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University of the Pacific Theses and Dissertations Graduate School

1964

A study of the platinum (II), palladium (II), and rhodium (III) chelates of aspartic and glutamic acid

Cecilia Elizabeth Luschak University of the Pacific

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Recommended Citation Luschak, Cecilia Elizabeth. (1964). A study of the platinum (II), palladium (II), and rhodium (III) chelates of aspartic and glutamic acid. University of the Pacific, Thesis. https://scholarlycommons.pacific.edu/ uop_etds/1559

This Thesis is brought to you for free and open access by the Graduate School at Scholarly Commons. It has been accepted for inclusion in University of the Pacific Theses and Dissertations by an authorized administrator of Scholarly Commons. For more information, please contact [email protected]. A s TunY oF THE PLAT.tNu~ u'i). -PALLADi uM tn> •

.AND RHODIUM (Ill) CHELATES OF

ASPARTIC AND GLUTAMIC ACID

A Thes is

P 1·esented to

the Faculty of the Gr aduate School

Univer s ity of the Pacific

In Partial F ulfillment

of the Requirements for the Degree

Master of Science

by

Cecilia Elizabetn L uschak

J anuary 1964 This dissertation is approved for recommendation to the Graduate Council.

Department Chairman or Dean:

Dissertation Committee:

, Chairman

Dated ~ TABLE OF CONTENTS

CHAPTER PAGE

I. INTRODUCTION . . . . 1

II. THEORY •••• 3

1. Chel a t ing Tendencies of Aspartic a nd

Glutamic Ac id ...... 3

2. The Coordina tion of Palladium , P la tin um ,

and Rho di um . • • • . . . . 5

3. P l a tinum and P a lladium 6

A. The Val enc e B ond Method ...... 6 B. The Mol e cul ar O r bita l Approac h . . 7

C. The Crysta l F iel d Theo ry •• 7

D. The Val ence B ond Theory a nd

Rhodi um (III) 11

E . The Mol e c ul a r Orbital Theory and

Rho dium (III) . . . 12

F. The Crys ta l Fiel d Theory a nd

Rhodium (III) 12

4. L igan d F iel d Theo ry • • • • 13

5. Coval e ncy • • • • • • • • • • ...... 14 6. C r ys ta l F iel d Spectra of Rhodi um (III) • . . 15 iii

CHAPTER PAGE

"1 . Charge Transfer Spectra ••••• . . . . . 16

8. pH Dependence of the Reactions 16

9. The Preparat ion of Potassium

Tetrachl oroplatinate • • . . 17

III. EXPERIMENTAL • . • • • • • • • • • • • 19

1. Synthesis of the Chelates • • •• . . . . . 19

A. Bisaspartatopl atinum (II) 19 B. .B1sglutamatoplatinum (II) ••• . . . . . 21

C . Biaglutamatopalladium (II) •• • 22

D. Bisaspartatopalladium (It) • . . . 24

2. Stereochemistry of the P latinum (II) and

+ - P alladium--(11) Chelati)s . . -.-.~ . •

3. Pol ymeriz;a.tlon •••••••••••• 27

4. Synthesis of Bisglutama torhodium (III) and

Bis aspa.rtatorhodium (III) 28

5. Stereochemistry of the Rhodium (Ill) Chel ates • 30

IV. SPECTRA ••••••• ...... 32 1. E xperimental ...... 33

2. Infrared Spech·a . • • • • • • • • • • 33

V. SUMMARY ••••••••• ...... 39

B IBLIOGRAPHY • • • • • • • • • • • • • • • • • • • • • • 4 1

APPENDI X . . • . • ...... • . . • . • • . . . . 44 L IST OF TABLES

T ABLE P AGE

1 Infrared Spectra Assignments for Glutamic

and Aspar tic Acid . • • • • • • • • • • • • • • . 36

11 Absorbance Obtained in the Infrared Spectra

of Aspartic Acid • • • • • • • • . • • • • • 37

Ill Abso1•bance Obta ined in tl1e Infr ared Spect ra

of Glutamic Acid • • • • • . • • • . • • • • 3 7 LIST OF F IGURES

F IGURE PAGE

1 Bonding Orbital s of Palladium and P l atinum . 6

2 Splitting of the d - Orbital s in Squar e-planar

Compl exes of Platinum (II) and Palladium (II). . 8

3 Bisglutamatopalladium (II) . . • • • • • • . • 23

4 General Structure for the Palladium (II) a1td

P l a tinum (11) Chel ate s of Aspartic and

Glutamic Acids • • • • . . • • • 27

5 General Struc ture for the Dimer 28

6 P ossi bl e Structures fo r the Rhodium (III)

Chel a.tea • • • • . • • • • . • • • 30

7 ·tnfrare<.l Spectra o1Aspartic Acid . " . . 45 8 Infrared Spectra of Glutamic Acid ...... • 46 9 Infrared Spect ra. of Bisaspar tatopl atinum (II) • • • 47

10 Infrared Spectra of Bisglutamatopl atinum (II) • 48

11 Inf r ared Spectra o( Bisglutamatopalladium (U) ••• 49

12 Infrared Spectra of Bisaspartatopa.lladium (II)

fr om Method I • • • • • • • • • • • • • • • • • • 50

13 Infrared Spectra of Bisaspa1·tatopalladium (II)

from Method 11 • • • • . • • • • . • • • • • • • • 51

14 Ul traviolet Spectra of Bieglutamatopalladium (II) .. 5l

15 Ultr aviolet Spe,~tra of Bioaapartatop3.1ladium (II) •. 52 ACKNO WLEDGMENTS

The writer wishes to express her oincere t hanks to

Dr. Hers c h(~ l Frye, who directed the r esearch and acted as

Chairman of the Thesis Committee. She is al s o especially grateful to Dr. Emerson G. Cobb and Dr. Milton E • .F'ulle1· for their inspiration, encouragement, and guidanc e during the course of study. CHAPTER I

INTRODUCTION

It is fairly well known tha t alpha-amino dicarboxylic a cids combine quite readily with basic metal ions s uch as t he a lkaline earths. The lite r a ture indicates that considerabl e s tudy has been done in this area (Lumb and Martell, 1953). F urther s tudies have shown tha t ther e is also considerable a ffinity fol· the tra ns ition el ements and a good number of these have been investigated (Nyberg,

Cefola atld Sabine, 1959).

The nature of the problem includes the synt hesis and c ha1·a cterization of six platinum metal chelates of two alpha - amino dicarboxylic a cids, namely aspartic and glutamic a cids. The metal ions upon which the investigation is focused are platinum (II), palladium (II), a nd rhodium (III). Sever al of these are reported as having been prepared (Volshtein and Anokhova, 1959; Spacu and

Sc her zer, 1962). The series is incompl e te, however, and little study has been done correl a ting the stabilities a nd tre nds of the compl exes as a function of the metal ion and carbon chain l e ngth of the ligand acid m olecule . Hence, t he ultimate a im of the investigation is to s tudy the tendence of c hel a tion as the ca r bon c hain l engt h of the alpha- amino dicarboxylic a cid increases and also to study the stability of the 2

chelates as the central metal ion is varied. Because there are numerous problems involved here, the investigation extends

somewhat beyond the scope of a Master's research. Therefore the

investigation is limited 011ly to aspartic and glutamic acid.

The methods of synthesis for the palladium, platinum, and

rhodium chelatea oi aapa1·tic and glutamic acids were studied and

outlined. After synthesis, the means which were employed for

characterization included elemental analysis, molecular weight

determination, and infrared and ultraviolet spectra. CHAPTER II

THEORY

1. Cb.elating Tendencies of Glutamic and Aspa1·tic Aci~

Both aspartic and glutam ic acid have three functional g roups which could feasibly combine with metal a toms: two c ar boxylic a cid

groups and an amino g roup. If this is actually the case. they would

be considered tridentates. Ste ric considerations indicate that this is

quite unlikely, however. The lite1·ature (Volehte in and Anokhova,

1959• Spacu and Sche rzer, 1962) also indicates that these alpha~

amino dicarboxylic acids appear as bidentates, forming inner

complexes when com bining with metals of the second and third

transition series.

~ence , it is "13xpected that-aspartic-and glutamic acid behave

as bidentates in inner complexes of palladium (11) and platimtm (II).

