Indian Journal of ChemistryVol, 17A, June 1979, pp. 576-579

Synthesis & Structural Studies of Some Diamine Complexes ofCo(ll) & Ni(II) Aryl & Nitroaryl Carboxylates

R. C. AGGARWAL* & V. CHANDRA SEKHARDepartment of Chemistry, Banaras :Ptindu University, Varanasi 221005.

Received 3 October 1978; accepted 25 November 1978

Mixed ligand complexes of the type MX2L2 where M is Co(II) or Ni(II), X is benzoate (OBz),f -napbtboate (Ivnap), or 0-, m- or p-nitrobenzoate (NB) and L is hydrazine, ethylenediamine(en) or o-phenylenediamine (OPD) have been prepared and characterized. Molar conductancesof ethylenediamine and o-phenylenediamine complexes in DMSO show that they are non-ionic.Magnetic and electronic spectral studies show that all the complexes are spin-free and octa-hedral. The carboxylate ion has been found to act as unidentate ligand, hydrazine as bridg-ing and ethylenediamine and a-phenylenediamine as chelating bidentate Iigands on the basisof IR studies.

METAL carboxylates and their mixed ligandcomplexes have attracted a lot of attentiondue to different modes of coordination of

the carboxylate ion in these complexes. Carboxy-late ion (R-COO-) is known to act as' unidentate,chelating or bridging bident ate ligand1'2. Althougha number of mixed ligand complexes of metalaliphatic carboxylates l~ave been fairly ~ell charac-terized>", little attention has been paid to suchcomplexes of metal aryl carboxylates. Except forthe d·~termination of formation constants of themixed ligand complex of hydrazin e with nickelbenzoate", no work appears to have been done onthe title complexes. A synthetic and structuralinvestigation of the diamine complexes of Co(II)and Ni(II) aryl carboxylates and nitrobenzoateshas therefore been undertaken to study the modeof bonding of carboxylate ion in .these co~plexes.Such an investigation is also c .msidered of. ll1t~restbecause it is expected to throw ltght on the ligationalbehaviour of diamines as co-ligands to aryl carboxy-lates.

Materials and Methods1-Naphthoic acid used was a Koch-Light reagent

while the other acids used were Schuchardt (Germany)reagents. Metal chlorides and all other chemicalswere BDH reazents or chemicals of equivalent purityEthanol and cthylenediamine were made anhydrousbefore use.

Preparation and analysis of complexes - So~j,?-msalts of the acids were prepared by the additionof an aqueous solution of sodiuIIl: hydroxide to t~esolution of acid in ethanol/water In 1:1 molar ratio.Ni(II) and Co(II) carboxylates .were obt~ined bymixing saturated aqueous ~JlutIOn. of NI(II) andCo(II) chlorides and appropnate sod-urn carboxylatein about 1.:2 molar ratio.

Hydrazine and a-phenylenediamine complexes ofmetal benzoates and isomeric nitrobenzoates were'

576

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prepared by adding an ethanolic solution of diamineto an aqueous solution of metal carboxylate keepingthe metal to diamine ratio just. above 1 :2. Metall-naphthoate complexes were prepared by mixingand stirring the ethanolic solution of diamine anda suspension of metal l-naphthoate in ethanol.keeping the diamine to metal ratio just above 2:1.

Ethylendiamirie complexes were prepared bymixing and stirring the ethanolic solution/suspensionof metal carboxylates and ethanolic solution ofethylenediamine in 1:2 molar ratio. The resultingsoluble complexes were precipitated by the additionof ether. Co(II) complexes of ethylenediaminebeing susceptible to oxidation, these were preparedin nitrogen atmosphere. All the complexes werewashed successively with ethanol and ether anddried in vacuo over c inc. H2S04,

Nickel and cobalt cmtents in the complexes wereestimated gravimetrically as nickel dimethyl glyoxi-m at e and cobalt anthranilate' respectively afterdestroy: g the orga ic matter first with aq uaregiaand then with cone. H2S04, Hydrazine was esti-mated volumetrically with KI03 (ref. 7) and nitrogenmicroanalytically. The analytical data are givenin Table 1.

Magnetic moments were determined at roomtemperature by Faraday's method using Hg [Co(NCS)4J as the calibrant and diamagnetic correctionswere estimated following the procedure of Figgisand Lewis". Conductance measurements were madeon a WT'vV conductivity meter. Magnetic momentsvalues are included in Table 1.

