— Sharpe and Wakefield were the first authors to make the claim that a coordinated oxime ligand had been acylated and not removed from the coordination sphere; the compounds studied were [Ni(DMG)2 ] and [Pd(DMG)23. Later they refuted their work on the palladium compound but maintained their views on the reaction with the nickel 2 C > compound. Jicha and Busch, however, have shown that [NifDMGjg] and [Pd(DMG)2 ] in their reaction with acetyl chloride form complexes of the type [M11(HDMGjClg]; the ligand which is lost is diacylated. In the present work it has been found that [Pt(DMG)2 3> on reacting with this reagent, gives the same type of complex as that obtained in both the nickel and palladium systems, i.e., [Pt(HDMG) Cl2 ]. This compound is prepared in essentially quanti tative yield, in what appears to be a high degree of purity as indicated by elemental analysis. The infrared absorption spectrum of [Pt(HDMG)C123 is nearly identical with that of the similar compound, [Pd(HDMG)Br2] (Figure 22), prepared by a different procedure; both of these compounds give spectra which are very similar to that of [Ni(HDMG)Cl2]‘H20 (Figure 23 ). 107 Acetyl chloride quickly reacts with [Pd(P0X)2 ], apparently according to the equation [Pd(POX)2 3 + 2 AcCl --- » [Pd(P0X-Ac)Cl2 ] + POX-Ac. The ligand presumably acylates on the oxime oxygen to form the oxime ester (structure XXIV). XXIV This constitutes the first example of a coordinated oxime ligand being acylated without its removal from the complex. The resulting compound, [Pd(POX-Ac)C12 1, shows a fair degree of stability. It may be recrystallized from hot nitrobenzene without decomposition. On dissolving in aqueous sodium hydroxide, however, the acetyl group is removed. The addition of hydrochloric acid to the re sulting solution then causes [Pd(P0X)Cl]2 to be precipi tated. This last compound has been formulated with a dimeric structure involving chloride bridges (structure XXV) in order to satisfy the coordination number of four for palladium. When the platinum compound, [Pt(POX)2 3 is treated with acetyl chloride, the diacylated complex, 108 [Pt(POX-Ac)2]C12* is obtained. It was expected that this compound would be completely analogous to the acylated XXV palladium complex; the fact that chloride apparently does not displace one mole of ligand seems to be quite unusual. In this reaction it may be solubility which ultimately determines the product to be formed. This would be es pecially true if the mechanism of the acylation involved formation of the diacylated species [M^^OX-Ac )2]++ first, one mole of acylated ligand then being replaced by chloride in the case of the palladium complex. The infrared ab sorption spectra of the acylated complexes, and their sig nificance, have been discussed above and are recorded in Figures 16 and 17. A product has been obtained from the reaction of benzoyl chloride with [Pd(P0X)2]. The infrared absorption spectrum of this material shows a strong carbonyl peak at 1756 cm”1 (Figure 18); no simple compound may be formulated from the analysis, however. The reaction of [Pd(P0X)2 ] with benzyl bromide likewise gives a material which has not been formulated. 109 It is important to note that 2-pyridinaldoxime forms ethers and esters which give stable coordination compounds; the diethers and diesters of dimethylglyoxime do not form such stable complexes, but coordination com pounds of the monoether are known.^ The important factor appears to be monosubstitution, if stability is to be attained. 2. Reactions with Bromine.