F urthermore, the bonds between the metal ion and ligand would m ost

likely occur betwe en the metal ion and amino group, and between the

metal ion and alpha ... carboxyl group. As a r esult. a five member ed

r ing would be formed. This ring may be closed by t he formation of

coval ent linkages or coordinate bonds , or by the combination of the

two (Gilreath, 1958). The coval ent bonding is produced by the

r epl acement of a proton in the acidic carhoxyl group on the aspartic

and glutamic acids. 'I' he COOrdinate linkagt.S- uwithOtlt the 4 replacement of hydrogen--are formed by the donation of an electrotl

pair f1•om the amino group. This is shown by:

0 II C - 0 ~

c II 0

In case t here is bond formation invol ving the amino group and

the beta-carboxyl group, a seven membered ring would arise. This

seems leas likely on stability grounds. In general, chelates fo~ming

five ot· six mexnbered rings are the moat staale; from this it follows

that the beta-carboxyl group does not participate in chelate formation,

and one would expect the resulting inner chelate to have acid

character. It is perhaps worthwhile noting that this allows for the

possibility of salt formation with the beta - cal.~ boxyl group.

In studying tbe chelating tendencies of aspartic and glutamic

acids, Lumb and Martell ( 19 53) found that the a s par tate ion has a

higher affinity for the less basic metal ions, while ghttamate ion is

more effective in complexing the more basic m etal ions. They

conclude that for most divalent m etal ions, binding with aspartate

will be greater th.an with glutarnate. 5

The participation of the beta- carboxyl g roup in binding the metal ion is also ruled out by them . E ven thougb the additional carboxylate ion is probably not involved in the metal-chelate bonds, it has an indirect influe nce on the s tability of tl1e chelate ring (l.umb and Martell, 1953). The gene1·ally greater stability of the aspartate chelateB indicates that t he inductive effect of the negative beta­ carboxyl group leuds s tability to the a tructure by increasing the basicity of the donor g roups towards the metal ion. In the analogous glutamate structure thio inductive effect would be considerably weaker.

2. The Coordination of P alladiutn, P l a tinum, <-;:,!~.~~r.E.

After due considera tion one can predict the coordination number of palladium (II) and pl atilmm (II) to be four, and rhodiltm (III) to be six. This indicates that theoretically, we can have two alpha- amino dicarboxylic acid m olecules chelated with platinum (II) and palladium (11) a nd two or three molecules with rhodium (III).

It is well at this point to conside1· the various methods of

bonding applied to the coordination of t hese metals. The three methods include the valence bond technique, which conside1·a that the

bonding electrons belong only to the pair of linked a toms, the mol ecular orbital theory, and the crystal field--or ligand field-- 6 method. In reality all of these, particula rly the ligand field approach, have achieved considerable auccesa in explaining chelate co mpounds.

3. P latinum and P alladium

A. The Val e nce Bond Method:

In our case the valence bond method predicts two possibl e configu1·a tions··te trahedral and square-coplanar . E lements having no d- el ectrons of suitabl e energy availabl e use ap3 hybri d ization and must therefore be totrahed1·al in structure when chelating. If d- electrons a re available, then t he four coo1.•dinate chelate m a y be either te trahedr al or square coplanar. Since both palladium (II) and platinum (II) have d orbitals available, the dsp2 configuration, involving the h ybridization of the d ? , a , p and p atomi c X~~ 2 X y orbitals, would most likely occur, as shown below:

Palladium (II) .,

4s 4p 5s @ @@@ @@;® IQ Q Q ~ I 0 1... L L L

P l a tinum (II)

59 Sp 6s @ @@@ ®®®®IQ Q Q ~I 0 L L L L

F i gure 1. Bonding Orbital s of Palladium and P l a tinum 7

B. The Molecular Orbital Theory:

It is important to realize that it is not elwa.ys possible to predict which configu:ratiot"l will have the lowest ene1•gy for a given metal ion and ligand. from valence bond calculations. Henee, it is important to consider the molecular orbital approach. as well when attetnpting to ascertain the geometrical structure of a given chelate.

The molecular orbital method usee the same orbitals as the valence bond approach, but compound~ them witn the ligand orbitals to give m olecular orbitals. The orbital symmetl'ies are such that the d and s orbital s of palladium (II) and platinum (11) can X 2 uy 2 combine with the el ectrons from aspartic and glutamic a cids, but the Px and Py orbitals can only overlap with the bidentate along the x and- y- axio tGarl:mell and Fowl es, 196! ).

C. T~e Crystal Field Theo:t·y:

When approaching the probl em as an advocate of the ligand fiel d theory, one ia mainly interested in the influence of t he charge field created by the ligands on the d orbltal tl of the metal ion. The effectG are very dependent on the various geometries and the strengths of the individual ligands.

When considering the transition metal itself, the d orbital s are degenerate, but as soon as the ligands approach an electrostatic field arises which different iates the ir energies. The orbitala l ying 8 in the direction of the Uganda are raised in energy in comparison with those which lie below the ligands. (Day and Sel bin, 1962. )

The splitting of the d ot·bitala of the platinum (II) and palladium (II) central cations produced by a square.. planar arrangement of the ligand m olecules causes the d l evel to be X 2 • y 2 the l east s t able and much higher in energy than all the others. The dxy orbital has the next highest energy, since the ajees of its l obes all lie in the plane of the ligands. Since the ligand field influences the d and d orbitals to the same extent, they seem to become yz xz degenerate . It is difficult to determine, however, just how much their energies differ from the d z orbital. z

I I I I

/ d ------.. I ,. " xy ------}(~, ------,, ' d 2 \ \ z \ \ Free Metal \ \ Ion ' } d • d '------xy yz After approach of the Ligand

Figure 2. Splitting of the d Orbital s in Square·planat· Complexes of P t (II) a nd P d (II) 9

Basolo and Pearson (1958) describe the d 2 orbital as z having an ener.

may be justified on the grounds that the collar of charge in the xy

plane of the d 2 orbital gives a greater t•epula ion of the ligand field• z The principal factors which determine whethet• or not the

transition metal ion with a coordination number of four will form a

tetrahedral or square ... planar complex, are the ct•ystal field

s tabilization energies and the mutual repulsion between the ligands.

The latter will depend on the bulk of the ligand and its electro-

negativity. If the C. F . S. E . is to be the only critel'ion to be

considered; then all four coordinate complexes of palladium (II) and

platinum (II) will be square planar, except where the C. F . S. E. is

--ze1·o. 1Cartmel and7owles, fCf61 . ) lt is importantt however, to

take into account the mutual repulsions between the ligands, for this

repulsion is quite significant wb.en the ligands are bulky. This steric

factor will be particularly impor tant when the field is weal' and the

C. F . S. E . is small. The repulsion will be l ess important in

complexes formed by transition elements of the second and third

:rows, where the C. F . S. E . is larger .

I . Even tbough the s trength of the field will be mainly determined I by the nature of the ligand. the char ge density of the central metal

ion also plays an important role. If a weak field is produced, 10

el ect r ons are prom oted to the higher energy level before pairing

occurs , and if the fiel d is s t r ong there will be spin pairing. In effect

there is als o a competition between additional crystal field s tabilization

produced by spin-pairing and the operation of Hund' s r ule a, which

state that the most s table arrangement of electrons in atoms is t hat

which gives the maximum number of unpaired spins, according to

Cartmell and Fowl es (1961).

The C. F . S. E . and the diffe rences in energies for weak and

s trong fJ.elds for palladium (II) and platinum (II) ahow that the r e ia

no gain in orbital energy in a. strong fiel d. 'fhe ligand fiel d approach

shows that the square-planar arrangement can give r i se to either

diamagnetic or paramagnetic chelates, depending again on the

-strength of the ligand. W-ith a strong fiel d, we get spin pah·ing and

diamagnetism, a nd with a weak field, we get t he maximum number

of unpaired electrons and paramagnetism. Because of the larger

value of C. F . S. E. with palladium (II) and platinum (II), spin pairing

is likely to occur, and square- pl anar rather than te trahedral chela teo

tend to be formed with these ions. Hence the chelates of the heavier

metal s-- pla tinum and palladium .. - are most probably planar,

rega1•dless of the nature of the ligands, and these are furthermore j 1 al so spin-paired and diamagnetic. This has been shown to be the 11

case for seve1·al complexes of palladium and platinum by Owston and

The planar arrangement of bonds in dival ent platinum

compl exes is further confirmed by dipole moment measurements on

a number of complexes. Interestingly enough, th.e IZel'O • dipol e forms

must be trans-planar and the high dipole forms are almost certainly

cis- planar. With palladium complexes only the tl·ans form can

normally be isolated (Cartmell and Fowles, 1961).