Electronic spectra were recorded on a Cary 14spectrophotometer in nujol. The positions of bandmaxima with their assignments and various spectralparameters calculated by the method outlined byLever? are given in Table 2. IR spectra of thecomplexes were obtained in KBr and nuiol on aPerkin-Elmer spectrophotometer model 621. TheIR absorption bands of diagnostic value in eluci-

r .AGGARWAL & CHANDRA SE'KHAR: Co(II) & Ni(H) COMPLEXES OF CARBOXYLATES

TABLE 1 - ANALYTICAL,COLOURAND MAGNETICMOMENTOF COMPLEXES

Complexes=t Colour Found (Calc.) (%) [LetI Complexes*t Colour Found (Calc.) (%) [LetI(BM) -------- (BM)

CofNi N CofNi N

Ni(N2H,1.(OBz). Grey 15·9 15·2 3·11 Co(en)2(ONB). Yellow 11·4 16·2 4·94(16·1) (15,4) (11-5) (16,4)

Co(N.H.).(OBz)2 Pink 15·7 14·8 5·20 Ni(en)2(MNBl. Blue 11·2 16·4 3·12(16,1) (15'3)

3·2}(11·3) (16,45)

Ni(N.H.).(1-nap)2 Grey 12·7 12·3 Ni(en).(PNB) •. Yellow 11·4 16·3 4·98(12·6) (12-05) (11'5) (16,4)

Co(N.H.).(1-napl. Pink 12·6 12·2 5·01 Ni(en)2(PNB)2 Blue 11·2 16·2 3·10(12,7) (12'0) (11-5) (16,45)

Ni(N2H.)2(ONB)2 Grey 12·7 18·2 ~'24 Co(en)2(PNB). Yellow 11·3 16·6 4·95(12,9) (18'5) (11-5) (16,4)

Co(N2H.)2(ONBj. Pink 12·6 18·4 5·22 Ni(OPD).(OBz). Grey 11·5 10·6 3'21(12'9) (18'5) (11·35) (10,8)

Ni(N.H.).(MNB). Grey 13·1 18·1 3-08 Co(OPD).(OBz). Brown 11·2 10'5 5·01(12,9) (18'5) (11-4) (10·8)

Co(N.H.).(MNB). Pink 12·7 18·6 :·14 Ni(OPD:.(: -nap). Grey 9·3 9·0 3·24(12'9) (18'5) (9'5) (9'1 )

Ni(N.H.).(PNB). Green 12·8 18·3 3·18 Co(OPD)2(1-nap). Brown 9·2 9·5 4·90(12'9) (18'5) (9'5) (9·1)

Co(N2H.).(PNB). Pink 13·0 18·6 5·06 Ni(OPD).(ONB). Grey 9·4 13·9 3·16(12'9) (18'5) (9·7) (13-85)

Ni(en).(OBz). Blue 13·9 13·1 3·06 CO(OPD)2(ONB). Brown 9·8 14·0 5·11(13'9) (13·3) (9'7) (13·8)

Co(en).).(OBz). Yellow 14·2 13-0 5·04 Ni(OPD).(MNB)2 Grey 9·3 13·6 3·22(14·0) (13,3') (9,7) (13-85)

Ni(en).{1-nap). Blue 11·4 10·6 3·09 C0(OPDl.(MNB). Brown 9-4 13·5 4·94(11-3) (10'75) (97) (13-5)

Co(en).{1-nap)2 Yellow 11-1 10·5 4·92 Ni(OPD).(PNB). Grey 9·5 13·7 3·19(11·33) (10,7) (9·7) (13·85)

Ni(en).(ONB) Blue 11·2 16·3 3·07 Co(OPD).(PNB), Brown 9·8 13-6 4·98(11·5) (16-45) (9,7) (13·8)

·OBz = benzoate; I-nap = I-naphthoate : ONB = o-nitrobenzoate; MNB = m-nitr<.,benzoate; PNB = p-nitroben'zoate;en = ethylenediamine; OPD = o-phenylcnediamine.

t Satisfactory analyses for h ydrazine were obtained in the case of hydrazino complexes.

TABLE 2 - ELECTRONICSPECTRALDATA ANDVARIOUSLIGAND-FIELDPARAMETERS

Complex vi(cm-i) v2(cm-i) va(cm-i) Dq(cm-i) B'(cm-i) ~ ~O(%) L.F.S.E.kjfmole

Ni(N.H.)s(OBz). 10150 17760 28570 1015 838·5 0·79 20·6 141·8Ni(N2H.la(1-nap). 10050 17390 27030 t005 951'3 0·90 9·99 140·4NilN2H.)2(ONB)2 9760 17390 26670 976 887·2 0'84 15·99 139·3Ni(N.H.).(MNB). 9980 17620 27630 998 819'7 0·77 22·39 142·5Ni(N.H.).(PNB). 10050 17760 27860 1005 837·3 0·79 20·71 143·5Ni(en)2(OBz). 10990 18520 27470 1099 868·0 0'82 17·80 153·6Ni(en).(l-nap). 11110 18180 28170 1111 901·3 0·85 14·65 155·2Ni(en)2(ONB). 10680 17620 27020 1068 840·0 0'80 20·46 152·5Ni(en)2(MNB)2 10810 17790 26180 ' 1081 769'3 0'73 27'16 154'5Ni(en)2(PNB)2 10720 17580 26680 1072 806·7 0·76 23·61 153·1Ni(OPD)2(OBz)2 9950 16670 26670 995 899'3 0'85 14·84 139·0