— The complexes of 2- pyridinaldoxime react with bromine in a manner dependent on the metal atom present, m keeping with the fact that platinum exhibits a very stable +4 oxidation state, [Pt(P0X)2 ] quickly reacts with bromine to form the platinum (IV) complex, [Pt(POX)2Br2 ]. The infrared absorption spectra of reactant and final product are very similar (Figures 13 and 14) indicating that the central metal atom, and not the ligand, is oxidized. The analysis of this compound indicates the proposed constitution to be correct. Palladium forms compounds in the +4 oxidation state which are somewhat less stable than those of platinum(lV). When [Pd(P0X)2 ] is reacted with bromine, a brown solid, [Pd(P0X)2Br2 ], results. Again, the infrared absorption spectra of the related complexes are very similar (Figures 12 and 15). It is interesting to observe that in both the 110 platinum(IV) and palladium(TV) complexes of the type [M-^POXjgBrg]» the infrared spectra are considerably sharper than those of the original complexes. The palladium(iv) complex is not as stable as the corresponding platinum compound. If the bromine oxidation is carried out in very dilute chloroform solution no brown solid is precipitated; eventually an orange or yellow material is obtained. Analyses of these light-colored samples indicate the presence of large amounts of bromine. The infrared absorption spectra of these oxidation products (Figure 15) show much less similarity to [Pd^OX)^] than does [Pd(POXjgB^]. One concludes that attack on the ligand occurs much more easily in the palladium system than in the platinum system. From these observations, and from what is generally known of nickel complexes, one would not expect the for mation of stable, high oxidation state nickel derivatives with HPOX. This was experimentally verified. Treatment of chloroform solutions of [Ni(P0X)2] yields only oils. Similar treatment of the platinum(ll), palladium (il), and nickel(il) complexes of dimethylglyoxime gives slightly different results than those observed in the HPOX system. It was felt that a systematic study of the bromine reaction with compounds of the type [Mt i (DMG)2 ] would be quite illuminating. One would be able to extrapolate from Ill platinum to palladium to nickel and in this manner perhaps be in a more advantageous position to discuss the oxidation of [Ni(DMG)2 ]. This was found to be true. [Pt(DM5)2 ] yields the platinum(lV) complex, [Pt(DMG)2Brg]. As in the 2-pyridlnaldoxime system, the infrared absorption spectra of reactant and product are very similar (Figures 19 and 20). Treatment of [Pd(DMG)2 ] with bromine in chloroform at 60° C. results in the precipi tation of [Pd(HDMG)Br2 ] and not the palladium(rv) deri vative. The composition proposed has been confirmed by analysis; moreover, the infrared absorption spectrum of this compound (Figure 22) is very similar to that observed for [Pt(HDMG)Cl2] and [Ni(HDMG)C12 ]‘HgO (Figure 23). When the chloroform filtrate is evaporated to dryness, there is a very strong odor and the yellow solid which is obtained appears to be a lachrymator. At this point it might be well to consider some observations made on a dimethylglyoxlme-bromine-chloroform mixture. On mixing dimethylglyoxime with bromine and chloro form, a reaction occurs. Evaporation to low volume causes the evolution of white fumes. The low pH of the solution and the fact that the fumes cause a precipitate to form in a drop of silver nitrate held above the beaker lead to the conclusion that hydrobromic acid is formed in the reaction. On neutralization with potassium carbonate the solution 112 retains a very strong odor; the addition of a nickel(II) salt does not create the characteristic red color of [Ni(DMG)2 ] but instead a tan solid forms. These results lead one to conclude that dimethylglyoxime is indeed oxi dized by bromine. De Paolini^*75 has studied the reactions of several oximes with bromine. He postulates a reaction of the type Br? . , , -HBr f RR'C=NOH ---% RR CBrN(OH)Br ■ - ■ > RR CBrNO which is dependent on the nature of the R and R 1 groups. In the same reaction, with certain o^-dioximes