COMPLEXES OF NIOBIUM AND TANTALUM WITH CHLORIDE, SULFIDE AND OXIDE LIGANDS - SYNTHESIS AND CRYSTAL-STRUCTURE OF THE TRACHLORO)BIS-(ETA(2)-DISULFIDO)(MU-OXO)(MU-ETA(2) ETA(2)-DISULFIDO)BISMETALLATES [CL-2(S-2)NB(MU-O)MU-S-2)NB(S-2CL-2(2-) AND [CL-2(S-2)TA(MU-O)(MU-S-2)TA(S-2)CL-2](2-) AS THEIR TETRAPHENYLPHOSPHONIUM SALTS/

The preparation and X-ray structure analysis of the compounds [PPh4](2 )[Cl-2(S-2)Ta(mu-O)(mu-S-2)Ta(S-2)Cl-2] (1) and [PPh4](2)- [Cl-2(S-2)N b(mu-O)(mu-S-2)Nb(S-2)Cl-2] (2) are described. The anion of 1 was obta ined by heating a solution of TaCl5 with Li2S and S-8 in acetonitrile, while the reaction of NbCl5 with Li2S2 in acetonitrile gave the anion ic complex of 2. The two salts are isostructural and crystallize in th e monoclinic space group P2(1)/n with Z = 4. 1: a = 12.4263(3), b = 21 .5920(4), c = 19.1118(2) Angstrom, beta = 95.0760(10)degrees, V = 5107 .75(11) Angstrom(3), and R = 0.0286 for 5719 unique reflections with I > 2 sigma(I). 2. a = 12.4366(3), b = 21.5875(5), c = 19.0997(4) Angstr om, beta = 95.1340(10)degrees, V = 5107.2(2) Angstrom(3), and R = 0.04 21 for 7400 unique reflections with I>2 sigma(I). The metal complexes are dinuclear with bridging oxide and disulfide ligands in addition to terminal disulfide and chloride ligands and contain seven coordinate metal centers with a metal-metal distance of 3.2450(3) (1) and 3.2483( 4) Angstrom (2). (C) 1998 Elsevier Science S.A. All rights reserved.