Square Planar versus Tetrahedral NiS4 Cores in the Coordination Spheres of (HMB)Ru(II) and CpRu(III) and a Related CuS4 Complex. Synthetic, Single-Crystal X-ray Diffraction, and Magnetic Studies {HMB = η6-C6Me6 and Cp = η5-C5Me5}

The reaction of [LRu(κ3 SSS ‘-tpdt)] (L = η6-C6Me6 (HMB), (1); L = η5-C5Me5 (Cp*), (2); tpdt = S(CH2CH2S-)2) with Cl2Ni(PPh3)2 gave diamagnetic trinuclear complexes, [{(HMB)RuII(μ-1κ3 SSS ‘:2κ2 SS-tpdt)}2NiII]2+ (3) and [{Cp*RuIII(μ-1κ3 SSS ‘:2κ2 SS-tpdt)}2NiII]2+ (4), isolated as hexafluorophosphate salts in 96 and 61% yields, respectively. A similar reaction of 2 with CuSO4 in excess gave a dinuclear species, [Cp*RuIII(μ-1κ3 SSS ‘:2κ2 SS-tpdt)CuII-(CH3CN)2]2+ (5) (73% yield, as PF6 - salt), which further reacted with 1 molar equiv of 2 to give a paramagnetic complex, [{Cp*RuIII(μ-1κ3 SSS ‘:2κ2 SS-tpdt)}2CuII]2+ (6) (81% yield, as PF6 - salt), or 1 molar equiv of 1 to give the “mixed-ring” tpdt dithiolate-bridged diamagnetic complex [{Cp*RuIII(μ-1κ3 SSS ‘:2κ2 SS-tpdt)}CuII{(HMB)RuII(μ-1κ3 SSS ‘:2κ2 S S-tpdt}]2+ (7) (89% yield, as PF6 - salt). The molecular structures of complexes 3−7 were determined by single-crystal X-ray diffraction analysis. Notably it was observed that the trimetallic array Ru−M−Ru possesses a M−M bond between the central metal atom (Ni(II) or Cu(II)) and terminal Ru atoms in +3 oxidation state, i.e., Ru atoms bearing a Cp* ligand. Thus, while Ni is in a square planar environment in 3, in the other trinuclear complexes, viz., 4, 6, and 7, Ni/Cu is in a slightly distorted tetrahedral environment with respect to the four thiolate S donors, but is formally five- or six-coordinate, in the presence of one or two M−M bonds, respectively. Variable-temperature magnetic susceptibility studies on neat powders of representative compounds 2, 3, 4, and 6 show S = 1/2 Curie-like behavior for mononuclear Ru(III) complex 2, as expected, and also for the trinuclear {Ru(III)Cu(II)Ru(III)} complex 6, the behavior of the latter being ascribed either to a 19e electron count on Cu, involving Ru−Cu bonding, or to a strongly antiferromagnetically coupled {Ru(III)(S = 1/2)Cu(II)(S = 1/2)Ru(III)(S = 1/2)} sulfur-bridged moiety. Complexes 3 and 4, having oxidation states Ru(II)Ni(II)Ru(II) and Ru(III)Ni(II)Ru(III), respectively, are close to being diamagnetic but display very weak paramagnetism between 4.2 and 300 K.