of the general type HOC(:NOH)C(:N0H)C02H, he has obtained a product which appears to be Br2C=N0H. It is difficult to say exactly what the product would be in the bromine re action with dimethylglyoxime. There are two facts then which suggest that the nickel in [Ni(DMG)2 J is not oxidized in the reaction of this complex with bromine. The first is that palladium, which shows a fairly stable +4 oxidation state, does not give a material containing palladium(IV) in this system, but instead loses ligand which appears to be oxidized. The second fact to consider is that dimethylglyoxime ap pears to be attacked relatively easily by bromine. In view of these facts the existence of a higher oxidation 113 state for nickel in this system becomes quite question able. On treatment of [Ni(DMG)2 ] with bromine at 60° C. in chloroform over a 24 hour period a green product is obtained which, on analysis, appears to be a 1:1 mixture of [Ni(HDMG)Br2 ] and [Ni(HDMG)2Br2 ]. Comparison of the infrared absorption spectrum of the mixture (Figure 21) with that of the proposed constituents (Figures 21 and 23) supports such a formulation. (Since the infrared absorpticn spectrum of [Ni(HDMG)Br2 ] was not available for comparison, that of the very similar complex, Ni(HDMG)C12 *H20 was used.) Neither of these compounds exhibit any appreciable solu bility in chloroform; consequently, the compounds precipi tate as formed. If it is assumed that the first step in the reaction proceeds according to the equation [Ni(DMG)2 ] + 2Br2 — » [Ni (DMG-H) ] + L + 4HBr and then that the second step proceeds according to [Ni(DMG-H)] + 2 H B r — y [Ni(HDMG)Br2 ] and the third step is [Ni(DMG)2 ] + 2 HBr — y [Ni(HDMG)2Br2 ], it is immediately obvious that a 1:1 mixture of [Ni(HDMG)Br2] 114 and [Ni(HDMG)2Br2 ] should be formed. The species L which Is proposed in the first equation is the oxidized form of dimethylglyoxime. It has not been formulated as containing bromine; this is consistent with the observations of earlier workers who found that the reaction proceeds in 68,69 the same manner regardless of the oxidizing agent used. This product, which may brominate subsequent to the re actions shown above, Is undoubtedly responsible for the strong odor In the reaction mixtures. It is probably also the origin of the deep red color observed. The above proposed reactions may not occur in this system; it Is believed, however, that this is a plausible explanation for the observed reactions. These postulates, of course, are contrary to the large volume of literature in which the claim appears that the central metal atom in [Ni(DMG)2 ] undergoes oxidation. The solvent used In this work is different from that employed by other workers; it is suggested that this does not necessarily alter the course of the reaction. The choice of chloroform as the solvent greatly simplifies the system since the reactants are soluble and the nickel-containing products separate smoothly. It must be reemphasized that the observed reactions of bromine with [Pt(DMG)2] and [Pd(DMG)2 ] lend excellent support to the conclusion that nickel remains in the +2 115 oxidation state. [Pt(DMG)g] is a model for smooth oxidation in this system. It has been shown (above) that the complex [ Pt-^(DMG)2Br2 ] is formed in this system. Palladium, however, does not form a stable species of this type but instead loses ligand, which is oxidized, and forms [Pd(HDMG)Br2 l. Consequently, one would not expect nickel to exhibit an oxidation state greater than two in this system. When oxidation occurs it must be the ligand which is oxidized. III. SUMMARY Studies are reported in this dissertation which embody the preparation of the nickel(II), palladium(Tl), and platinum(ll) complexes of 2-pyridinaldoxime, their characterization, their reactions with organic reagents containing active