- Ni(OPDl.(1-nap). 9660 16390 26320 966 915'3 0'87 13'32 138·0Ni(OPD)2(ONB)2 10420 17540 24390 1042 711·3 0·67 32·65 148'8Ni(OPD).(MNB)2 10310 17240 26180 t031 832·7 0·79 21·06 147·2Ni(OPD)2(PNB)2 10400 18050 26320 1040 878·0 0'83 16'86 148·5Co(N.H,)2(OBz). 9260 19740* 20750 1048 847·2 0'88 12'39 99·86Co(N.H.)2(1-nap). 9220 19560* 19050 1034 729'8 0·75 25·03 98·51Co(N.H.).(ONB)2 9524 16390 21050 947·8 765·2 0'79 20·84 90·31Co(N.H.).(MNB). 9615 17180 21510 1086 876·4 0·91 9·36 103·5Co(N.H.).(PNB). 90tO 16610 20580 1017 851'3 0'88 11·95 96'81Co(en).(OBz). 9524 20110* 21370 1059 965'8 0·90 10'50 100·9Co(en).(l-nap). 9440 20110* 21120 1066 852'5 0'88 11·84 101·6Co(en).(ONB). 9480 20160* 20410 1068 808'3 0'84 16·40 101·7Co(en).(MNB)g 9050 19410* 20490 1036 849·4 0·88 12·16 98·72Co(en).(PNB). 9300 19810* 20920 1051 855'5 0·89 11-53 100·1Co(OPDlz(OBz). 9300 17790 23260 849·0 876·6 0·91 9·35 80'89Co(OPDlz(1-nap). 9620 17240 22120 821·0 818·1 0'85 15·40 80'50Co(OPDlz(ONB). 9259 16950 20830 1046 851·9 0·88 11·91 99·94Co(OPD).(MNB). 9070 16340 20200 1016 814·5 0·84 15·77 96'81CO(OPD)2(PNB). 8970 17540 20410 1014 840·9 0·87 13·04 96·61

*Calculated values employing Lever's methode.

S77

INDtAN r. CHEM., VOL. 17A, JUNE 1919

dating the bonding sites and their assignments aregiven in Table 3.

Results and DiscussionThe analytical data indicate 1:2 :2 (metal-car-

boxylate-diaminc) stoichiometry for all the. co:n-plexes. While the hydrazinc and ethylenediaminecomplexes do not melt u.ntil 250°, o-phenylen~-diamirie complexes melt in the range .168-220.Complexes of ethylenediamine are soluble m .watyr, .but those of hydrazine and o-phenylenediamineare insoluble. 'While the hydrazine complexes areinsoluble in common organic solvents as well as incoordinating solvents, ethylenediamine an~ o-phen:y-lenediamine complexes are freely soluble in coordi-nating solvents such as DMF, l?MSO ,<l:nd THF.The non-melting nature and the insolubility of thehydrazine complexes suggest that they are poly-meric, The molar conductance values of ethy-lenediamine and o-phenylenediamine complexes inDMSO lying in the range 1·17-4·50 mhos em- mole!indicate the non-ionic nature-" of these complexes,The room temperature magnetic m~ments of allthe complexes are normal and occur m the ranges3·06-3·24 and 4·90-5·22 B. M, respectively forNi(II) and Co(II) complexes indicating t~le spi,n-freeoctahedral gcometryv- of the metal' IOns m allthe complexes. . .

