Metallophilicity in annular Ru₂M₂ derivatives of (HMB)Ru^II(tpdt) versus (Bis)-η²-dithiolate bonding in Ru₂M derivatives of Cp*Ru^III(tpdt) (HMB = η⁶-C₆Me₆; Cp* = η⁵- C₅Me₅; M = Cu^I, Ag(I,II), Au (I,)

The reaction of [(HMB)Ru^II(η³-tpdt)] (1: HMB = η⁶-C₆Me₆; tpdt = S(CH₂CH ₂S^-)₂) with [Cu(MeCN)₄]PF ₆, AgPF₆, and (PPh₃)AuCl gave the annular species [{(HMB)Ru^II(μ₃-η¹: η¹:η³-tpdt)}₂(M)₂] ²⁺ [3: M = Cu^I; 3A: (M)₂ = Cu^I, Cu^I(MeCN); 4: M = Ag^I ; 6: M = Au^I], isolated as PF₆ salts in high yields. Complex 6 was formed in a reversible process with [{(HMB)-Ru^II(μ-η¹:η³- tpdt)}(AuPPh₃)]⁺ (5) involving dissociation/association of PPh₃. Similar reactions of [Cp*Ru^III(η³-tpdt)] (2: Cp* = η⁵-C₅Me₅) gave, respectively, the cationic metal-metal bonded Ru₂M complexes [{Cp*Ru(μ- η²:η³-tpdt)}₂M]ⁿ⁺ (7: M = Cu^I, n = 1; 8: M = Ag^II, n = 2) and [{Cp*Ru(μ- η¹:η³-tpdt)}(AuPPh₃)]⁺ (9), isolated as PF₆ salts in 71, 73, and 72% yields, respectively. In MeCN or THF for an extended period, 9 underwent transformation to a mixture of complexes, from which [{Cp*Ru}₂{μ-η⁶- (S(CH₂)₂S(CH₂)₂SAuPPh ₃)₂}]²⁺ (10), containing a μ-S₂ bridge, and [{Cp*Ru(μ-η¹:η¹: η³-tpdt)}(AuPPh₃)₂]⁺ (11) could be identified. The new complexes, 3-9 and 11, were all spectroscopically characterized, and the X-ray crystal structures of 3-10 have been determined. Cyclic voltammetry experiments were performed on compounds 3A, 4, and 6-8 at 233 K in CH₂Cl₂. 7 and 8 could be oxidized and reduced in several one-electron steps to form moderately stable species with extensive electron delocalization between the Ru₂M atoms. An EPR spectrum of 8, a Ag(II) (d⁹) species, was obtained at liquid He temperatures.