Bose, K. S.

Dixit, N. S.

Patel, C. C.

English

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Indian Journal of ChemistryVol. 14A, July 1976, pp. 507-509Mode of Coordination of Isonitroso Group of4-][minopentane-2,3-dione-3-oxime in Cu(II) ComplexesN. S. DIXIT, K. S. BOSE & C. C. PATELDepartment of Inorganic & Physical Chemistry, Indian Institute of Science, Bangalore 560012Received 1 July 1975; accepted 1 December 1975ll- Isonitrosoacetylacetoneimine(4 - iminopentane - 2,3 - dione - 3 - oxime, HIAI) complexes ofcopper(II) of the types Cu(IAI)(IAI'), Cu(Me-IAI)(IAI') and Cu(Me-IAI)2' where IAl and IAI'represent: anions of N- and O-coordinated isonitrosoacetylacetoneimine respectively, have beenprepared and characterized. The complexes are monomeric, non-electrolytic and paramagnetic.Spectroscopic evidences suggest that the Iigands are coordinated through both nitrogen andoxygen of isonitroso groups in Cu(IAI)(IAI') and Cu(Me-IAI)(IAI'), and through nitrogen inCu(Me-IAI). giving a symmetric structure.ABLOV and Zubarev- have reported the jJrepa-ration of bis(isonitrosoacetylacetoneimino)-copper(II) and bis(N -methylisonitrosoace-tylacetoneimino)copper(II), but attempts to repeattheir methods did not succeed. Further, theseauthors did not consider the possibility of chelatelinkage isomerism in these complexes, the occurrenceof which has recently been shown+? in Ni(II) andPd(II) complexes of these ligands. Based on thestructures of dirnethylglyoxime complexes of Cu(II)7and Ni(II)8, Ablov and Zubarev have assigned sym-metric structures for the complexes with both theligands, coordinated through nitrogen of the isoni-troso group. In the present paper, we wish to reportour studies on Cu(II) complexes of isonitrosoacetyl-acetoneimine and its Nvmethyl derivative.Materials and MethodsIsonitrosoacetylacetone was prepared by themethod of Wolff et al.9• Copper acetate monohy-drate (Riedel, AR), methyl amine (Riedel, 33% aq.solution) and aq. ammonia (density 0·88 g/ml) wereused as such. Common solvents like methanol,chloroform (AR, BDH), etc., were used withoutfurther purification, while absolute alcohol and drybenzene were prepared by the standard procedures'".Molecular weights of the complexes in benzenewere determined cryoscopically. Conductivitymeasurements in acetone were carried out usingSiemen's conductivity bridge. The magnetic sus-ceptibilities of the complexes were determined byGouy technique, using Hg[Co(NCS)4] as a calibrant.Infrared and electronic spectra were recorded onCarl-Zeiss UR-lO and Unicam 700-A spectrophoto-meters respectively.Preparation of the complexes (i) Bis(isonitrosoacetyl-acetone imino)coj)per(II) [Cu(IAI)(IAI')J - Isonitro-soacetylacetone (2·2 g, ,....,0·0017 mole) dissolved inabsolute alcohol (10 ml) was added slowly toa solution of copper acetate monohydrate (1 g,,....,0·005 mole) and ammonia (3 ml, ,.....,28·0%) inabsolute alcohol. (80 ml). Red crystals of Cu(II)complex; were obtained when the solution was keptaside at room temperature for 4 hr. The crystalswere filtered, dried over cone. H2S04 and recrystal-lized from absolute alcohol as black needle shapedcrystals, yield 1·2 g (,.....,75%); [J-eff= 1·95 B.M.;m.p. 360°.(li) Bis(N - methylisonitrosoacetylacetoneimino) cop-per(Il) [Cu(iilie-IAI)2J - Methanol (20 ml) solutioncontaining isonitrosoacetylacetone (1·5 g, ,.....,0·011mole) and 33% aq. methyl amine (3 ml) was stir-red for 30 min. To this, copper acetate mono-hydrate (1 g, ,.....,0·005mole) in methanol (50 ml)was added slowly with constant stirring when abrown complex separated out immediately. It wasfiltered, dried over cone. H2S04 and recrystallizedfrom chloroform, yield 1·5 g (,.....,85%),[J-eff=1'93 B.M.m.p. 360°.Attempts to prepare similar complexes usinghigher alkyl amines by the above method gave blackoily material from which the desired complex couldnot be isolated.