halogen, and their reactions with bromine. Also included is the reaction of [Pt(DMG)2 ] with acetyl chloride, and the bromine oxidations of [Pt(DMG)2 ], [PdCDMGjg], and [Nl(DMG)2 ] which have been studied in an effort to achieve a better understanding of the contro versial [Ni(DMG)2] -bromine reaction. The composition of the compounds which have been prepared and of their reaction products has been verified by analysis whenever possible. The infrared absorption spectra have been recorded and, for the complexes of HPOX, several assign ments made. The magnetic moments and the conductivities have been determined for the nickel complexes of HPOX. 2-Pyridinaldoxime forms several different types of compounds with nickel(il) which differ from each other in ligand to metal ratio and in the total number of ligand protons which have been removed. These types are exemplified by [Ni(HPOX)3 ]I2, [Ni(HP0X)2Cl2], [Ni(POX) (HPOX)]I, and [Ni(POX)2], Among the compounds which were 116 117 prepared are found some which display properties that are quite unusual in view of what Is observed among nickel(ll) complexes with similar ligands, I.e., 2,2 *- blpyridyl, dimethylglyoxime, and 2 -methyl-2 -amino- - 3-butanone oxime. The most striking difference is to be found in [Ni(P0X)2 ], which should be similar In many respects to [Ni(DMG)2 ], The former is not precipitated from aqueous solution as are most oxime complexes of this type but, instead, it is quite soluble in water. Further more, this compound is strongly paramagnetic, which indi cates the existence of a nonplanar structure. A study of the temperature dependence of the magnetic susceptibility of this compound indicates that the susceptibility does indeed follow a Curie-Welss temperature dependence; it was found, however, that the Weiss constant 0 has the un usually large value of 226.3°. The magnetic moment, calcu lated using this value for 0, is 3.56 Bohr Magnetons. This compound could be a polymeric octehedral species (using oxime oxygens as additional donor groups) or it could display the unfavored tetrahedral configuration. A second unusual species appears in [Ni(POX)(HPOX)]I. This complex is also paramagnetic with an observed magnetic moment of 3.01 Bohr Magnetons. It is proposed that this compound is octahedral with donation from the oxime oxygens (as suggested above for [Ni(P0X)2 ]) or with sharing of iodides in the solid. 118 A third unusual feature is observed in the com plexes [Ni(HP0X)2 (Ac)2 ] and [Ni(POX)(HPOX)(Ac)(H20)]. The infrared absorption spectra of these compounds show carbonyl peaks which are of unusually high frequency (1760 and 1772 cm-1 respectively) and which are unusually broad. This high value suggests the COO-Ni link to be very co valent . Two palladium complexes have been reported in the preparative section of this dissertation; these are [Pd(POX)(HPOX)]Cl and [Pd(POX)2 3. The [Pd(HP0X)2 ]++ ion has been shown, by titration, to be a strong, dibasic acid. [Pd(POX)(HPOX)]C1 is precipitated from acidic so lution undoubtedly because of a favorable lattice energy. The only platinum complex isolated in pure form is [Pt(P0X)2 ]. It is very similar in its properties to the corresponding palladium complex, [Pd(POX)2 3. In this dissertation are reported the first re actions in which complexes containing an oxime ligand are acylated without complete removal of the oxime ester from the coordination sphere. Acetyl chloride readily reacts with [Pd(P0X)2 ] and [Pt(P0X)2] to form the acylated com plexes, [Pd(POX-COCH3 )Cl2 3 and [Pt(P0X-C0CH3 )2 ]C12 . Re action with the nickel complex, [Ni(POX)2 3, results in decomposition. The acylated platinum and palladium com plexes enjoy a fair degree of stability; on hydrolysis in 119 base the palladium compound forms a new complex, [Pd(P0X)Clj2 . The Infrared absorption spectra of