Indian Journal of ChemistryVol. 18A, September 1979, pp. 242-246

Metal Complexes of Copper(II), Nickel(II) & Cobalt(II) withLigands Derived from the Reactions of Diamines with

3-Hydroxyimino bu tane- 2 -~neH. C. RAI, J. CHAKRABARTI & B. SAHOO*

Department of Chemistry, Indian Institute of Technology, Kharagpur 721302

Received 10 January 1979; revised 13 March 1979; accepted 2 April 1979

4,7-Diaza-2,9-dihydroxyimino-3, 8-dimethyldeca-3, 7-diene, 4,8-diaza-2,10-dihydroxyimino-3,9-dimethylundeca-3,8-diene and bis (3-hydroxyimino-2-butylidine)-o-phenylenediamine when react with metal acetates yield inner complexsalts of the type, ML[M = Co(II), Ni(II) or Cu(II)l. The preparation of the complexes has been achieved by isolatingthe ligand first and then complexing the metal ion or by adopting an in situ method involving the metal ion catalysedtemplate syntheses of the ligand and simultaneous isolation of the complexes. Besides the inner complex salts,a series of nickel(II) complexes of the type, Ni(H2L)X2(X = Cl", Br-, 1- or NO;;> have been synthesised where theorganic ligands coordinate with the metal ion in their uncharged states. These complexes have been obtained bytreating ethanolic solution of the ligands with ethanolic solutions of nickel(II) salts in the molar ratio 1 : 1. A seriesof binuclear copper(II) complexes of the type, CuLCuX2 (X=CI- or Br) have been obtained as coloured crystallineproducts by treating an ethanolic solution of the corresponding copper(II) iuner complex salts, CuL, with ethanolicsolution of the respective copper(II) salts in equimolar quantities. Vibrational spectra of the Iigands and metalcomplexes suggest that in the iuner complex salts, the oxime ligand acts as an endo quadridentate ligand through itsN-atoms and in the complexes of the type, M(HzL)X2 with the uncharged ligand, the metal ions are coordinated ina similar way and a hydrogen bonded cyclic ring structure is formed. Electronic spectra and magnetic properties of thecomplexes have been studied.

METAL complexes with hydroxyimines (oximes)as ligands have been widely studied". The signi-ficant outcome of research in this field provides

substantial evidence that the oxime complexes possessthe ability to form organometallic derivatives and bindreversibly molecular oxygen to the metal centre>".A more recent investigation demonstrates that theycan act as complexing ligands for other metallicelements. The oximes are unique in their abilityto form encapsulation compounds+" many of whichpossess unusual properties. Sahoo and coworkersw="observed that dimethylglyoxime and acetylacetone-dioxime act as tetra-functional ligands and diacetyl-azinedioxime as a hexadentate ligand. The bis-complexes such as M(dmg)2and M (aado), and M,(daado); simulate as exo-bidentate and exo-quadri-dentate ligands respectively leading to the formationof binuclear, trinuclear and tetranuclear metal clus-ters. Inspite of highly stimulating works in this field,such investigations have been confined only to a fewoxime's which are, to some extent, structurally similarto glyoximes, This situation has prompted us tocarry out researches using oximes with differentstructural characteristics, such as imine oximes of thetype (I) obtained by the condensation of ethylene-diamine, propylenediami.ie and o-phenylenediaminewith 3-hydroxyiminobutane-2-one. These promis-ing ligands first act as endo-quadridentate Iigands.The metal complexes isolated this way, may furtheract as exo-bidentate ligands to yield metal clusters.

Earlier works on.the former two ligands are rather

242

,I

C.H) CH), /c- C

" ~ HrN N_O/.R\....N N-O

~ II 'H/c-c,

H)C I CH)

R ~ - (CH212-'-(C H2l)-, - 0- C&H4-

scarce and only one type of mononuclear nickel(II)complexes having the stoichiometry, NiLHX isknown, though cobalt (II) complexes having similarstoichiometry as well as inner complex salts areknown14'15.