Electronic spectra - The electromc, ,spect,ra ofNi(II) complexes give three d-d. transitions in theregions 9660-11110, 16390-1851.0. and 2439~-28570cm", assignable to the transitions 3T2g+- Ag(vI},

3TIg(F)+-3A2g(V2) and 3TIgW)+-3A2g(V3) respectively.The positions and the assignments of these b,andsindicate octahedral geometry for all the NI(II) ,complexes-v-P. The octahedral geometry of tho~ecomplexes is further supported by the v2!VI ratiolying in the rangel3 1·65-1·78,

The electronic spectra of Co (II) complexes generally yield three d-d transitions in the regions 8970-9615 and 19050-23260 crrr+ which can be assigned tothe transitions 4T2g (F) +-4TIg (F) (VI)'4TIg(P)+-4TIg(F)(V3) respectively, characteristic of octahedral stereo-chemistry of Co(II) corr:plcxesI2,14. ~nother d-dtransition of weak intensity expected m the elec-tronic spectra of octahedral Co(II) complexes dueto the transition 4A2g+-4TIg(F)(V2) has b~en obser~edin eight of our fifteen Co(II) complexes m the region16340-17790 crrr '. The V2!VI ratio lying in therange? 1·72-2·15 also supports the proposed octa-hedral geometry for Co(II) complex:es, Dq valuesfor the mixed ligand field of the l':JI(I,I) com~lexeslying in the range 966-1111 cm! indicate NIN402chromophore for these complexe~]5, The ~o ~aluesindicate 9·35-32'65% covalency m the metalligandbonds of the present complexes,

IR spectra - Out of sever~l absorption ban~sexhibited by the carboxylate ion, only asymmetncand symmetric COO stretching frequencies are con-sidered of diagnostic valuer. When carboxylateion behaves as a unidentate ligand, the asymmetncstretching frequency is expecte~ to un~ergo apositive shift and the symmetric stretclung fre-

+Detailed IR data for all the compounds are available withthe authors.

578

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-:;:.0 O~

R-C'OI HZ H2 r/C-R

-, N-N"'M/ ""M....-'/' I"'-N_W"';'Oj'H2 H2

. ,...-:0 0:--,.R-C/' "C-R

'0 0"'-!.I)/0

R-C/ ....0

H2 I H2,...--N<, /N <, '

R M R<,N/I <, w .H2 H2

O C_R0-::/

(II: )M=Co(ll) OR Ni(II)

R'= CzH4 OR C6

H4

R=C6H5 ' C10H7OR

o-,m-, P -N02C6H4

quency a negative shift as compared to similar b~ndsin the ionic carboxylate-:". A careful comparisonof the IR spectra of our complexes with those ofcorresponding free carboxylate ions in the COOstretching region shows a positive shift (4-26 em-I)in the asymmetric stretching frequency and anegative shift (4-25 cm-I) in th.e symmetric s.tret?h-ins frequency indicating the unidentat e coordinationot carboxylate ion in these coml?lexes, The ,asym-metric and symmetric stretching !reque~cIe~ ofthe N02 group in the complexes of isomeric nitro-benzoates remain practically unchanged as comparedto their positions in the corresponding free nitro-benzoate ions suggesting the non-involvement ofthe -N02group in coordination in these complex:es,

The vN-H and 3NH2 modes undergo a negativeshift of the order of 20-132 and 2-26 cm! respec-tively as compared to their positi,ons, in th~ s~lut~onor vapour phase spectra of the d~am~nes, !ndlcatm~involvement of nitrogen(s) of diamines m c,oordl-nation, A negative shift in the vC-N mode ,m ~hespectra of ethylenediamine and o-phenylenedlaml~ecomplexes and a positive shift in vN-N mod~ inhydrazine complexes further support the coordina-tion of diamines through nitrogen (s), The occur-rence of a sinzle vC-N band in the spectra of ethy-lenediamine ;nd o-phenylenediamine complexes inthe rezions 1042-1074 and 1220-1265 cm! respec-tively ~nd the appearance of the vN -N barid in ~hebridging region (965-982 em-I) in the hydrazmecomplexes indicate the involvement of both thenitros'ens of the diamines in coordinatiori'<P. New

I absorption bands appearing in the regions 326-390and 276-306 crrr ! in the IR spectra of the complexesmay be assigned tentatively to vM-N and vM-Omodes respectivelyv-v.

n ~#"'-<:a-~

...'.AGGARWAL & CHANDRA SEKHAR: Co(tI) & Ni(1t) C0)\1PLEXES OF CARBOXYLATES

The carboxylate ion appears to have no affecton the mode of bonding of diamines as co-ligandsbecause the mode of bonding of diamines in thepresently investigated mixed ligand complexes isthe same as in our previously reported mixed ligandcomplexes19,20 of cobalt (II) and nickel(II) pseudo-halides. On the basis of the general behaviourof the complexes and physicochemical studies dis-cussed above the following structures (I and II)are proposed for the complexes.

AcknowledgementThe authors thank Prof. O. P. Malhotra, Head

of the Chemistry Department, for providing researchfacilities and Shri V. N. Mulay and Shri R. C. P.Bipin for microanalysis and recording of electronicand 1R spectra.

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