the acylated compounds have been recorded; they are unusual In that the carbonyl band appears at a relatively high frequency, 1790 and 1780 cm~^ for the palladium and platinum com plexes respectively. Benzoyl chloride and benzyl bromide have been reacted with [Pd(P0X)2 ] to form compounds which have not been formulated. The infrared absorption spectrum of the product from the benzoyl chloride reaction shows a strong carbonyl peak at 1756 cm“^, which indicates success in the ester formation. As an extension of the work of Jicha and Busch,^ [Pt(DMG)2] has been reacted with acetyl chloride. The product has been found to be the same type of complex as that formed in the nickel and palladium systems, [Pt(HDM0)Cl2 ]. In the reaction with bromine, both [Pd(P0X)2 ] and [Pt(P0X)2] form complexes in which the metal atom exhibits an oxidation state of +4, [Pd(POX)2Br2] and [Pt(POXjgBrg]. The palladium(lV) complex is less stable than the corres ponding platinum(iv) species and under the appropriate conditions attack on the ligand begins; this yields 120 products which have not been formulated. Bromine causes the nickel complex, [Ni(POX)23 to decompose. The reaction of bromine with chloroform solutions of [Pt(DMG)2 3, [Pd(DMG)2 3, and [Ni(DMG)g] has also been studied. [Pt(DMG)2] is a model for oxidation in this system, the reaction proceeding smoothly to form [Pt(DMG)2Br2]. Bromine oxidation removes ligand from the palladium complex, how ever, to form [Pd(HDMG)Br2 ] and not the palladium(TV) species. In the reaction of the nickel complex, [Ni(DMG)2], a mixture of [Ni(HDMG)Br2 3 and [Ni(HDMG)2Br2 3 is formed and dimethylglyoxime is oxidized. The obser vation that palladium remains in the +2 state, and the mixture which is obtained from [Ni(DMG)2 ] in this system, lead to the conclusion that ligand is oxidized, and not nickel, on reaction of this complex with bromine. APPENDIXES APPENDIX I Magnetic Susceptibility Measurements Magnetic susceptibilities were determined by ihe Gouy method using an Ainsworth semimicro balance, capable of being read to 0.01 mg. Weighings were recorded to the fourth place only, however, because of the difficulties encountered in reproducing the fifth decimal place when a sample is suspended below the pan. The electromagnet was operated at a current of 8 amperes, and the apparatus was standardized using ferrous ammonium sulfate 6-hydrate 20 and water. Stoufer was consulted with regard to the characteristic peculiarities of the apparatus. Values for the molar susceptibilities of the standards were ob tained from Selwood;76 these values are T + 1 and A constant, which is dependent on characteristics of the apparatus used, i.e., gap between pole pieces, 122 123 field strength, position of sample tube, etc., was 20 calculated using the equation _ ^FAS^FAS PAS A W PAS where 9jpas is ol)Serve<3 density of the ferrous ammonium sulfate 6 -hydrate standard as it was packed in the sample tube, and AUf represents the difference in weight of the sample in and out of the magnetic field. The gram susceptibility is calculated using the equation ' V _ 'i/ x ^ ^ s a m p l e / '*gram “ '^standard sample using the value forXpAS foi> Paramagnetic compounds, and for ^H 2° for those which are diamagnetic. Occasionally the linkage suspending the tube was changed; this necessitated a restandardization of the equipment. For this reason the susceptibilities reported in Table 7 were calculated using several different values for^iA S . Prom the gram susceptibility one calculates the molar susceptibility by the equation ^ ^gram where M is the molecular weight calculated on the suppo sition that the compound is a monomer containing one 124 metal atom. The atomic susceptibility is calculated from the equation v where Is the molar susceptibility of the ligands and anions, and 11 is the number of