UNSYMMETRICALLY SUBSTITUTED PYRAZOLATES - NICKEL(II) COMPLEXES OF A NOVEL DINUCLEATING LIGAND PROVIDING BOTH N-RICH AND S-RICH COORDINATIONSPHERES

An unsymmetric pyrazolate ligand with different chelating side arms in the 3 and 5 positions of the heterocycle [(EtSCH2CH2)(2)NCH2]-5-[(Et2 NCH2CH2)(2)NCH2]C3N2H2 (HL1)) and its symmetrical analogue {3,5-[( EtS CH2CH2)(2)NCH2](2)C3N2H2(HL2)} have been prepared. Upon reaction with NiCl2 . 6H(2)O they afforded dinuclear complexes [(Ni2LCl3)-Cl-1] 2 an d [(Ni2LCl3)-Cl-2] 1 that contain both a bridging pyrazolate and a bri dging chlorine atom. While all nickel(Ir) ions within the N2S2 compart ments of the primary ligands are six-co-ordinate, one of the amino sid e arms of L-1 in the former complex is non-co-ordinating, leaving the respective nickel centre in a square-pyramidal environment. This dangl ing arm is co-ordinated to the metal ion upon treatment of 2 with NaBP h4 due to substitution of the terminal chlorine atom to form [(Ni2LCl2 )-Cl-1][BPh4] 3. All new complexes were characterised by means of X-ra y crystallography; 2 and 3 represent rare examples of dinuclear comple xes exhibiting various kinds of asymmetry. The electrochemical and mag netic properties of the complexes are reported.