SPECTROSCOPIC AND MAGNETIC-PROPERTIES OF 2 FERROMAGNETICALLY COUPLED NICKEL(II) DIMERS [(NI(TERPY)(NCX)2)2] (TERPY = 2,2'-6',2''-TERPYRIDINE, X = S OR SE) - CRYSTAL-STRUCTURE OF THE THIOCYANATE

Two new binuclear nickel(II) complexes [{Ni(terpy)(NCX)2}2] (X = S or Se) have been prepared from 2,2':6',2"-terpyridine (terpy) ligand. The crystal structure of [{Ni(terpy)(NCS)2}2] 1 was solved by direct methods and refined by least-squares analysis to a discrepancy factor of 0.050. The crystals are triclinic, space group P1BAR, with lattice constants a = 8.822(2), b = 9.569(1), c = 10.906(1) angstrom, and alpha = 74.35(1), beta = 85.19(2), gamma = 78.75(2)-degrees. The dimer, whose halves are related by a crystallographic inversion centre, consists of two nickel atoms co-ordinated to two terpy ligands, two terminal NCS ligands and two end-to-end NCS bridging ligands. Each Ni(II) has a distorted-octahedral environment. The Ni...Ni distance is 5.633(3) angstrom and the bridging angles are 100.0(8) and 159(2)-degrees. The complex [{Ni(terpy)(NCSe)2}2] 2 was found to be isomorphous [a = 8.867(3), b = 9.592(4), c = 11.047(3) angstrom, alpha = 73.64(3), beta = 83.44(3) and gamma = 76.67(2)-degrees]. Magnetic susceptibility data, measured from 2 to 300 K, were fitted to the Ginsberg equation, giving the parameters J = +4.9 cm-1, D = -4.3 cm-1 and z'J' = +0.02 cm-1 (NCS) and J = +10.1 cm-1, D = -10.0 cm-1 and z'J' = +0.01 cm-1 (NCSe). The magnetic behaviour of these and related complexes is discussed and some magnetostructural trends are given.