A NOVEL ONE-DIMENSIONAL NICKEL(II) ALTERNATING CHAIN FROM DISCRETE PYRAZOLATE-BASED DINUCLEAR COMPLEXES

Hexadentate dinucleating ligands that are based on a bridging pyrazola te bearing chelating side arms [3,5-(R2NCH2)(2)C3N2H2; R2N = Me2N(CH2) (3)NMe (HL1), Me2N(CH2)(2)NMe (HL2)] reacted with NiCl2 . 6H(2)O to yi eld complexes ClNi(mu-Cl)(mu-L-1)NiCl 1 ((Ni2LCl3)-Cl-1) and ClNi(mu-C l)(mu-L-2)NiCl 2 ((Ni2LCl3)-Cl-2), respectively. Depending on the side -arm chain length and the solvent used for crystallisation these compl exes either crystallised as dicrete bimetallic units (1) or were assem bled via di-mu-chloro linkages to form a tetranuclear compound (mu-Cl) -(mu-L-2)Ni(mu-Cl)(2)Ni(mu-Cl)(mu-L-2)NiCl] 2a ([(Ni2LCl3)-Cl-2](infin ity)) or a novel bridge-alternating one-dimensional chain [Ni(mu-Cl)(m u-L-1)Ni(mu-Cl)(2)](infinity) 2b ([(Ni2LCl3)-Cl-2](infinity)) in the s olid state. Variable-temperature magnetic susceptibility measurements revealed antiferromagnetic coupling within the basic mu-chloro-mu-pyra zolato bridged bimetallic framework in all cases and also suggested an tiferromagnetic superexchange propagated by the di-mu-chloro linkage i n 2b. The latter result is rationalised on the basis of the specific g eometric findings for this di-mu-chloro linkage, in particular the unu sually large Ni-Cl-Ni angle [101.37(4)degrees].