Bis (3 - hydroxyimino - 2 - butylidene)-m-phenylenediamine and bis(3-hydroxyimino-2-butylidine)-p-phenylenediamine have been recently synthesised inthis laboratory. These two ligands form binuclearand tetranuclear complexes with a variety of metalions and the results will be communicated later.

Materials and MethodsEthylenediamine, propylenediamine and o-pheny-

lenediamine were of BDH quality. All other chemi-cals were of reagent grade. Nilz.6HzO was preparedby the metathetical reaction of alcoholic solutionof Ni(N03)z. 6HzO and sodium iodide and filteringoff the precipitated sodium nitrate.

The ligand 4, 7-diaza-2,9-dihydroxyimino-3,8-dimethyldeca-3,7-diene was prepared by the literature

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rRAI et al. : IMINE OXIME COMPLEXES OF Cu(lI), Ni (II) & Co (II)

method=s m.p. 240-42° (lit. m. p. 242°). It analysedsatisfactorily for C1oH18NP2' 4, 8-Diaza-2, 10- dihy-droxyimino- 3, 9- dimethylundeca- 3,8-diene wasalso prepared as per literature procedure'v-; m. p.166-68° (lit. m.p. 66°) 'Cn H2o N4 O2, Bis(3-hy-droxyimino -2- butylidene)-o- phenylenediamine wasprepared similarly; m.p. 178-80° (lit. m. p. 180-82°),C14 HIS N4 O2,

Preparation and isolation of complexes - Uniforgnprocedure has been adopted to -synthesise the comp-lexes of the type, ML [M = Co (II), Ni (II) and Cu(II)]. The method of preparation of one suchcomplex is given below.

(4, 7-Diaza-2, 9-dihydroxyiminato-3, 8-dimethyl-deca-3,7-diene)copper (II) - The ligand (2.26 g,0.01 mol) was dissolved in a minimum amount ofabsolute ethyl alcohol by warming. To the ligandsolution, an alcoholic or aqueous solution of cupricacetate monohydrate (2.0 g, 0.01 mol) was added.A green crystalline compound was formed in a fewminutes and its quantity- increased on standing. Itwas filtered, washed with small quantities of ethylalcohol and finally washed with ether and analysedafter drying. In the preparation of other complexessolid compounds were not always formed immedia-tely, but appeared on standing for some time.

Preparation of complexes of the type, Cu(L)-CuX2 (X=CI-, Br: or NO:;) - The following generalprocedure was adopted for the preparation of allthese complexes.

Dichloro[(4,7 -diaza- ·2,9-dihydroxyiminato - 3,8-dimethyldeca-3,7 - diene)copper (II)]copper (II) [Cu(L')- CuCI2] - (4,7- Diaza-2, 9-dihydroxyiminato-3,9-dimethyl deca-3,7-diene)copper (II) (1.44 g, 0.005mol) was dissolved in ethanol and to it an ethanolicsolution of cupric chloride dihydrate (0.85 g, 0.005mol) was added with constant stirring. A greencrystalline solid was obtained which was filtered,washed with small quantities of ethanol followed byether and dried in vacuo.

Preparation of complexes of the type, Ni (H2L)X2(X=CI-,Br-,l- or NO:;) - The corresponding metalsalt solution (0.01 mol) in absolute ethyl alcohol wasmixed with a warm ale. solution of the appropriateligand (0.01 mol) and the mixture vigorously shaken.The colour of the solution immediately changed tored or dark brown. The solution on being allowedto stand for a few minutes gave red or dark browncrystals which were filtered, washed with ethanol andfinally washed with solvent ether and dried in vacuo.