D. The Valence Bond Theory and Rhodium,:

From the valence bond point of view, el ement s exhibiting a

coordination number of s ix m ust have d orbital s available to form

s ix bonds, because s and p orbitals can accommodate only four

unpaired electr ons. There are three conceivabl e configura tions,

pl ana1·, trigonal-prlsmatical, and octahedral, but the octahedral

should be the m ost s table (Cartmell a nd Fowles, 1961). Since

various experimental methods s uch as magnetic meaSl-\rements have

shown that the six bonds at•e al m ost invariabl y octahedrally arranged,

the s patial a r1•angement of the chelates is fairly certain.

According to the val ence bond method, the r hodium (III) ion j has six orbitals ava ilabl e, namel y the 3d z· , 4d , 5s , 5px , 1 z x>4-y·2 2 Py , and Pz • Suitabl e linear combinations of these are m ixed to

form s ix equivalent hybrid orbitals d 2ap3 ; these are directed 12 along the x, y, and z axes. Again, this type of hybridization indicates the formation of an inner complex. The ligand donates its el ectrons, gi ving maximum overlap for octahedt·al coo1•dination.

E . Mol ecular Orbital Theo1·y and Rhodium (III):

When the molecular orbital theo:t·y is applied to octahedral complexes, the el ect rons are considered to be in molecula1· orbitals which are no l onger l ocalized between the metal and any one ligand.

B y using the Linear Combination of Atomic 01·bitals tecbnique, one is abl e to compound twelve molecular orbitals·-six bonding and six antibon.ding .. -fr om the six atomic orbitals of the metal, and the six sigma orbitals of the ligands. The twelve el ectrons from the six ligands are placed in the six bonding molecular orbitals. This method ia extremely useful in making quantitative data a nd predicting absorption spech·a and magnetic properties.

!:.:__The Crystal l!.. ield Theory and !'hodium (Ill ):

With a central cation such as rhodium (III) with a coordination number of six, the ligands approach the metal ion along the x, y, and z axes, and the charges of the ligands will t•epel an electron to a greater extent if it is in a d 2 or d 2 orbital, 1•ather than in a Z X -y 2

or d orbital. This seems quite feasil>le since the yz fot·me1· point directly towards the approaching ligands. The d z. z 13

and d 2 z orbitals are al so used for obtaining bonding ot•bital s in X - y both the val ence bond and molecular o1•bital met hods. In terms of

energy l evel s, the original degeneracy is split into two parts fot•

octahed1·al c ompl exes. The d 2 and d l. assume a higher Z X -y 2 energy than they would have if they were not di rected towards the

ligands. The dxy , dxz , and dyz , on the other hand, assume a

lower

Other than providing electrostatic perturbation, the ligand ia

p1·actically ignored in crystal field theory. It is true the central ion

dominates the situation; however, consistent departures from the

crystal fiel d characteristics have been a ttr ibuted to the negl ect of

the nature of the ligand. Therefore instead of only the simpl e crystal

fie l d approximation, we-have the-appliC11tlon of the ligand field

approximation--a fusion of the mol ecular orbital theory and the

crystal field theory.

0 4. The Ligand .Fiel d Theory

Because of t he apparent inadequacy of the crystal fiel d

theory, the ligand field theory, a somewhat more accurate treatment,

must be introduced. Here the electr ons which are not concerned in

the transitions suppl y the perturbation potential and are then ignored, 1 but the symmetry of this potential decides the symmetry of the

molecul ar orbitals, which can be formed from the ligand and the 14 metal ion orbitals. The occupation of these mol ecul ar orbitals, which were in the crystal field model purely t ..?g and e g electrons localized on the central ion, allows a discussion of the opectra on a fully molecular basis.

5. Covale~C)!:

It is interesting to note that after a period of rejection of the concept of a covalent bond in coordination chemis try, it has become increasingly apparent that facts such a s dec1•eases in the free ion spin-orbit coupling pa:~;•ametc1'13 (Dunn, 1959) and s uggested reduced

II inte1·el ech·onic repulsion between d electrons (Jorgensen, 1957}, r equire cha r ge transfer from the ligands to the centl·al ion, or at l east some charge delocalizatlon. Hence we have the 1•ebirth of a covalent bond concept .

A series can be set up which will express the 11 covalent" tendencies of the ligands with. l.~ espect to bond formation. Schaffe r

II and Jorgensen ( 1958) devised the "neph.elauxetic series " a s such a measure. It has been shown that the interelectl·onic l'epulsive forces

between d el ectrons are decreased by complex form ation. The expansion may be cor1•elated with the extent to which covalent bond formation occurs. The positiOl'lS of the various metal ions in the nephelau.xetic series are difficlllt to define but in gene r al are:

dipositive tripositive te trapos itive ions < ions < ions 15

This would be expected purely f rom the viewpoint of pol arization forces causing large distortions of the ligand el ectronic structure.

The series is also dependent upon t he electronic conatitution of both central ion and ligand; for instance whether the metal and/ 01· the ligand has empty, partially filled. or fully filled t and eg 23 levels. The series could be quite useful aince it may enable one to

confirm or deny the presence of some complex species in solution merely from a knowledge of the spectra of similar complexes

(Lewis and Wilkins, 1960).

6. Crystal F ield S2<:_c£ra of Rhodium (II!L

Nearly all the applications of the crystal field theory to the absorption spectra of the complexes with partly filled d-shell have

concerned mainly the first transition group with d electron s .

II Jorgensen ( 1956) found that the energy differences in the 4d case are l arger than in the 3d case. Similar conclusions were drawn by

Orgel in 1955 from qualitative observations of the colors of the

pl atinum group complexes compared to cobalt (Ill).

The 1•egularly octahedral complexes of the d6 system of

rhodium (IU) was studied and its absorption spectra can be explained

as are the c1·ystal held bands also found for the cobalt (III) complexes.

How~ ·11 1. r . this by no means proves that the el ectrostatic m odel of the

cryatal field, acting on th, d - el ectron s, J.s a vet·y good approximation 16

for the actual states of the transition group complexes. The

octahedral complexes of the platinum metals often exhibit relatively

II strong absorption bands. (Jorgensen, 1956. )

' 7. f.harge Transfer Spectra

Examination of the ultraviolet and visibl e spectra of many of

the complexes of the second and third row transition elements shows

that the cha1•ge transfer bands swamp out any bands which might be

crystal field type. 1'he intensity of the charge t ransfe1· bands

indicates only whether a transition is electronically allowed or

forbidden and that the el ectron transfers from one center to the

other. It is immaterial whether the electron al'ises from the metal

orbits and transfers to the ligands, or vice ve1·aa. On the whole

this presents some complications in spectra inte1·pretation. Also

the complications of spin- orbit coupling are likely to be much greater

and this requires many of the theoretical approaches to be of the

Intermediate Domain type. These are often difficult to interpret

(Lewis and Wilkins, 1960).

8. i?H Dependence of the Reactions

It was shown by Craig, Du1· je1·, Glazer and Horning ( 1961 ),

1 by investigation of cobalt complexes of aspartic and glutam i c acid,

that the cl1elating capacity is greatly reduced in strongly acid 17 solutions, that is, below a pH of 3. 0 for aspartic acid, and below a pH of 4. 1 for glutamic acid. Above a pH of 6. 5 the metal hydroxide is formed; optimum conditions are at a pH of about 4. 8. For bivalent cations , the stability of the 1: l gl utamate complex is appreciably less than that of the 1 ~ 2 aspartate complex.

Since the chelating agents attack in the anion form, it is evident that chel ation is favored by a rela tively high pt-l ; on the othef hand, competition by hydroxyl ions fot· the coord ination positions about the metal ion may tllen become s erious . F or instance, inves tigations of the stability of iron (III) complexes with alpha·amino dica 1·boxylic acids have shown that at the highest practicable pH value·~4 . 7--stable 1: 1 complexes a re fo rmed (Perrin, 1958). In less aciEiie- solution,-separation of iron (III) hydroxide obscu~es the possible existence of higher complexes.

9. ~-h~ Preearation of Potassi~ Tetrachl o;,oplatinate (I!)

The problem of synthesizing potassium tetrachloroplatina te is encountered by a nyone occupied with the ~:Jtltdy of various plat inum chelates. Thia is the s tar ting material for many of the reactions.

The known procedure for preparing this substance involves reducing potassium chloroplatinate according to the reaction; 18

This vades according to the nature of the reducing agent employed.