(iii) (N - Methylisonitrosoacetylacetoneimino)(isonitro-soacetylacetoneiminoi cnpper (II) [C u (211'e-I AI)(I A 1')J-Cu(IAI)(IAI') (0'317 g, 0·001 mole) andCu(lVIe-IAI)2 (0·345 g, 0·001 mole) were added todry benzene (25 ml) and the resulting suspensionstirred for 2 hr, when the solid complexes gotdissolved giving a dark red solution. It was keptovernight and red crystals of the complex were ob-tained when benzene was removed under reducedpressure. It was recrystallized twice from drybenzene at room temperature. The complex wasfound to be a single component, as indicated byTLC, yield 0'4g (,.....,60%);[J.eff=I·90; B.M.; m.p.172°.(iv) Amine-exchange reaction of Cu(I A 1)(1 AI')with methyl amine - Methyl amine (0·3 ml) wasadded to Cu(IAI)(IAI') (0·180 g) dissolved inchloroform-methanol (1 :1, 40 ml). It was kept for1 hr at room temperature. Brown solid complexwas obtained after partial removal of the solventsby passing dry air. The complex was filtered, driedover cone. H2S04 and recrystallized from chloroform.It was found to be identical with that obtained bythe direct method (ii), as indicated by their colour,507INDIAN J. CHEM., VOL. 14A, JULY 1976melting point, electronic and infrared spectra. Yield0·15 g ('""80%). -Results and DiscussionThe complexes are monomeric in benzene, non-electrolytic in acetone (AM~ 1 ohm I em- mole-')and paramagnetic ([J.eff 1·90-1·95 B.M.). Charac-terization data of the complexes are given in Table l.The molecular weight of Cu(Me-IAI)2 could not bedetermined because of its poor solubihty in benzene.The IR spectrum of Cu(IAI) (IAI') in mull showstwo NH frequencies at 3280 (m, b) and 3240 crrr'!(rn, sharp) and two C=O bands at 1680 (vs, b) and1650 em'? (m). The spectrum in chloroform exhibitsthese bands at 3350, 3292 and 1685, 1666 ern"! (sh)respectively. The occurrence of two NH and twoC=O bands suggests asymmetric mode of coordina-tion of the ligands to the metal, as in the case ofNi(IAI)(IAI') and Pd(IAI)(IAI').The close similarity of the IR spectra ofCu(MeIAI) (IAI') and Ni (Me-IAI) (IAT) is indicativeof structure (Ic) for the copper complex. The NHstretching frequency of Cu(Me-IAI)(IAI') in mulloccurs at 3270 cm " and that in chloroform at 3260cm-l. Two distinct C=O bands are observed at1680 (s}and 1668 cm! (s) in the mull spectrum anda broad band at 1689 em? in chloroform spectrum.The presence of two C=O bands in the mull spectrumsupports the asymmetric bonding in the Cu(II)complex. Out of the two C=O frequencies observedin these complexes, the higher frequency can beassigned to the O-coordinated and the lowerfrequency to the N -coordinated ligand. The occur-rence of C=O stretch at higher frequency in theO-coordinated ligand compared to Necoordinatedligand, may be attributed to the greater contributionof the resonance form II to the structure of theformer compared to the latter.In Ni(lA1)(1A1'), the two NH bands at 3229 (w,b)and 3365 ern"! (m, sharp) in the chloroform solutionspectrum have been assigned to the 0- and N-coor-o o-Il ICH3-C-C = N-O- +-----+ CH3-C = C-N = 0II IIIdinated isonitroso groups of the ligands respectively.In Cu(IA1)(IAI') and Cu(Me-IA1)(IA1') the NHfrequency of the O-coordinated ligand occurs at3292 and 3260 em? respectively. This may be dueto the weak hydrogen bonding between the oxygenof the projecting NO and the imine proton whichis in cis position. Possibly the larger ionic radiusof Cu(II) (0·72 A) compared to Ni(U) (0·68 A)causes weak hydrogen bonding. In agreement withthis, the observed bands are quite sharp in thechloroform solution spectrum.The strong band occurring around 1210 cm" inboth the copper complexes can be assigned to theOscoordinated NO frequency. Gurrien-! et al, haveassigned the band at a similar position to NO stretchin the metal complexes of l-nitroso- and 2-nitroso-'l-naphthcl where the ligands are shown to be coor-dinated through isonitroso oxygen.The structural identity of Cu(IA1) (lAI') andCu(Me-IAI)(IAI') is further supported by thesimilarity in their electronic spectra in chloroformmedium. The electronic bands in these complexesoccur around 41,300 (E = 24,000), 37,600 (sh) , 33,300 (sh) and 24,400 crrr" (E = 5970). However, pured-d bands could not be