Results and DiscussionThe analytical data, colour and magnetic moment

data of the compounds obtained are listed in Table l.The complexes Ni(H2L)X2 which are obtained in

dry alcoholic medium are unstable in aqueous solu-tion and in mild basic solutions such as in the presenceof Na2C03 or sodium acetate they transform intothe inner complex species. The complexes of thetype, Ni(H2L)X2 are paramagnetic and octahedralin sharp contrast to inner complex salts which arediamagnetic and square planar. Repeated attemptsto prepare macrocyclic complexes with boric esters,however failed.

I

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It is significant to note that the inner complex salts'ofCu (II) have been found to further act as exo-biden-tate chelating agents to give binuclear clusters of thetype, CuLCuX2 and a series of such complexes havebeen isolated.

Infrared spectraj of the complexes of the type, ML[M = Cu (II), Ni (II), Co (II)], Ni(H2L)2X2 and-CuLCuX2 have been recorded in the region 4000-400.The spectra. of 3-hydroxyiminobutane-2 one and bis(3-hydroxyimino-2-butylidene) - 0 - phenylenediaminehave been recored which serve as useful guides forband assignments. The spectra of 4, 7 - diaza- 2,9-dihydroxyimino-3, 8-dimethyl deca-3,7-diene and 4,8-diaza-2, 1O-dihydroxyimino-3,9- dimethylundeca - 3,8-diene could not be obtained since they decomposedon exposure to atomosphere due to absorption ofmoisture. Although the IR spectra of all the complexesare quite complex, structurally important vibrationalbands such as v(O-H), N-OH scissoring. v(c.· N) andv(N-O) are quite discernible and provide unequivocalevidence concerning the nature of bonding of theligands to the metal ions.

The complexes of the type, Ni (H2L)X2 show astrong and broad band centred~3380. The bandcan be assigned to vO-H of the N-OH group involvedin hydrogen bonding, most probably intramolecularin nature and suggests that the ligand occurs in itsneutral form. Intramolecular hydrogen bonding inoxime complexes where the protons of .the N-OHgroups have not been ionised or partially ionisedsuch as Ni (Hdmg), and related complexes are nowwell established-t-" and have been observed in thesame region.

The IR spectrum of 3-hydroxyinino-butane-2-oneshows a group of two bands located respectively at3410 and 3350 which are fairly broad and strongimplying hydrogen bonded structure involving theN-OH group. In the present series of complexes, theabove assignment gains further support from the factthat in the inner complex salts of the type, ML, andbinuclear copper (Il) complexes of the type, CuLCuX2,these bands fully disappear and the ligands occur asbinegative charged ions. ,

The spectra of the ligand bis(3-hydroxyimino-2-butylidenej-o-phenylenediamine and the complexesof the type, Ni (H2L)X2 show an absorption band ofmedium intensity ~ 1680while a common aspect, of allthe spectra of other types of complexes, i. e. ML andCuLCuX2 is the disappearance of this band fromthis position. This characteristic behaviour leadsus to believe that this band arises due to N-OH defor-mation vibrations. Earlier studies on acetylace-tonedioximato ,- and diacetylazinedioximato metalchelates1D-13containing the ligands in the neutral formshow the N-OH deformation vibration ~ 1700. Thisband disappears from the spectra ofthe inner complexsalts.

The spectra of the ligand as well as of the metalcomplexes in the frequency region 1650-900 are mostvaluable for the elucidation of structure and bonding.In the spectra of all the metal complexes of theligands, 4,7- diaza-2,9- dihydroxyirnino-3,8- dimethyl

t IR Vmax in ern">

243

INDIAN J. CHEM., VOL. 18A, SEPTEMBER 1979

TABLE 1- ANALYrICAL DATA AND MAONETIC Mo~mNT DATA OF THE CoMPLEXES

[The compounds were analysed by standard procedures-s. Magnetic susceptibility was measured by a Gouy Balanceusing HgCo(CNS), as calibrant]

81 ComplexNo.

12

Cu (L')Cu (U)

Colour

GreenYello-wishgreendo

Red

doReddish-brownredDarkbrown

doGreenGreyishgreenGreen

YellowishgreenBrownishgreenGreen

dododo

RedBrownDarkbrownOrangeredRedDarkbrownDarkredYellowishgreenReddishbrownDark red

do, Dark

brown

Metal (%) N (%) Oxime (%) Halogen co l1eff

22.6521.62

Found Calc. Found Calc. Found Calc. Found Calc.