A common procedure, widely used in practice, is the

Chugaev Procedure ( ! 929). This calls for the reduction of potassium tetrachloroplatinate by potassium oxala te in the presence of platinum black as a catalys t according to the reaction1

The difficulty with t his method ie the necessity for using platinum

bl ack as a cat alyst. The preparation of this material is unfortunately more compl ex than the chloropl atinate synthesis itself.. If the platinum black is stored, it loses ita activity and becomeo l ess eff-e-cttve-;.n reducing- the chloroplatinate. In addition, the activity~ of

the platinum black actually depends on the process of its preparation,

control of wh.ich may be very difficult.

In 19 52, Gildene1•s hel and Shag is ultanova proposed a better

method by which they use a new reducing agent requiring no catal yst.

This reducing agent io hydrazine s ulfate, N 2H6so4 , which reacts with chloroplatinate in the following manner:

This method is extremely successful in producing a high yield and

has also a short reaction tlme. CHAPT:t:R Ill

EXPERIMF.: NTAL

L S ynthesis of the Chelat es

A. Bisaspat•tato,el a tinum (I!)

The bisaspartatoplatinum (II) chelate was prepared according to the metb.od of Vol hte in and Anokhova ( 1959).

250 ml. HO 2 reflux ~ [ Pt (HAsp) l. J 20 hours

Four moles of aspartic acid, which was made available through

Matheson Company, Inc., were reacted with one mole of K P tClA ------2 ~ (supplied by the Fisher Scientific Company) in 250 m l . of water placed in a 500 ml. standard taper Florence flask. This was fitted with a reflux condenser, and the reactants were l'efluxed for a period of twenty hours, the time required for a comple ted reaction. During this period the solution changed slowly hom yellow to colodese, and after e vaporation of the solution to 100 m l. , a white solid was obtained. This solid was separated by filtration f1·om the hot solution, washed with hot water to rem ove any unr<~act ed aspartic acicl, and finally dried at room temperature under reduced pressure. 20

T he reaction described above res ults in the formation of a

m ixture of the cia ... a nd trans-isomeric chelc.teo. 'l'he trans-isomer

is chiefly p1·ecipitated in hot d ilute solutions and the cis-isomer

chiefly from cold concentrated solutions (Anokhova and Volshtein,

1959). Hence, it is most likely that the trans-isomer was prepared.

Anokhova a nd Volshtein (1 959) suggested a proc edure for

dete1•m ining the amount of cis-isomer in tne m ix ture1 however, this

was not attempted. The method involves the titra tio n of the

bisaspartatoplatinum (II) chelate with KOH to give K2 [ P t AspJ 2 ,

which could then be titrated with HCl and thiourea succesaively to

g ive [ Pt (thio) Cl The formation of this complex would show 4 2 J. the presence of the cis form.

Characte1•1zatien of t he- white product -was partially

a ccompliahed by carbon-hydrogen analysis . Analyses by the West

Coast Analytical Laporatory are as follows :

[ P t (HAsp} 2 J Theoretical Reported

1. Carbon 21. Oo/t 20. 62o/o

2. H ydrogen 2. 6 l o/~ 2. 53o/u

1 It was al so found that no melting o r decom position takes place unde r 300°C. The IR spect ra p resented l a ter in thi s thesis also aided in

characterization. 21

The presence of bisaspartatopl at inum (II) chelate is further substantiated by reaction of the white precipitate obtained above with concentrated HCI and oubsequent boiling for several minutes.

A yellow precipitate is obtained for which th.e r eaction iss

This yellow s ubstance is solubl e in water and ethanol but is insoluble in 6N hydrochloric acid and e ther .

B. Bisglutamatopla tinul'l!.JII)

T he inner bisgl utamatopl atinum (II) chel ate was s ynthesized with m uch grea.ter ease than the bisaapartatoplatinum (II) chelate.

The method, howeve r , was very s im ilar and bad been Sltggeste

Grinber g and Kata in 1955. 'l'he reaction invol ved is:

250 m l. H 0 2 reflux ) 3 hours

Four mol es of gl utam ic a cid, supplied by Eastman 01·ganic Chemicals and 1·ccrystallized from water, was reacted with one mole of

K2P tC14 in 250 m l. of water. The apparatus was s i m ilar to that described in s e ction A. Reaction wa s effected in three hours and was accompanied by a c olor change from yellow to colorless. A white 22 precipitate formed which was filtered from the hot solution, washed with hot water and dried under t•educed pressure at room temperature.

The carbon and hydrogen analysis obtained is as follows:

[ Pt(HGt) 2 J Theoretical Reported

1. Carbon 24. 65% 25. 150A

2. Hydrogen 3. 28% 3. 17%

Again no apparent melting or decomposition seemed to take place below 300°C.

C. Bisglutamatopalladium (II)

The bisglutamatopalladium (Il) chel ate was prepared according to the method proposed by Spacu and Shc1·zer in 1962.

The reaction is as follows :

A concentrated K PdCI solution was added to a glutamic acid 2 4 solution in a one to four mole ratio. The K P dC1 was obtained 2 4 £:rom the Chemicals Procurement Laboratories. The solution was diluted to a volume of 250 ml. and heated for a short time on a hot pl ate. The solution became yellow and was allowed to evaporate for four days at room temperature, after which time yellow crystals 23 were deposited at i:he bottom of the beaker.. These wer e removed by filtl·a tion and dried under t•educed pressure a t room temperatut·e.

The yellow crystals o btained in a pproximately 60% yield were slightly s oluble in cold water and very s olubl e in hot watet·.

Upon tl·eatment with 6 N HCl. they dissolved a t room temperature.

When this s olution wa.a evaporated. a darlt brown h ygroscopic mass

1•esulted.

According to Spacu and Shet•zer ( 1962) the yellow crystals obtained have the s tructure

OOC .::: CHCH 2COOH) 2 J H 2N

Ftgure 3. ~ lsglutama~opalladiunr(II)

and a re the inner pall adium glutamate chel a t e. E l emental carbon and hydt•oge n anal ysi s is as follows:

[ Pd(HGt) ] 2 Theor etical R eported

1. Carbon 30. 30% 30. 08o/u

2. H ydrogen 4.02o/o 4. 27%

Decomposition of th.e [ P d (HGt) crystal s takes place above 244°C. 2 J 24

D. B~sa.s~: tatoealladium q11

Two different procedures are employed in preparing the

bisaspartatopalladium (II} chelate. The first method of preparation is analogous to that of the bisglutamatopalladium (ll) chelate: fo ur mol es of aspartic acid were reacted with one m ole of K 2PdC14 in

250 ml . of water to give [ Pd (HAsp) 2].

Again, yellow crystals we re formed which were f\ltered and dried in vacuum at room t ernpet•ature; these we1· e found to have the following

carbon and hydrogen analysis:

[ Pd (H Asp) 2 ] Theoretical Reported

1. Carbon 25. 28o/l'

2.. Hydrogen 3. l4o/n 3. 46%

Apparent decomposition takes place above iW0°C.

The second method involves the 1·eaction:

Sodium aspartate was prepared by mixing aspartic acid with sodium

bydroxide in a 2: 1 mole ratio, in 500 m l . o£ wa ter. A 0. 0 1M 25 solution of palladium chlor ide, which was m ade available by the

K and K Laboratories, was prepared by d is sol ving the s olid in water, adding a small quantity of 1N HCl and heating gently until d issolution was complete. 100 m l. of the t•eoulting yellow 0. 01 M

PdC1 2 was reacted with 400 ml. of 0. 01 M sodium aspartate solution. This solution was divided into four portions a nd adjusted. to a pH of 3. O, 4. 0, 5. 0, and 6. 0 respectivel y with HCl. The solutions were then allowed to evaporate at room ~emperature . After three days yellow crystals were deposited in t he sol ution a t a pH of

5. 0, a nd after a week in t he solution a t pH = 4. 0. The s olutions at pH = 3. 0 a nd pH = 6. 0 produced no yiel d afte r the same dura tion of time.

The yellow crystals were filtered a nd--dried in-vacuo auoom tempe rature and tested for the compl ete removal of chl oride. This was effected by pt·e cipitating palladium oxide from the yellow crystals by boiling with concentra t ed sodium hydroxide. T he black precipitate resulting was removed by centrifuging, a nd silve1• nitrate was added to the supernatant. The supernatant remained cleat·, indicating that _..... 0 the fo:nnation of Asp J? d ""- had not occurred. The com position of Cl the yellow crystals was confirmed to be [ Pd (HAsp) 2] by carbon a nd hydrogen analysis. 26

[ Pd (tJAop)2J Theoretical Repo1·ted

1. Carbon 26. 0% 25.520/o

2. H yd1·oget1 3. 28% 3. 4.1o/o

The IR spech·um of this chelate was almost identical with that obtained from the product of the first m ethod of p1•eparation. Decomposition of the yellow crystals took place slightly above 200°C.

