A TRIS(THIOXANTHATE) OF NICKEL(II) AND ITS TRANSFORMATION TO A DINUCLEAR TRITHIOCARBONATE COMPLEX - SYNTHESIS AND STRUCTURE OF [ET4N]2[NI2(SET)2(CS3)2]

The tris(thioxanthate)nickel(II) salt [Et4N][Ni(txn)3] has been synthesized. The S6-coordinated bivalent metal center (2.97-mu(B)) is oxidizable, the E1/2 of the Ni(III)(txn)3-Ni(II)(txn)3- couple being 0.09 V vs SCE (CH2Cl2, 253 K). The frozen-solution (77 K) EPR spectrum of electrogenerated Ni(txn)3 is compatible with the d(z)2(1) ground state (g parallel-to, 2.083; g perpendicular-to components, 2.122 and 2.146). At ambient temperature Ni(txn)3- undergoes a facile spontaneous decomposition, affording the dimeric complex Ni2(SEt)2(CS3)2(2-). A rationale for this transformation is proposed. The structure of [Et4N]2[Ni2(SEt)2(CS3)2] is reported: a = 31.279 (9) angstrom, b = 13.670 (5) angstrom, c = 16.900 (4) angstrom, beta = 102.63 (2)-degrees, V = 7050 (4) angstrom 3, R = 0.0733, R(w) = 0.0720, space group C2/c, and Z = 8. In the dimeric anion, the metal atoms are thiolato bridged and one CS32- ligand is chelated to each metal center. The average Ni-S(chelate) and Ni-S(bridge) lengths are 2.173 (6) and 2.189 (5) angstrom, respectively; the Ni...Ni contact (d) is 2.767 (3) angstrom. The dihedral angle (alpha) between the two edge-sharing NiS4 planes is 111.1 (2)-degrees. In a group of complexes having this structural feature, d correlates linearly with sin (alpha/2).