each present per formula unit. Pascal's constants were used to calculate the molar susceptibilities for pyridine and acetate; values of the molar susceptibility were obtained from Selwood^ for the iodide and chloride ions, and this quantity was determined experimentally for HPOX. The data and calcu lated values for the magnetic susceptibilities and the magnetic moments of the nickel(IT) complexes of 2-pyri- dinaldoxime are given in Table 7. The data for the standardization of the apparatus are given in Table 8 . r TABLE 7 MAGNETIC SUSCEPTIBILITIES OP NICKEL(il) COMPLEXES OP 2-PYRIDINALDOXIME Compound (p(g./ml.) /K*r(eorrected ]^x 10^ TfK.) "^eff. for tube) M 106 ^NiX 1 0 6 (grams) HPOX 0.4823 -0.0013 168.7 -56.3 - 298 - [Ni(HP0X)3 ]l2 *2H20 0.7812 0.0230 179.6 3774.9 4070.9 298 3.12 11 [ni(hpox)2ci2 ] 0.8066 0.0481 4004.2 4163.5 298 3.16 [Ni(HP0X)2Ac2 ] 0.6543 0.0348 173.3 3841.9 4011.9 302 3.12 [NI(POX)(HPOX)(Ac)(H20)] 0.6826 0.0371 179.1 3688.1 4088.4 290 3.08 ft [NI(p o x )(h p o x )(py)2 ]i 0.5160 O.OI89 3851.3 4096.1 294 3.18 ft [Ni(POX)(HPOX)]I 0.4941 0.0227 3528.9 3692.1 293 3.01 H [Ni(P0X)2 (py)2] 0.6737 0.0265 323^.5 3428.7 292 2.83 125 TABLE 8 STANDARDIZATION OP MAGNETIC SUSCEPTIBILITY APPARATUS Standard p(g./ml.) AUT(corrected) T(°K) ^ x 106 (grams) Water 0.9957 -0.00425 300 168.7 Ferrous Ammonium Sulfate 6-Hydrate 1.1460 0.2030 298 179.6 ft 1.0569 0.1905 303 173.3 It 1.0063 0.1833 290 179.1 126 APPENDIX II Temperature Dependence of the Magnetic Susceptibility of [Ni(P0X)2 ] For the study of the temperature dependence of the magnetic susceptibility of [Ni(P0X)2 ] this compound was prepared and the sample tube loaded in a dry box as described in the experimental section, Part I of this dissertation. The cryostat described by Stoufer20 was used. Low temperature measurements were made using DuPont Freon 22 as coolant, the temperature being calcu lated from the vapor pressure-temperature data obtained 77 by Nielson. The thermostatting jacket of the cryostat was packed with ice for the measurement at 273°K., chloroform vapor was boiled through the jacket for the measurement at 333°K., and steam was used to maintain the temperature at 372°K. On the latter measurements a thermometer was lowered into the sample compartment before the determination of A W in order to establish the attainment of thermal equilibrium. 127 TABLE 9 TEMPERATURE DEPENDENCE OP THE MAGNETIC SUSCEPTIBILITY OP [Ni(P0X)2] ^ F A S = 179.1 x 10-6 ^sample = °*5078 g./ml. T (°K) a w (corrected) 'X * 106 1/yt eff *^eff (erams) n n i Ni _____(0 = .0°) (G = 226.3°) 183 0.0353 3860.4 259.0 2.38 3.55 232.1 0.0322 3531.3 283.2 2.57 3.60 273.2 0.0277 3053.5 327.5 2.60 3.50 295.3 0.0273 3011.0 332.1 2.68 3.55 298.2 0.0275 3032.2 329.9 2.70 3.57 333 0.0257 2841.1 352.0 2.76 3.57 372.2 0.0239 2650.0 377.4 2.82 3.56 128 APPENDIX III Infrared Absorption Spectra of the Nickel(il), Palladium (il), Platinum(ll), and Platinum(lV) Complexes of Dimethylglyoxime As mentioned above Infrared absorption spectroscopy was used as a control procedure in Section II of this dissertation. In Table 10 are listed the absorption peaks which appear in the infrared spectra of the nickel(il), palladium(ll), and platinum(ll) and -(IV) complexes of dimethylglyoxime which were studied. The infrared absorption spectra of these compounds are recorded in Figures 19 to 2 3 . 