Transition Met. Chem., 18, 107-109 (1993) 5-Aminopyrazole transition metal complexes 107 3,4-Dicyano-5-aminopyrazole complexes of anhydrous divalent transition metal chlorides and their triphenylphosphine derivatives Mohammed Shakir*, Saji P. Varkey and Devendra Kumar Division of Inorganic Chemistry, Department of Chemistry, Aligarh Muslim University, Aligarh-202 002, India Summary 3,4-Dicyano-5-aminopyrazole, H3,4(CN)z5NHzpz (L) reacts either with anhydrous MC12 or with [M(PPh3)aC12] to yield ML4C1 z complexes (M = Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd or Hg), whose monomeric and covalent natures have been confirmed by their solubility in most non-polar solvents and their low electrical conductivities. The bonding mode of substituted pyrazole is inferred from the position of the v(C=N) band in the i.r. spectra. The electronic spectra and the magnetic moments of these compounds were recorded. Introduction Recent interest in metal compounds containing coordinated heterocycles(1-3) has led researchers to synthesize a number of pyrazole and substituted pyrazole derivatives as poten- tial complexing agents. A variety of complexes of 2- monohaptopyrazoles Rpz (R = H, alkyl, aryl) (1) have been prepared by the interaction of metal salts with pyrazole (4). Coordination is believed to be through pyridyl nitrogen, i.e. N(2), of the pyrazole ring; this has been confirmed by X-ray crystallography (4). It has been reported that the number of pyrazole units coordinated to the metal is influenced by the nature of the counter ions, the nature of the metal ion and the pyrazole ring substituent (4). The complexes of 3,4-dimethyl pyrazole, H3,4-Me2Pz, and 3-methyl-5-aminopyrazole, R3Me5NHEPZ, with various trialkylboranes, have been reported (5) to bond through the pyrazole nitrogen N(2), except for 3-methyl-5-amino- pyrazole, Ph3Me5NH2pz, which is coordinated via the amino group. Recently we have described transition metal complexes of 4-cyano-5-aminopyrazole and 1,2-dihapto- 4-cyano-5-aminopyrazolide ion with various transition metal ions and their triphenylphosphine derivatives ~6-s). Herein we report the complexes of H3,4(CN)25NH2pz (2) with anhydrous divalent transition metal ions and their triphenylphosphine derivatives, in order to investigate the effect of the strong donor substituents on the possible coordination via pyridyl nitrogen N(2). CN CN H2N~CNs~ /,/3 H2N@ cN N--N N--N / R H (t) (2) (R =H,MejPh) Experimental The ligand 3,4-dicyano-5-aminopyrazole, H3,4(CN)2- 5NH2pz was prepared by the reported method (9). The purity of the ligand was checked by microanalysis, m.p. and * Author to whom all correspondence should be directed. i.r. spectral measurements. CrC12'H20, MnClz'4H20, FeC12' 6HeO, COC12"6H20, NiCl2" 6H2 O, CuC12 "2H2 O, ZnC12, CdC12 and HgC12 (BDH) were commercially pure samples. Metal salts were dehydrated with (Ac)20. The precursors, [M(PPh3)2] (M = Mn, Co, Ni, Cu, Zn, Cd or Hg) were prepared by the literature (~~ methods and identified on the basis of m.p., elemental analysis and i.r. spectral studies. All the solvents used were dried before use. Dichlorotetrakis( 3,4-dicyano-5-aminopyrazole ) metal(II) complexes [ML4CI2)[M = Cr(la), Mn(2a), Fe(3a), Co(4a), Ni(5a), Cu(6a), Zn(7a), Cd(8a), Hg(9a)) A solution of the ligand, L (0.045 tool) in EtOH (40 cm 3) was slowly added to a suspension of the anhydrous metal salts (0.01 tool) in THF (50 cm 3) at room temperature. The reaction mixture was stirred for 3 h in a closed reaction vessel under a dry N e atmosphere; the resulting solids were isolated by filtration, washed several times with EtOH, and then with Et20 and dried in vacuo. Dichlorotetrakis( 3,4-dic yano-5-aminop yrazole ) metal( I I ) complexes [ML4CI2][M = Mn(2a'), Co(4a'), Ni(5a'), Cu(6a'), Zn(7a'), Cd(8a'), Hg(9a') ] The precursor, [M(PPh3)2C12] (M = Mn, Co, Ni, Cu, Zn, Cd, Hg) (0.01 mol) dissolved in THF (75 cm 3) reacted with the ligand (L) solution (0.05 mol) in EtOH (50 cm 3) in a closed reaction vessel under a dry N 2 atmosphere at room temperature. The reaction mixture was constantly stirred for 1 h, and the resulting solid residue was washed several times with EtOH and dried in vacuo. The EtOH washings upon evaporation in vacuo left 2 mol equivalents of a colourless microcrystalline solid mass identified as PPh 3 on the basis of microanalysis, m.p. and i.r. spectral studies. Physical measurements Elemental analyses were performed in the Microanalytical Laboratory of CDRI, Lucknow, India. Metals and chlorides were determined volumetrically(14~and gravimetrically (1 s~, respectively. The i.r. spectra (4000-200 cm- 1) were recorded in KBr on a Perkin-Elmer-621 Spectrophotometer. Reflec- tance spectra of solid samples in MgO were recorded on a Zeiss VSU-2P spectrophotometer, and electronic spectra in CHC13 solutions were recorded on a Pye-Unicam-8800 spectrophotometer at room temperature. The electrical conductivities (10- 3 M solutions) in DMSO were measured using a Systronics type-302 conductivity bridge thermo- statted at 25 ~ C. Magnetic susceptibility measurements were carried out using a Faraday balance at 25 ~ C. Molecular weights of ML4C12 were determined with camphor as the solvent by the Rast method (16). 0340-4285 9 1993 Chapman & Hall