Indian Journal of Chemistry Vol. 22A, June 1983, pp. 527-528 Bis- & Tris-chelates of Cobalt with Some Isonitrosoacetophenones C NATARAJAN*t & A NAZEER HUSSAIN Department of Inorganic Chemistry, Madurai Kamaraj'University, Madurai 625021 Received 27 August 1982; revised and accepted 3 January 1983 Cobalt complexes of the type, ML2 .nH 2 0[M =Co(II); L= anion of 4R-HINAP; HINAP = isonitrosoacetophenone; R= - H, - Me, -OMe, -CI, -Br and n=O, I], ML 2 .HL[M=Co(lI); HL=4- N0 2 HINAP] and ML,[M =Co(IIJ) and HL =4-MeHINAP] have been prepared and characterized. The IR data suggest N - and 0- bondings of the oximino group in one and the same molecule of the complex, the exception being 4-N02 substituted complex where bonding occurs through isonitroso nitrogen only. Substitution in the phenyl ring of the complexes produces shifts in V(C=0) which are related to the Hammett's substituent parameters. The magnetic moments observed for the cobalt(1I) complexes, except that of 4- N02 substituted complex, indicate distorted octahedral geometry. The PMR spectra of cobalt(III) chelates with 4-MeHINAP and 4- OMeHINAP suggest a cis octahedral structure for these complexes. The ambidentate behaviour of isonitrosornono- ketonea':" has generated considerable interest in the study of their metal chelates. In the metal chelates of these ligands, both N - and 0- bondings of the oximino group in one and the same molecule of the complex have been established using IR data. In the presence of isonitroso compounds, in slightly alkaline medium cobalt(II) readily undergoes oxidation by atmospheric oxygen 3 ,4. However no systematic approach has been made to establish the bonding and stereochemistry of bis- and tris-chelates of cobalt. We report herein a new set of cobalt(II) chelates of para-substituted isonitrosoacetophenones (HINAP) and few tris- chelates of cobalt(III). Coblat(II) acetate tetrahydrate used was of AR grade. The ligands and their sodium salts were prepared according to the reported procedures. Preparation of chelates: General method Cobalt(II) complexes were prepared by adding an aqueous solution of the sodium salt of the respective ligand (2 mmol) with stirring to an aqueous solution of the metal salt (1 mmol). The precipitated orange- yellow complexes were suction filtered, washed freely with water and dried over anhydrous calcium chloride. Yields were quantitative. The orange-yellow cobalt(III) complex of 4- MeHINAP was prepared by adding a neutralized [Present address: Extension Centre, Madurai Kamaraj University, St. John's College Campus, Palayamkottai 627002. ethanolic solution of the ligand (2 or 3 mmol) with stirring to an aqueous solution of metal(II) acetate (I mmol). The precipitated complex was filtered, washed liberally with water, little ethanol (96%) and finally recrystallized from ethanol; yield - 80%. The complex Co(4-0MeINAPh was prepared as reported in the literature". The water content of the complexes was determined from mass loss on heating these between 100 and 120°C.The room temperature magnetic moments were determined employing a Gouy balance with Hg[Co(CNS}4] as calibrant. IR spectra were recorded in KBr on a Perkin-Elmer 577 spectrophotometer, PMR spectra in CDCI 3 on a Perkin-Elmer R32 90 MHz spectrometer with TMS as the internal reference and electronic spectra in chloroform solution on a Perkin-Elmer 402 UV-VIS spectrophotometer. The analytical results are consistent with the assigned formulae (Table I). The complexes are non- electrolytes in DMF (10 -3 M solutions) and the molecular weight of parent complex Co(INAP)2 determined in benzene by cryoscopic method shows it to be monomeric. The ligand 4-N0 2 HINAP gives a highly paramagnetic (J1eff 5.4 B.M.) complex whose composition is compatible with 1:3 (metal-ligand) stoichiometry. The complex is insoluble in water and partially soluble in organic solvents. The IR spectra of the free ligands exhibit v(C=O) and v(NO) in the ranges 1642-1690and 922-1010 em -1 respectively. The latter corresponds to NO stretch Table I-Analytical and Magnetic Moment Data of the Complexes Complex Found (Calc.) (%) Ilcff (B.M.) M C H Co(INAP), 17.55 54.52 3.73 3.44 (16.59) (54.10) (3.41) Co(4-MeINAP),. H 2 O 15.66 53.98 4.112 3.28 (14.69) (53.87) (4.52) Co(4-0MeINAP)2· H 2 O 14.72 49.23 4.42 3.31 (13.60) (49.89) (4.19) Co(4-CIINAP),.H 2 O 13.61 43.87 2:25 3.37 (13.33) (43.46) (2.74) Co(4-BrINAP),.H 2 O 11.51 36.45 2.52 3.64 (11.10) (36.19) (2.28) Co(4-MeINAP), 11.02 59.98 4.02 dia (10.80) (59.45) (4.44) Co(4-N0 2 INAP), . 10.00 45.89 2.83 5.42 4-N0 2 HINAP (9.22) (45.08) (2.52) Metals were estimated as oxides 527