18.7220.24

20.1217.31

21.2219.4217.23

29.5024.35

26.2228.45

24.52

25.7627.3422.3124.5216.9813.7211.20

14.86

16.4513.02

11.20

14.52

14.91

12.5210.4113.12

22.0921.U6

18.9320.77

19.7817.75

20.8219.8417.80

30.0924.85

26.7429.13

24.24

25.9727.0222.7224.2916.5013.2010.93

14.35

15.8812.79

10.67

13.89

14.54

11.9110.0412.85

20.1318.92

17.0019.40

19.0017.23

20.1519.2216.72

13.6211.20

17.5812.60

10.93

13 .4112.309.82

16.5215.4512.8210.56

21.10

15.6212.46

10.00

20.12

13.91

11.0010.0018.52

L' '4,7-diaza-2,9-dihydroxyimino-3,8-dimethyldeca-3,7-dieneU 4,8-diaza-2,1 0-dihydroxyimino-3,9-dimethylundeca-3,8-dieneV' Bis (3-hydroxyimino-2-butylidene)-o-phenylenediamine

19.4718.58

16.6919.81

18.8816.93

19.8018.8716.92

13.2710.96

17.6812.84

10.69

17.1811.9110.0216.0615.7412.5910.43

20.55

15.1512.21

10.18

19.87

13.87

11.379.58

18.40

23.78

22.4520.41

23.8222.8120.51

18.1214.2311.94

15.62

17.3214.10

11.45

15.24

15.92

12.8610.9813.86

23.34

22.2419.95

23.3322.2319.94

18.5614.8512.29

16.14

17.8514.38

11.99

15.62

16.39

13.4011.2914.45

17.1230.82

15.92

30.00

15.5228.00

19.6035.2745.10

18.9535.25

44.71

17.85

33.1542.21

1.731.83

1.82Diamag-

neticdodo

1.931.962.10

16.83 1.7031.31 1.60

1.9016.29 1.80

30.54 1.90

1.7515.11 1.8528.63 1.80

1.7519.96 2.903.97 2.85

46.95 2.80

2.90

19.21 2.8234.87 3.00

45.81 2.95

2.90

17.59 2.85

32.47 2.8043.12 2.95

3.00

34

56

789

1011

1213

14

15161718192021

22

2324

25

26

27

282930

Cu (L")Ni (V)

Ni (U)Ni (L")

Co (L')Co (U)Co (V")

Cu (L') CuCI.Cu (V) CuBr.

Cu (L') Cu (NOJ.Cu (U) CuCI.

Cu (L") CuBr.

Cu (L") Cu (NO.).Cu (U') CuCI.Cu (L") con-,Cu (L") Cu (NO,).Ni (L' Ht) CI.Ni (V HI)Br.Ni (L' HI) Iz

Ni (L' lis) (NO,).

Ni (L' Hz)CI.Ni(U HI) Br:

Ni (U n,n,Ni (U HI) (NO.).

Ni (V' HI) CII

Nl (L" HI) Br.Ni (L" Hz)I.Ni (V"Hz) (NO.).

deca-3,7-diene, and 4,8-diaza-2,1O-dihydroxyimino-3,9-dimethyldeca-3,7-diene there appear two sharpbands of medium to strong intensity-c 1600 and 1500respectively. Considering their sharpness and intensity, they have been assigned to the vC zz: N. As struc-tures of the ligands would show, the ligands containtwo kinds of C :.:..:'N groups relating to azomethineand oxime groups. The location of these bands near1600 and 1500, clearly manifest that the vibrationalenergies of these groups are significantly differentfrom each other. Analyses of the available data onstructurally related molecules such as: H2dmg and lowschiff bases lead us to assign the high frequency andfrequency bands respectively to azomethine and oximeC :::'N groups. The vC ",-.'N due to C = N-OH group

244

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in H2 dmg appears at 1450 which shifts to a higherfrequency region in the trinuclear dimethylglyoxi-mato complexes and appears in the region 1590-1550 cm-1 giving further support to the above assign-ment.