It was found, however, that the second method is m ore inconvenient and less efficient than the first, partly due to the mo1·e sensitive pH adjustment involved. As in the first procedure, a n excess of aspar tate ion above that indica ted by t he s toichiometry of the reaction needed to be added. --

2. Stereochemistrx; of the P latinum (II) and P alladium (II) Chelates

Palladium (II) and platinum (II) are d8 systemo, being tetracoordinate a nd usually for ming complexes of a oquare planar natu:re; thus atructu1·es arc expected for [ Pd (HAsp) .?J, [ P t ( HAsp)~ ,

[ Pd (HGt) 2] , [ P t (HGt) z] as follows: 27

0 II HOOC (HzC) c --0 NH --c n / 2.

~ 0 C (CH ) COOH c 2 II n 0

Figure 4. General S tl·ucture for the P alladium (II) and Pl atinum (II) Chel ates of Aspartic and Glutamic Acid .

M = Pd (II) or Pt (II)

1 (H Asp) n = 2

n = 2 (H 2G t)

'rhis s tructure is also indicated b y Vol shtein and Anokhova ( 1959),

Grinberg and Kate ( 1955), and Spacu and Shet·zer ( 1962).

3. P olymerizat io~

It is fairly well established that there are two ligand mol ecul es

associated with one m etal ion. A further considet·ation is necessary,

however . This is wb.ether or not the chelate exists as a monomer

or .. - poosibly- -as a dimer. F igure 5 illus t rates a possible

configuration fo r such a dimer .

J 28

COOH 0 0 (CH ) II 2 n II c - o NH - CH C - 0 NH C H(CH ) COOH 2 2 2 '\ / \. / n M M / '\ / "\ -OOC n (H C) CHzN 0 - C - CH H N 0 - C 2 2 II I II 0 (CH ) 2 0 I n COOH Figure 5. General Structure for the Dimer

A molecular weight detennina tion woul d decide this quite readily, l>ut unfortunatel y flever al difficulties were encountered here. The inability to find a suitable solvent which would dissolve the chelatcs to allow for a moleculu· weight determination by the Rast method, and the fact that the-compounds de con1pese ,-~ather than molt, are tha-principaLpro bl em s involved. Hence no conclusions can be d1·awn as to the polymerization of the chelatcs at this time.

4. Bisglutarnatorhodium (III) and Bisaspartatorhodiurn (III)

The synthesis of the two rhodium chel ates presented some difficulties. Anhydrous rhodium chloride is highly insoluble; thus

RhC13 ' 4H 20 , obtained from the Chemicals P rocurement Laboratories, was used. Thio compound dissolve s readily in water, forming a reddish brown solution. Apparently an equilibria exists

between the aquo ions and chloro ions (Cotton and Wilkinson, .1 961). 29

This is readily observed when one attempts to precipita te chloride ion with silver nitrate solution; essentially no silver chloride is precipitated.

RhC13 · 4H 20 and glutam ic acid were m ixed in a 1:4 mol e ratio in 250 ml. water and were refluxed for 40 hours. The initial reddish brown solution olowly turned a pale yellow du1~ing the course of reaction. A small quantity of grey residue, presumably RhO or

Rh o , remained. The s imilar procedure was employed in reacting 2 3 RhC1 ' 4H 0 and aspartic acid in a 1:4 mole ratio. The results 3 2 were similar to the glutamate reaction.

Both the remaining solutions were evaporated and a brown glassy resin.. like substance remained. The glutamate compound was recrystallized by di-ssolving it-in hot butanel-1 and slowly add-ing ethyl ether. A pale yellow flaky precipitate formed, which decomposed almost immediately upon exposure to air. Even under a nitrogen atmosphere, the yellow compound was too unstabl e to be analyeed spectroscopically or by other means.

The aspartate :resin.. like material was much l ess soluble in the higher alcohola. A mixture of ethanol and ethyl ethet· was used for recrystallization. The yellow precipitate which was obtained decomposed slowly in air and seemed relatively stable under a nitrogen atmosphere. This compound was dl'ied unde1· reduced 30

pressure at room temperature and was sent out for carbon and hydrogen analysis. The results are as follows:

1. Carbon 24. 16%

2. Hydrogen • 4. 42o/o

5. S t~eor.hemistry of the Rhodium (III) Chelatca

As mentioned earlier, rhodium (III) chelates in general

appear to have an octahed ral s tructure, but a question remains

whether two or three ligand mol ecules are asaociated with the central

metal ion. The following are possible structures of the rhodium

chelates in question:

+++

I II

0 II c ( CH ) __..- -.__ 0 0 2 n l -"/ ---c H~ - - I-1 R't•- - Y' -2 I Ill c - - 0 I NH2 II o o -- c II 0 --- Figure 6. Possibl e Structures for the Rhodium (III) Chelates 31

E ven though the first two structures appear oter ically feasible, they are ruled out on the basis of poor carbon and hydrogen analysis correlation. The deviation consider ably exceeds predicted expe1·imental error. The closest correlation is found with structure

III (Fie. 6). This structure is actually analogous to the one proposed by Diehl (1937) and by Chaberek and Martell ( 1952) for the free acid of cobalt aspartate. The theoretical carbon and hydrogen analysis calculated for this structure is as follows:

1. Carbon 26. 2%

2. Hydrogen 4. 42o/o

This does not compare too l\nfavorably with the reported values within a margin of experimental error. If this structure is correct, both the alpha- andoeta-carboxyl gl"OI.IpS are involved in chelate formation, causing a considerable strain on the ligand molecule .

This is perhaps the reason for the instability of the chel a te out of solution. CHAPTER IV

f)PECTRA

Use: of molecular spectra is a great aid in c haracte l'izing the chelates and studying their configurations. Molecules can absorb radiation by making a transition from one energy state to another of highe1· energy. A m olecular absorption spectrum ca.u be obtained by passing radiation of a. continuous spectrum, such as ultra .. violet, visible or inh-ared, through t he substance. The transitions may involve changes in electronic, vibrational and rotational energies.

The electrons in molecules may be in one of a number of possible energy states or l evel s . These energy l evels are of very different energies and tra nsitions from one levol l:o a n excited state of higher ene1•gy produce alJGorpfion in-the UV l'egion ot-th~sp~ ctrum .

The much smaller ene1•gy changea associa ted with the quantized vibrations of t he nuclei about equilibrium pooitions in the m olecule produce absorption in the nea1· infrared region of wavel engtns from approximatel y 1 to 2.5 m icrons. The energy associated witll the

1•otation of the molecule about its center of gravity is al s o quantized, but the quanta are very small, and absorption produc ed by changes in rotation appears in the fa:r infrared and t•adio m icrowave regions of very long wavelengths. 33

1. Experiment B:,l

Visi bl e and ultraveiole t spectra we r e run on the Bec k man DB

Spe ctrophotom e te r; infra1·ed s pectra were prepared on the P erkin­

E l mc r 13 7-13 d ual beam ina trumen t. In gene 1·al it was found tha t

neither the ligands--aspartic and glutamic a cid--nor the compl exes

a bsor bed in the visible r egion of the spectl·um . Also, there was no

appar ent abso1·bance in the UV r ange for glutamic and aspartic a cid.

The only c omplexes which showed any absorbance in this r a nge were

[ Pd (HGt)2J a nd [ Pd (HAsp)2J. A d e ta iled analysis of the UV

absorption spectr a of m ole c ules produced by changes in el e ctronic

energy, p1•esents many difficulties and in thi s case very little c an

a ctually be ascertained from them except that t he s pe ctra of the

palladium chela tes is s ufficiently d issim ilar from the ligands - --- themselves , to indica te that chelation has taken pl ace . Since t he

pl a tinum c hel a tes do not abso1·b a t all in the UV, no analog y can be

made concerning them. These a r e all included for inspec tion in

F igures I+ a nd 15 in the Appendix.

2. Infrared Spectra

E ve n t hough these chel a te compounds do not have

cha racte ristic absorption spectra in the UV r egion, they appear to

have very detailed spectra in the infrared reg ion. This ca n be

ext remel y useful as an identifying char a cterist ic. ]fortunatel y s tudies 34 have been made which have led to cataloging of the I R spectra of many compounds. Functional groups have been assigned

characteristic absorption bands and one is able to determine the

principal functional groups within the compound of interest and the1·eby

identify it. However, while IR spectra are ext1•emely useful in

identification, they are not always conclus ive evidence. In 1955,

Kogel and his co-workerG did considerable work on the IR spectra

of aspartic and glutamic acids; these spectl·a u·e useful in

characterizing the respective chelates, s ince the wavel engths a t

which the various functional groupe aboorb will vary depending on tl1e

structure of the chelate and any bonding which has taken place dur ing

chelate formation.