129 TABLE 10 INFRARED ABSORPTION SPECTRA OF NICKEL, PALLADIUM, AND PLATINUM COMPLEXES OF DIMETHYLGLYOXIME Frequencies in cm"■1 Pd(DMG)2 Pt(DMG)2 Pt(DMG)2Br2 Ni(HDMG)Cl2 *H20 Pd(HDMG)Br2 Pt(HDMG)Cl2 Ni(HDMG]^Br2 3410 s 3390 si 3430 s 3355 s-vb 3400 s 3425 m 3425 s 3220 mj 3290 s 3305 s-sp 3000 w 3200 s 3240 s 3120 s 2928 w 2928 ra 2928 w 1722 w 1707 w_ 1689 shh| 1676 sh 1657 s hJ 1658 w 1640 sh 1641 m 1645 m-sp 1649 m 1623 w-b 1628 m 1629 w-b 1629 sh 1630 sh _ 1630 w 1625 m 1617 s :1 1608 sh 1603 sh ~ 1600 m-SF 1598 s-sp 1591 sh 1579 sh 1583 sh _ 1564 sh 1565 s' 1565 sh 1563 W 1547 s-t 1547 m 1550 sh 1552 w 1539 sh 1545 w 1532 s 1531 w 1530 w 1529 1526 sh 1511 m 1515 sh 1515 w 1514 w 1503 sh M (JO 1497 w 1495 sh 1494 sh 1 O 1488 sh TABLE 10 (Contd.) Pd(DMG)2 Pt(DMG)2 Pt(DMG)2Bi>2 Ni(HDMG)Cl2 *H20 Pd(HDMG)Br2 Pt(HDMG)Cl2 Nl(HDMG)gB^ 1479 shj 1478 sh 1481 sh 1473 sh 1472 sh 1464 sh 1464 sh 1463 sh 1461 sh _ 1455 sh 1456 sh 1441 w-b 1445 m-b 1445 m-spl 1443 sh 1446 sh 1444 sh 1440 m 1443 sh 1 1426 s 1425 sh 1426 sh 1414 sh 1405 s 1395 vs-b 1413 vs 1408 s _ —* 1378 sh _ 1398 sh m 1387 m-spl 1376 s 1370 vs 1372 s= m 1383 sh sh -1 1364 sh 1356 sh 1357 s 1349 sh m 1340 w-b 1337 sh _ 1344 sh 1328 m 1325 sh ^ 1326 s 1339 s-sp 1316 m 1306 sh 1292 s _ 1282 sh 1256 s ' s 1277 s-sp - sh 1235 sh sh 1242 w 1238 m — 1216 S-Sp 1182 m-sp 1207 s-sp 1207 sh 1190 sh — 1179 w sh 1156 m-b 1143 sh m-b m-b U) 1132 1132 M TABLE 10 (Contd.) Pd(DMG)2 Pt(DMG),2 Pt(DMG)2Br2 Ni(HDMG)C12 .H20 Pd(HDMG)Br2 Pt(HDMG)Cl2 Ni(HDMG) 1109 sh 1102 sh 1102 shl 1100 sh — 1096 sh 1092 s 1088 m 1089 s 1093 s 1097 m 1084 sh 1074 sh 1079 sh 1078 sh 1079 sh — 1058 s-vb 1072 s 1076 s 1056 s 1063 sh_ 1057 sh 1052 sh IO38 w-b 1044 sh 1041 sh 1018 m — 1016 m 1010 m _ 1013 m 1007 m 1008 m 987 m 993 m~ 995 m 982 m 973 sh 948 s-sp 966 m 946 m 920 m-vb 927 w 906 rat 877 vw-b 906 w 827 shl 836 w 825 m J 817 sh 815 sh 809 s 806 m 742 s 741 s 748 s 717 sh 709 m 702 s 714 vs 719 s 703 s 712 sh_ w 667 w 668 m 667 m 668 m M s = strong, m - medium, w = weak, b = broad, sh = shoulder, sp = sharp, v = very. CO ro % TRANSMISSION % TRANSMISSION ioo(- 20 80 60 r O O 0 4 60 20 0 8 3000 0 0 0 4 L J I l i i l I I I 2000 2000 I L I J Infrared Absorption Spectrum of [Pd (DMG)j] [Pd of Spectrum Absorption Infrared 1500 1500 nrrd bopin pcrm f [PttDMGlj] of Spectrum Absorption Infrared RQEC (m'1) (cm FREQUENCY RQEC (cm") " m c ( FREQUENCY l 1000 1000 L. J x 900 900 x x i 800 800 _ 700 700 I- X LO 00 M Infrared Absorption Spectrum of [Pt(DMG)z Brz] ol__ I— !----- 1------1__I__ I__ I___1___ !___ I I_____ I______I______I I I_____ I______I______I______I__ 4 0 0 0 3000 2000 1500 1000 900 800 700 FREQUENCY (cm*1) to M F* n> n c ro % TRANSMISSION loop - 0 8 20 - 0 4 - 0 6 4000 00 3000 4000 _| ____ 3000 __L_ | ___ L 2000 2000 I L 1 I J I L I J nrrd bopin pcrm f [NilHDMGJ^rz] of Spectrum Absorption Infrared 1500 1500 nrrd bopin pcrm f CHCI of Spectrum Absorption Infrared f ecin f NfMt] n Brg and [NifDMGte] of Reaction of RQEC ( ' m (c FREQUENCY RQEC (m'1) (cm FREQUENCY 1000 _L. 1000 -J ____ 3 1 Insoluble Product Product Insoluble ____ 900 900 I ______L_ 800 800 700 700 135 8 o z I- tr z in 2 < % TRANSMISSION - 0 0 1 0 8 60 - 0 4 20 DOr 80 0 6 0 4 20 3000 0 0 0 4 3000 0 0 0 4 2000 2000 1500 1500 Infrared Absorption Spectrum of [Pt( HDMGICI^ [Pt( of Spectrum Absorption Infrared RQEC (cm"1) FREQUENCY nrrd bopin pcrm f [Pd(HDMG)Br2] of Spectrum Absorption Infrared RQEC 1cm FREQUENCY 1000 1000 900 0 800 900 800 700 700 % % TRANSMISSION 100 0 8 - 0 4 - 0 6 0 2 - 0 0 0 3 0 0 0 4 2000 nrrd bopin pcrm o N (D G)Cl2■HgO (HDM Ni of Spectrum Absorption Infrared 1500 RQEC fm’1) fcm.’ FREQUENCY Figure 23 Figure 00800 1000 900 u> •^3 H BIBLIOGRAPHY BIBLIOGRAPHY 1. 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In August of that year I enlisted In the United States Army for a period of three years, during which I served in several locations in the United States and Korea. On completion of ray military service in 1952, I entered The Ohio State University which granted me the Bachelor of Science degree in 1956. Immediately thereafter I entered The Graduate School of the same institution and in 1959 I completed the requirements for the degree Doctor of Philosophy under the direction of Dr. Daryle H. Busch, Professor of Inorganic Chemistry. 145