The spectral features of the ligand, bis (3-hydroxyi-mino-2-butylidene)-o-phenylenediamine and its metalcomplexes in the region 1600-1450 are relativelymore complex. In the free ligand there are twobands near 1635 and 1460 respectively which aremost perturbed on complex formation C~v 30-40cm") and in a similar way, these bands are attributedto azomethine and oxime C = N group stretchingvibrations respectively. Besides these two bands,four additional bands have been observed which are

RAI et at. : IMINE OXIME COMPLEXES OF Cu (II), Ni (II) & Co (II)

characteristic of phenyl ring vibrations. The fourbands in the spectra of bis (3-hydroxyimino-2- buty-lidene)-o-phenylene diamine are located near 15801570, 1500 and 1440 respectively. The first andlast two bands are of medium intensity whereas thesecond band is very weak and appears in the formof a shoulder. These bands are much less affectedin ;the metal complexes.

In the series of metal complexes of the type, ML,the high frequency C ~. N band shifts to a 10YVtrfrequency region and the low frequency oximeC.,:,:.:' N band undergoes a blue shift. These changesappear to be caused by change in electronic environ-ment on account of co-ordination with the metalions. It is believed that the oxime ligands are bondedby donating their nonbonding electron pairs withthe simultaneous metal ligand electron interactions.

These spectral features lead us to conclude that theIigands and their inner complex salts of the type ML,have structures of the type (II). The shift in vC :..::'Nand existence of hydrogen bonded O-H groups asevidenced by the IR spectra of the nickel (II) com-plexes of the type, Ni(H2L)X2' clearly manifest ahydrogen bonded macrocyclic ring structure forthese metal complexes as shown in structure (III).

The band around 1370 which is present in thespectra of 3-hydroxyiminobutane-2-one and all themetal complexes are easily recognisable as due toeH3 deformation vibration.

The medium intensity:bands located at 1300-1200may be attributed to C-CR3 stretching or CH3 rockingmodes. Besides these bands, in the spectra of bis{3-hydroxyimino-2-butylidene) - 0 - phenylenediamineand its metal complexes, an additional band.at 1250 has been observed and assigned to C-H in-plane vibrations of the phenyl ring. Another band ofconsiderable intensity which appears in the spectraof bis(3-hydroxyimino-2-butylidene )o-phenylenedia-mine and its metal complexes located at 770 has been.assigned to C-H out-of-plane vibration.

As to the spectra of the complexes, the most interes-ting band is due to vN-O, as this band would be mostinformative on the structure of the complexes as wellas bonding between inner complexes of copper(II)with the copper (II) salts in their respective binucleardusters. In the spectra of the complexes as well as theligand, bis(3-hydroxyimino-2-butylidene)-o-pheny-lenediamine three distinct bands appear in the region1100-900, the strongest one being the middle one andmost susceptible to change on co-ordination. Thisband, in our opinion, arises due to vN-O. In theligand, bis(3-hydroxyimino-2-butylidene)-o-phen-ylenediamine, this band appears at 1010 and ininner complex salts of nickel(II) of the type,Ni(H2L)X2, this band moves to a higher frequencyregion appearing in the region 1120-1090. In 3-hydroxyiminobutane-2-one, this band appears at1020. In the complexes, Ni(L'H2) X2 and Ni(UH2)X2 this band appears in the region 1115-1095. Itis most striking to observe that in all the complexes ofthe type, CuLCuX2, there is a decrease in the absorp-tion frequency of this band and the band appearsin the region 1040-1000which undoubtedly occurs dueto the formation of new links between the copper(II)inner complexes and copper(II) salts. This criterion

(

when taken into account are reminiscent of the factthat the inner complex salts act as exobidentateligands giving rise to binuclear clusters which arepostulated to possess the structure of the type (IV).