Of considerabl e-value in t-h e interp1.·etation of the-ionic state_o{

the alpha-amino dicarboxylic a clds and the assignment of characteristic

frequencies to the ·NH/ groups and the -coo· groupo involved ia

the work of Edsall ( 1938) on the Raman spectra of the amino acids

and related compounds in aqueous solution. As a result of these

spectroscopic studies, it may be accepted that alpha- amino

dicarboxylic acids in the solid state, or at their isoelcctric points in

aqueous sol ution exist almoat exclusively as the dipolar ions. As a

consequence of this dipola1· ion structure, many amino acids pos~ess

a characteristic absorption frequency at about 6. 3 microns which is 35

related to the -coo· g roup, as well ao a relatively weak absorption at about 4. 7 m icrons, which may be attributed to N.H frc<1uencies in the -NH3+ group (Koegel, Greenstein, Winity, Birnbaum and M cCallum, 1955).

In aspartic acid, the electronegative groups act upon tile N- H

s tretching vibrations of the ·NH + group with the 1·eaulting shift in 3 its absorption to longer wavelengtha a o they approach the alpha-amino

group. Hence for aspartic acid, this vibration absorbs a t 4. 85 and

5. 25 microns. As the number of methylene grOllpS between the

alpha~amino group and the elect1·onegative group increases the degr ee

of intera ction and magnitude of the wavel ength shift decreases. As a

consequence, glutamic acid has no band at 4. 7 m icrons for the N~H

s tl·etching- frequ-e-ncy;- AD the functional g-roups in a. homologous

series of amino acids approach each other spatially, oome type of

interaction occurs, r esulting in a progressively increasing

perturbation of the N·H deformation motion.

Aspartic acid has a sharp band a t 5. 9 m icrons which is

p1·obably rela ted to the vibrational frequencies of an unionized

carboxyl group. The dicar boxylic a cids may be expected to contain

not only ionized, but also an unionized carboxyl g roup. The l atter

absorb at 5. 76, 5. 80, 5. 92, 6. 00, and 6. 07 m icrons. Both 36

glutamic a nd aspartic a cids possess the 3. 3 micron band, indicating

an .. QH vibr a tion frequency.

The following assi gnments have been made by Koegel a nd his

workers in 1955:

TABLE I

Infrar ed Spectra Assignments for Glutamic and Aspartic Acid

Wavel ength (m icr ons) Assign ment

4. 85, 5. 25 N - H s t retching vibrations in - NH + 3 5. 76. 5. so. 5. 92 .. cooH 6. oo. 6. 07 5. 83. O. 03 (C 0 ) of -coo- ~5_. ~9~~~------r_e_la_·t_e_d_,t_o_._<.c__ ,N_. }_a_n_d__ ~( C___ O~ ) _f_r_e~q~· --- 6. 19, 0. 04 due to the antisymmetrical C 0 freq. o..f the c~rbox~lat Et_ion :J..:..2.0. o. 01 due to the sr!P-me~r ic ~ c 0 freq. 7. 14 due to the symmetrical COO stretching freq. 6. 36 due to the unsymmetrical COO stretching freq. . • -· . ~6.._:-~6~5------·---~N;...... ;;..~ · Xmmetric;~~rmation motion 6. 96 C- H bonding *8· 78 NH3 r ocking freq. *8. 85 ------~------~------" " " xl~0-. ~5-1------.....----~C~--N--s_t_r_e-tc_h_ i_n_g~fr_e_}l_U_~-n-c"""""~--...... ---- ..... x Work done by Tadastakeniahi (1960) on glutamic acid.

The absorbance obta ined in the IR spectra of aspartic a cid

closel y resembl es the work of Koegel in 1955. 37

T ABLE II

Absorbance Obtained in the Infra r ed Spectra of

Aspartic Acid

3. 3 5 microns shoul der 3. 43 II broad band, s t1·ong inte nsity 4. 85 II broad band, weak inte ns ity 5. 25 II broad ban d, wea k intensity 5. 93 II sharp band, s trong intensity 6. 06 II sharp band, medium intensity 6. 25 II broad band, medium intensity 6. 65 II sharp band, strong intensity 7. 03 " sharp band, s t rong inte nsity 7. 42 II sharp band, medium inte nsity 7. 57 II broad band, strong inte nsity 7. 0 1 II .. sharp\ ba nd, strong intens ity

L ikewise the absorbance of glutamic acid i s found to be the following.

TABLE III

Absorbance Obtaii1ed in the Infrared Spectra of

Glutam ic Acid

3. 32 m icrons .. s harp band, s trong inte ns ity 3. 70 II shoulder 6. 07 II s harp band, strong intensity 6. 30 II very weak band 6. 60 II s harp band, s trong inte ns ity 7 • 03 II sharp band, strong intensity 7. 42 II sharp band, medium inte nsity 7 • 57 II broad band, strong inte ns ity 8. 01 II sharp band, s trong intensity 38

The IR spe ctra of the [ Pt (HAsp) z] and [ Pd (HAsp) 2] chelates show some notable changes from the aspa rtic acid spech·a .

The N-H stretching frequencies do not appear at 4. 85 and 5. 25 microns and the N-H symmetrical deformation at 6. 65 microns and

the NH rocking frequencies at 8. 78 and 8. 85 microns, are for the 3 most part removed.

Simila1· discrepancies a re abo found when comparing the

spectra of the analogouo platinum and palladium chelates with that of

glutamic acid itself. Shifts are also found in the spectra of the

chelates at frequencies where absorption is due to the coo~ group

and possibly to the NH group. T hese changes a. t•e indicative of tho 3+ formation of the chelateo, since bonding of the metal ion with the

alpha -amino and neighbodng cartwxyla te grQ.Up of the _glutamic acid

would hinder any vibrational or rocking motion in these groups . CHAPTER V

SUMMARY

The glutamate and aspa1·tate chelates of palladium, platinum, and rhodium were synthesized by the metliods descdbed in tho previous sections. These involved refluxing approp1•iate s toichiometric amounto of K PdC1 , K PtC1 , and RhC1 · 4H 0 2 4 2 4 3 2 with the respective acids. A second method for p1•eparing bisaspartatopalladium (II), employing sodium aspartate and

K PdCJ. , was found. A oensitive pH adjustment was required 2 4 which was not necessary in the alternate method. 'l' he synthesis of the other chelates could not be accomplished using the sodium s alt of the a cids.

- The chelates were chara cterizecLhy correlating___ih~ theoretical and reported carbon and hydrogen el emental a na l ysis.

This also aided in determining the stereochemistry which had already been theoretically predicted fo1• the various chelates. It is suggested by the writer that the ligands behave as bidentates in the case of the te t racovalent species platinum and palladium, and tddenta te in the case of the hexacoordinating rhodium metal, although the latter is not conclusive. Hence the stereochemistry of the platinum and palladium chela tes is square planar while those of rhodium are octahedral. .All three metal s have two ligand molecules ..

40 associated with them, but further evidence is required in elucidating whether a monomer or a dimer is actually formed.

An increased stability of the aspartate chelatea compared to the glutamate chelatee was found. This is explained by the reduced inductive effect of the beta- carboxyl group in the longer carbon chain glutamic acid molecule. Being further removed from the donor groltps, its effect on the stability of the structure ie considerably decreased.

F inal characterization was effected by the use of infrared spectra. The bands due to the functional groups involved in chelation with the metal ions were shifted to a slightly different wavel ength, diminished in intensity, or disappea red almost entirely. BIBLIOGRAPHY

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* Ba s olo, F . and Pearaon, R. G. , Me chanism~ of Inorganic Reaction!_!, John Wiley and Sons, Inc., New York, i 958.

~Cartmell , E . and Fowlea, G. w. A. , ,Yalency and Mole cular Structu:t•es, 2nd Ed. , Butterworths , London, 1961.

Chaberek, S., Courtney, R. C. and Martell, A. E ., J . Am. Chem. Soc., 75, 2185 (1 953).

Chabcrek, S. and Martell, A. E ., J. Am. Chem. Soc., 74, 6021 (!952).

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Grai g, J . C. , --I)ur-jer, p-,, P ., Glazer, A. N. andJiorning ,_E~. ,_ J. Am. Chern. Soc., 83, 1871 (1961).

:kDay, Jr., M . c. and Sel bin, J., Th.::oretical Inorganic:_Chern!,_~ tiT, Reinhold Publishing Corporation, New York, 1962.