located, possibly due to theiroverlap by the charge transfer band at 24,400 crrr+.The complex Cu(Me-IAI)2 shows a single sharpC=O stretch at 1667 cm! in its mull spectrum andat 1676 em? in the chloroform solution spectrum,suggesting symmetric coordination of both theligand molecules. The position of the C=O bandcorresponds to the lower band observed in theCu(IAI)(IAI') and Cu(Me- 1AI)(IAI'). This suggeststhat both the ligands are coordinated through thenitrogen of the isonitroso group in Cu(Me-IA1)2'Such symmetrical structures have been assignedto analogous Pd(R-IAI)2 complexes, where R isnonbulky mono alkyl group", Recently, this typeof structure in one of the Pd(II) complexes, withR = C2Hs, has been confirmed by X-ray crystalstructure in our laboratory-''.The absence of O-coordinated NO stretchingfrequency around 1210 crrr? in Cu(Me-1A1)2 alsosuggests the different type of bonding of isonitrosogroup in this complex. The strong band around1150 cm-1 in Cu(Me-IAI)2 can be assigned to NOstretch of N-coordinated isonitroso group. Bandsat similar position have been assigned to the NOgroup in the Pd(II) complexes of isonitrosoethyl-methylketoimine and its alkyl derivatives wherethe ligands are coordinated through isonitrosonitrogen-". Further, this assignment compares wellwith a recent assignment of N-coordinated NO bandin the region 1130 crrr? of dimethylglyoximecomplexes of Pd(II) and Ni(U) for which normalTABLE 1 - CHARACTERIZATIONDATA OF THE COMPLEXESCalc. (%) Found (%)Metal C H N Metal C H N19'99 37'79 4·44 17·63 20·17 37·60 4-43 16·8818·37 41·67 5·24 16·20 18'47 41-40 5·20 16·2119·14 39·81 4·86 16·88 19·00 40·00 5·23 17-01ComplexCu (IAI) (IAl')Cu(Me-IAI)2Cu(Me-lAl) (lAl')508DIXIT et al.: ~-ISONITROSOACETYLACETONEIMINE COMPLEXES OF Cu(tI)coordinate analysis has been donew. However, itshould be noted that the NO frequency always occursas a coupled vibrations-". The electronic spec-trum of Cu(Me-IAI)2 exhibits bands at 39,700 (E =17,000) and 31,200 cm! (E = 8950). The simplicityof this spectrum as compared to that of the asymme-trically coordinated Cu(II) complexes also supportsthe symmetric structure of Cu(Me-IAI)2'One of the peculiarity of the present sys-tem is that Ni(IIJ forms complexes of the typeNi(R-IAI)(IAI') with monoalkyl or aryl substituentsbut does not form dialkylated or diarylated com-plexes of the type Ni(R-IAI)2' Pd(II), on the otherhand, forms complexes of the type Pd(R-IAI)2 withnonbulky alkyl groups and Pd(R-tAI)(IAI') withbulky alkyl or aryl substituents, Cu(II), however,forms both Cu(JvIe-IAI)(IAI') and Cu(Me-IAI)2 withmethyl substituent.References1. ABLOV,A. V. & ZUBAREV,V. N., Russ. J. inorg. Chem.,13 (1968), 1563.2. LACEY, M. J., MACDONALD, C. G., SHANNON,J. S. & COLLINS, P. J., Aust. J. Chem., 23 (1970),2279.3. BOSE, K. S., Ph.D. thesis, Indian Institute of Science,Bangaiore, 1970.4. IYENGAR, R. R., BOSE, K. S. & PATEL, C. C., Inorg.chim. Acta, 7 (1973), 3.5. IYENGAR, R. R., BOSE, K. S. & PATEL, C. C., J. inorg.nucl. Chem., (in press).6. BOSE, K. S., SHARMA, B. C. & PATEL, C. C., Inorg.Chem., 12 (1973), 120.7. FRASSON, E., BARD!, R. & BEZZI, S., Acta Crystallogr.,12 (1959), 201.8. GODYCKI, L. E. & RUNDLE, R. E., Acta Crystallogr., 6(1953), 487.9. WOLFF, L., BOCK, P., LORENTZ, G. & TARPPE, P.,Liebig's Ann., 325 (1902), 134.10. VOGEL, A. 1., Practical organic chemistry (Longmans,London), 1967.11. GURRIER, S. & SIVACAUSA,G., Inorg. chim. Acta, 5(1971), 650.12. DIXIT, N. S., MANOHAR,H. & PATEL, C. C. (to be pub-lished).13. SHARMA,B. C., BOSE, K. S. & PATEL, C. C., Indian J.Chem., 11 (1973), 1038.14. BIGOTTO, A., COSTA, G., GALASSO,V. & DE ATTI, G.,Spectrochim, Acta, 26A (1970), 1939.15. LACEY, M. J., MACDONALD,C. G. & SHANNON, J. S.,Aust. J. Chem., 26 (1973), 263.509

Mode of Coordination of Isonitroso Group of 4-Iminopentane-2,3-dione-3-oxime in Cu(II) Complexes

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Mode of Coordination of Isonitroso Group of 4-Iminopentane-2,3-dione-3-oxime in Cu(II) Complexes

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