The binuclear complexes of copper(II) havemagnetic moments in the region 1.7 to 1.9 B. M.per copper atom and the ground term is 2D. Theelectronic spectra of the complexes have been studiedin the ligand field region 10,000-25,000. In all casesthe spectra consist of two broad ligand field bands:the first in the region 12000-12700 and the second inthe region 17,000-17,800. These spectral featuresresemble those reported for the bi- and tri- nuclearschiff base metal clusters19,'2o and lead us to believethat the copper(II) ions are in similar ligand fieldenvironments respectively. Both these bands arise dueto d-d transitions differing in their energies due to diffe-rent ligand fields. It would be reasonable to say whilethe high frequency band arises for the chromophoreCuN4 in D4h symmetry, the low frequency band ori-ginates due to the chromophore, CU02X2 under alower symmetry such as C2•

A single broad band in the electronic spectra ofinner complex salts of copper (II), centred-. ...}4,000has been attributed to the ligand field band due tothe chromophore CuN4• The broad band whichshows considerable structure represents two or threesuperposed absorptions.. The band is comparableboth in position and width with the earlier reportedplanar copper(II) complexes and lead us to believethat all the inner complex salts of copper(II) areessentially planar.

The nickel(II) complexes of the type, Ni (H2L)X2with uncharged ligand show magnetic moments inthe range 2.7-3.1 B. M. at room temperature, sug-gesting octahedral arrangement of the ligand atomsaround the central nickel(II) ion. The electronicspectra consist of three bands, one in the region13,000-14,100, the next one in the vicinity of 20,000followed by a strong intense band near 24,000. Theband in the lower frequency region can be assignedto the transition 3A2g~3Blg whereas the higher

245

INDIAN J.CHEM., VOL. 18A, SEPTEMBER 1979.

quency band can be assigned to the transition3Eg +- 3B11J • 3A2!1 and 3Eg are the two splitcomponents of 3TlIJ state in octahedral field upontetragonal distortion and thus the appearance oftwo bands in the region 12,000-20,000 suggeetsthe central nickel (II) ion to be present in an octahed-ral field with certain amount of tetragonal distortion.The band at 24,000 can be assigned to the transition~Tlg (P) +- 3A2U which in some cases overlaps the.strong charge transfer bands. ,

The nickel (II) inner complexes are diamagneticand possess a singlet ground term IAIg• The elect-ronic spectra of these complexes have been measuredin the range 10,000-25,000. The spectra consistsof a broad band in the region 20,000-22,000 and canbe reasonably interpreted in the light of the develop-ment for planar nickel (II) complexes. The widthof the spectra manifests that the band represents agroup of two to three transitions assignable to thetransitions, IAlg -* lA2g, IAII! -* l:B21! and IAII! -*1 Egunder a square planar environment possessing thechromo ph ore, Ni N421'22.

The cobalt (II) inner complex salts are all of lowspin type possessing magnetic moments in the range1 .9 to 2. 1 B. M. The spectra show a broad band inthe region 20,000-22,000 with some amountof structure which manifests that the cobalt (II)ion is placed in a square planar ligand field. Thespectral data can be logically assigned to a numberof spin-allowed transitions from the ground state2A2• However the high intensity of these bands leadus to believe that one more charge transfer tran-sitions partly contribute to this part of the spectra.It is likely that these ligands possess low energy 7t*orbitals. The third ionisation potential energy ofcobalt/If) ion being low, the charge transfer bandmay be metal-s-ligand in nature.

246

I

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