Diehl, H . , Chern. Revs. , 21, 90 ( 1937).

Dunn, T . M. , J. Chern. So.£:_ , 623 ( 1959).

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* Gilreath, E . S., Fundamenta!.£.2E.cepts of ~norg anic Chel'r!i.Pt.!..Y• McGraw-Hill, New York, 1958. 42

Grinberg, A. A. and Kate, N. N., ~est . Sektora P latiny i D~ Blagorod. Metal., Inst. Obshchei i Neorg. Khhn., Akad. Nauk. S. S. S. R., No. 29, 37-44 (1 955).

II Jorgensen, C . I<., Acta chem. acand. 1 O, 500 ( 1956).

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*Kirshner, S., Advances in the Chemie~1·y of the Coordination £ompounds, The Macmillan Co., New York, 1961.

~ewis , J. and Wilkins , R. G., Eds., M_odern Coordination Chemistry, Interscience Pub., Inc., New York, 1960.

Lumb, R. F . and Martell, A. E., l:_Phys. Chern., 57, 690 ( i 953).

!~!: M artell, A. E . a nd Calvin. M., Chemistry of t,he Metal Chel~t~ Compounds, P rentice- Hall, Inc., New Jersey, 1952.

!i!Nyberg, H. T ., Ccfola, M . and Sabine, D., Arch. Biochem. Bioenxs., 85, 82-8 (1 959).

Orgel, L. ~: ., J'. Chern. Phya. , 23, ( 1955) .

Owston, P . G., and Row, J . M., Acta crxot. Ca~,~ ~, 1~ 253 ( 1960).

P errin, D. D., J . Am. Chern. Soc., 3120 (1 958).

II Schaffer, C. E . and Jorgense n, C. K., J . lnorg. N';lclear Chern., 8, 143 (1 958).

Spacu, P . and Scherzer, 1., z. An01·g. Allaem. Chern., 319, 101 .. 6 (1 962).

Volshtein, L . M. and Anokhova, L . S., Zhur. Neorg. ~hill!•, 4, 1734-40 (1 959).

Volshtein, L . M . and Anoknova, L . S., Znur. ,Nec;>_:g. _Khim., 6, 300- 5 (1 961). 43

Volehte in, L . M. and Anokhova , L . S., Zhur . Neorg. Khi m .~ 325- 9 ( 1959).

Volshtein, L . M. and Vol dit1a, I. 0 ., Zhur . .~eo rs · K.~!~~ 2685- 8 (1962).

l it Refe r ences marke d with a s terisk were cons ulted directly. APPENDIX 4000 3000 2000 1500 CM-1 1000 900 800

7,-, .I 'J

1.0~----+-

') ....; 5 6 7 8 9 10 11 12 1 WAVELENGTH :lv\ICRONS)

~ Figure 7. Infrared Spectra of Aspart+ Acid U'\ l -r -

I

4000 3000 2000 1500 I CM-l 1000 900 800 t:;; I i I I I I I I I I 0.0 I j : I

l__ ' - ..:.---=-:...:. · - • r CO ~----~~ L: •- . 1' ::'~ '"T"'I -:..., v - - - i- 0 . ... , 0 0 • 7 ~1 1 · , · . =- · 1 3 .... - !::t~~ --;;-r=-- -=r:r_.__j__=rt-~..;.-rE*~_:__==E~c. =- ~~r! - ~ -2-=Jc=·--- -- I 4 5 6 7 8 9 10 11 12 1 VI AVELENGTH !MICRONS;

~

~ Figure 8 . Infrared Spectra of Glutamic Acid a- I 4000 3000 2000 1500 CM- 1 1000 900 800 ~ ,,,,,,,,,, 0.0 I I

r,...- \ -r·· -.. ~-'·t 7 ·--.---· , - 7 ~ -~ ·t ; ··t 1 -,... , ,...;..;-:~#11·--r·-,·-·+-··--'--· q ... ~ • lo . . I . . . ·r1 .· ·· . . . . I - . I . . ... I r:

I --'----~,...·r---~------~------.__. ___ . ....___ .. -.. .. __ • l- -- .. : .. :-: ~ :t .... - :: -.: ~- .. :.. -...... #- ... • ~

<:X:) t I 1 6 7 8 9 10 ll WAVELENGTH (tv\iCRONS)

~ Figure 9. Infrared S pectra of Bisaspartatoplatinum (II) -..1 ~- -~ I 4000 3000 2000 1500 CM-l 1000 900 800 I I l I l I I I l I I I " l t__t__[__j__Lj_l__Ll I 1 ! l I ! I I I I I ',

' - ~ ~ ~l .·:tiJiii!li T · ; 1 i1 : .litf~E.111!N r~!-4-!-W-i ~.. ,;.,~~ ~' i ,:_r ·~-- - ' +-;--;- . .,-- '-+++t ~ =-~ -..=.:- • ~ . r -- .10 ; ~ -~f-'''~++H' .,.....,.._._ 1' I- .. • i•• . I•i ' i : . • I •• - ·"t· ...... - -- -_-- .._ ...:-.t-+--*;- ___L_Ll_L_,_ •.....:_ -'f:P:tifF.,.. • • • tt· -~.--;~ ...... t -8"";. . . ___...... ,.._ -.~~-i~~--~~--~~~~~~~-+~~~~~--~-4~~~~~. ·r. - c=::.3Q.

~ _ --!-!-.;....t...... Lfln tIt' I ..•. -h --.... l ... .A . ' .. I 'r -: '" • ,, co.40 ·t-t++ !-..._ _.... -- ..... 50~-'"- r-1± -tf- --:{> -:t1-...... :r :'l. ..; f-H ...... ~ .60 --+-'----f'. !".. :::!. ~ .. .70-- ' ~'i i. .... 1,. ~~~~~~~~~+-~~~~~~~~~~~~~~~ - ~­ ,-o : t l I -- -, I' II! ! ' .,..---~' ------~ _!_1_!. I I' ' I J 1 I ~ ~ ffit- t.ort:n-rr --~..!". _...... ,_, -rf' I I Ill___,___ I I I " P-~1-~ - r-' ·j_ ·~_,;. ·-_;._;:,;; o::>1 1 ~ - ~!I i 1 11;- ~:-urrm~-:-~ TII:;:JJ: H '11 11 3 5 6 7 8 9 10 1 rl WAVELENGTH (MICRONS \

~ Figure 10. Infrared Spectra of Bisglutarnatoplatinurn (II) CXl r . , I • : 4()00 3000 2000 1500 CM-1 1000 900 800

~ .. 3 4 .J 6 7 8 9 10 11 12 I WAVELENGTH (JV,ICRONSJ

~ Figure 11. Infrared Spectra of Bisglu~ amatopalladium (II) -.D I I

- ~ r 4000 3000 2000 1500 CM-1 1000 900 800 L.,, I I I I I 1 L I f..' o.o ,j#l ' I I • ' f'i-,.

4' ' I J/1" , f r 1 ~ I f .-~ t ... riJ 11!1 15!.;A rh r- .10 .- w 4-l­ ·+-+-1- • c-;-· ..- "r .•--.---.- -·--t+ ·~1+:1=: ~ . 20 - H· ___._ -,.--, n11 ··;--r . _ -- . .i...l.-1-.'!:' ~~- _ . :.-=-~...... ++--"--,-~+--~ . ~ f-!- ;-r-.;,.. ·4~ ·:·..;:j:_ ~-J::~1:t-H-t+t--t4--H-: ~~ =--"'-----r- -·...... ~~ --·...- .- >-+ ......

