Nitrosophenol complexes of transition metal salts Mamdouh S. Masoud*, Sawsan S. Haggag and Ahmed M. Ramadan Chemistry Department, Faculty of Science, Alexandria University, Alexandria, Egypt Seham A. Mahmoud Physics Department, Faculty of Science, Alexandria University, Alexandria, Egypt Summary Complexes derived from 4-substituted-2-nitrosophenols, 3-Me-2-nitrosophenol, nitrosophyrogallol, nitrososali- cylic acid and nitrosogallic acid with cobalt(II), nickel(II) and copper(II) have been prepared and characterized by elemental analysis, electronic and vibrational spectra, together with magnetic susceptibility measurements. The e.s.r. spectra of the copper(II) complexes were investi- gated, and detailed thermal properties of selected complexes are discussed. Introduction Attention in our laboratory has escalated regarding the potential of nitroso complexes (1±15) . Owing to the role played by these complexes in the body and in biological molecules (16) , their structure and stereochemistry is a matter of considerable interest. The aim of this article is to explore the scope of the chelating properties of eleven nitroso compounds with cobalt(II), nickel(II) and cop- per(II) chloride salts based on elemental analysis, elec- tronic and e.s.r. spectra and magnetic susceptibility measurements. More information was obtained on the structures by studying their i.r. spectral and thermal behaviour. Experimental Synthesis of the ligands The structural formulae of the ligands, prepared by direct nitrosation of the appropriate phenol according to a published method (17) , are given in Figure 1. Synthesis of the metal complexes Cobalt, nickel and copper complexes were prepared by adding the required weight of metal chloride to an ap- propriate weight of the ligand in aqueous EtOH [e.g. the Co±ANP complex was prepared by adding the metal salt, CoCl 3 á 6H 2 O (2.38 g, 0.01 mol) dissolved in H 2 O (50 cm 3 ) to a solution of the ligand, ANP, (4.53 g, 0.03 mol) dissolved in EtOH (50 cm 3 ) at the re¯ux temperature for 45 min]. Boiling under re¯ux was con- tinued for a further 10 min with occasional stirring. The resulting solid complexes were then removed by ®ltra- tion, washed several times with EtOH followed by Et 2 O and dried under vacuum over P 4 O 10 . All the complexes possess high melting points (>270 °C) and are deeply coloured. The metal content was determined by the usual complexometric titration procedure (18,19) . Ele- mental analyses were obtained from the Microanalytical laboratory, Chemistry Department, Faculty of Science, Cairo University, Egypt. Physical measurements I.r. spectra (4000±200 cm )1 ) were recorded as KBr discs on a Perkin Elmer 1430 i.r. spectrophotometer. Nujol mull electronic absorption spectra were recorded over the 190±900 nm range according to the method de- scribed by Lee, Griswold and Kleinberg (20) . Molar magnetic susceptibilities, corrected for diamagnetism using Pascal's constants, were determined at room temperature (298 K) using Gouy's method. The e.s.r. spectra of the copper complexes (polycrystalline sam- ples) were measured at 298 K, and for some as frozen solutions at 77 K using a Varian (X-Band) spectro- meter. Diphenylpicrylhydrazyl (DPPH) was used as a reference to measure g 0 . Thermal studies The d.t.a. of the complexes were studied over the 300± 700 K range using a Heraeus d.t.a. 500 thermal ana- lyser. A sample (60 mg) was placed in a Pt crucible and N 2 (10 cm 3 min )1 ) was passed over it while heating at 15 °C min )1 . Results and discussion I.r. spectra The i.r. spectra of the nitroso compounds and their metal complexes exhibit multiple bands in the 3700± 2350 cm )1 region indicating the presence of strong intra- or intermolecular hydrogen bonding (21) . The broad m(OH) band in the other complexes, with no water, is owing to internal hydrogen bonding (21) . The carbonyl absorption in these compounds is assigned to the ketoxime structure. The mCAH mode is obscured by the syn m(OH) of oximes (22) . The strong band in the 1640±1580 cm )1 region, assigned to mC@N is owing to 0340±4285 Ó 1998 Chapman & Hall Figure 1. Structural formulae of the ligands. Transition Met. Chem., 23, 343±347 (1998) Nitrosophenol transition metal complexes 343 * Author to whom all correspondence should be directed.