~.30 1 :g~nE=t~E=E·s:a:a±uE·ts:E:t:Etji!:tl8J~j2:~--~:-~ · ~±- J.tt~t:··~ · ~ · · .. :¥, ·, ~ -~ ++ T·: ~ j , , : +++~ 0 4 -:-- : ~-:n- ... T:f.E i J 1 +~ ... -+-~ ... --~ -::.:.1 ~ ~= ~·~"*'"filib-:trp: t 01 , " • • • • • f] I : - : '~ 4 +-~ • ·;-;---;-~~ •-4.'-...-t-~• ~ ~~ +-:; 1 ~.40 . : : : ; ,:._ -+-i---rl--- ~~. -. _._:-:r,· +lit ~.50 ----~-~: ..!7 . ' ._i. + ~ -· ;--!-! -~:..t:t:E .60 ... - -1:$11= .70 ---. ~-· Et·±.. t .:;._:;--: . - -- - - _. l i: ffi-t-: 1 , j 1 1 i Ill~ i I • • < ~ . ' 1 r I\. I' ' • I I ,, 'I :~JTi · 1, ,·r ' I rr t t :· ' . ~ 0 1.0 I I ' +-t-t.;· t .. ~ • +·• - ...u-.t+::.t-r 00 t. 1 1 ' ! r: , , ~ 1 1 1 i ·· ' 1 1rn ,n , , T · T 1 • ., ,. ! 1 1 i • • • • 1 ; 1 3 4 5 6 7 8 9 10 11 12 1 WAVElENGTH (M!CRONS)

------~~---

(Jl Figure 1 2. Infrared Spe ctra of Bis aspf-- rtato palladium (II) from M e thod I 0 I

"" I 4000 3000 2000 1500 CM-1 1000 900 800 .L ~ l__l_ I I I I I I I I I I I I I I I I

t (j J 1 fi • 1 t iii .t • .i _Il l• i' , . I __I_· ·~ · .. ~:._l·.,.:.~ -r--l-t-+•t-· . - ___1_,__ . • I .._ 1- ...-!"t- ' . ~- t+ ~ ~-·· • ~ •.. •· • . '" ~ ... , ·----W_ _ ..;.~~- ~ I ~ -~ I --t- . ' --~-~--- ~-h-t. --· ~' : ~ • r.·, .~ · I -i- 9-i- f 1 j • t "- ...- •. ,..-r-::- ""'!"""f;-- ' j+~•t . ... ~

~t:~~~t+~~j:~~~4=~i:==~:t~:tt1:t!l:Ct1~t+4=tt4=~==tt~~jj~~~ r.+ ;...;- ~-~-t- I :-t~ . ~~====~~~~~~~~~~:-- : . . : 0 - ....,...t~.~-~ ,~ ' ' I ' .:.. -+ • ~ 4~ , ' - - ._ • t- ' • ' ~- ' ' . . ~ . ..~~t-!-+- - _l . '· ..__.;.,r--_._ . ' ,._ ---~- .. . ~ ~ ~- l'k: ,... -- . . . . --:-: ' !-+---~ -+-++-+-+- ._, f+~ ~ ~ -. ~ .. ~ ~ ... t . • -- ~ ;·· ..... ·.·~4- : ~·+-.;.t"~+;-:=--t-;.t'~-+-l--. + ... ~ ~- :t~-==~t=-~:t::.-:-:. ~ ~¥1~-:-~-: l ~-~- ·-~~ -~~~--: t t=-~1~ - , . . . . . : . ~ ~-- : , . . -....:.. ;:\.::.:;.;., .. ;.~- ~ :f:: :: r.,,. !.: _: · =~, ~ ,-t-!- -+ • -· -- -"-1::1;~_~. · . R ~- ~ • ._...... __ .. ~ -ft-71-..-~. ,.... --~...... ~:vt .;. ... ~-+- •· - ~ ~ , '" • • ,..,...... r--:-·_.__ _._ : ~.... _..._ ·lll · "--+·t-~-""P 'H1 ru- -~ :-N---'- -·----~...... ,..., -..-' 1. ,. W · h-1-' '~ .... : "~-...- ...-~ ... . ~-+ • ~-····c-i- , . · ,. ~ 7 ...... ~~ --• _.,_ -!""'-~ - ·' • • • · u 20 .. .L.l ~ -t . - -'-- - . . - .... ~ • ·1·--\11 . ,.... ~~ -.d~~ L-1*-"- ... ---!- -~' - ...... • .,...H-'-H-::gq: :·+t · "-·:-J:.I ·"-+-+ 4----· f+r'-~ ~. · ·· ~t"·: t;· ~~- ·t-+--'-1-'-tir. ·'-·.t;.. \f\1~+~ "r - U '~ '.· . ~ ~.. .._ ~c :·t:t r-1-! r-· r- ~~ t; ~ !.:r 1_ : _ ~ -· ~ :._- L::-- -,- -.; :-t··:;-~ -- ;-~· ·.=-..,. ~!- : .:. -: ..: ... · ~ - :- • tv;..J... f ~ .._: Z~ ·--+ q:: 1-F --.-- -~ - - , ' r · · ., .. 4 ~ 1' .. -~ .... ~- - ...... · -~ • .:.:;...::..:--~..: __:::, ~ ...... - - ::t~ ~ .... _... '!""' .. ~ f ..t~- ] ... ·:'!-~ .t •- ---r ~· ·~ --:---~!':": ~ - ~ - "" -- ... ,..t·•. . . co 30 .,... 4--+ .:;.. ~i::EE:~l:E~t.G :E ·-.:~~·f -.~.· r:.;:. ;:~ .=tSF.tr.£.::7.!:"'-:-!::.~.~:E-~, :L ~ · ±$. 4-r-!- • ~~l-+-~4 t~~r: f-_ ttt:~_ ;::_-- .. •-r: ~~~r_~ ~~ ;It.-£1...: =· :_t.:.::: :-_.r:-::: =~ :_:<::- ·-~ •• ·: _- ~: ... ~ · ~ t: · ~. ' -+-~ Tt: ~ . -tt' ~- ~ ~ - . .. +- ~ t . .+ ~- ~ifiil H" ~ ...... ~. •...... • ...... ~ • ~ ~- T t. ~ ...... ~ . t ~ ~ crJ0 40 . !--"-· :- 1-r!' --.-... t ~ \' t '-~~ .... llH-'t+ :-- -- .• ~---. ·- - ~ ...... ~ -· .•. t ~- -:· .• -~-

~ · m ~-- , .: - .tt:t::b:f .- ., ··:::..:. ~ =!. t:::: :-; '": :'!" :k ....;:::· -:-.;.: ~ ~ • .:;::: ~: ~!..:.:.: :-~ ; :..1 r T :.:: t :...;: :.-: ~- :· :: " 50 ' ...... : ' : -:::::: ::r- . ·~ t· tl't1:.._:;::r::t:+:-- ~ -+. ~ !'.: ---·r- .::...... : ,; ~ ... :. : :-r-:; -:::..;.t- ;.: :t:. ::1: ~ .:.! : ~:!.- • ~~ +-'- --;"t r • ·o ~ ' · · --:-,..... -- , ...._...... _-M-h - -. f--: ··_- .· ~ ~ -+--~-----~ r-:--c ·- •·- H . :.= -r---:= -- - -t--- - .... ~. ~- ~ '""';:....~ . r "·. --..~- · ·- - · 400 · · -- • -- .-:.:;: •..._.....:::: ...... _. 1 • ~ .60 T-•--+-- _,. ,,. ~.l. • ' .. - .::=: ..... • r __ :__ ·-- .:.:,.. - -·---. : · .... ·:= . - = = ., = =-- ::::.: --· - :r ?:t .:1 -· ;-;;; :: ";:-2:i:;:-:::- ~-; : t --:::: •. .. . .i_:;; .·:.;:.-_h· .-;:• 7 .70 ~ --+---. .. Blt::r.."·~. !-'"'~ .;.t:::t:~·.L·H Ji:: ·-=~ ...··• 'c..:.::t.... ·:. ·~"-' ,..·_i-O.::::-!~~.;:: . _-·~:-:-:+-t--=-·':"' ;t=:"'+-'t~·,.....;-=-=:t::::::::i:::::t .-r:-t: -- -::~-. ·-:-:!..~ t-.. · t'-;fi=~-... • t:: :- ~ . ~··· I I I I I ' l I I I I i . ; I ' I ' ~,j.. ! . ·~· ~ ·- I I ' I .• L I I I ' I I I •• I I I . I . ' j · 1 I . . '' .... :-- --- I I _1 I I - - . -- 1• 0 . ( .. ' . .!..:~~- -· I i '.I ---.-- ~-r-:...:.:..P.:~--:::..;:::j.:~~·- e·-~-- -: .. ..1·· -• . = 00LJJ::]·:• tli!i 'l :ll:j"Ji:it!!iio!':':> I .. ' l·~'ii I · ·i · 1: ! · I I .. ~1:: 1 : .! 3 4 5 6 7 8 9· 10 11 12 1 WAVELE~STH (MICRONS) ..

(Jt Figure 13. Infrared Spectra of Bisasp artatopalladium (II) from Method II .... 0

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/Dllt t 't \' 1D 3«;o. 30Zl .;(SO 3 :2/J, ~/0 Ol,::Zo c m - 1 c m - 1 F igure 15. Fig ure 14. 1 Ultraviolet Spectra of B isglutama topalladium (II) Ul traviolet Spec tra of B isaspartatopalladium (II)

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