Syntheses and x-ray crystal structures of di- and trinuclear trithiolate-thioether-bridged complexes of ruthenium. Electrochemistry of mixed-valence triruthenium complexes

Abstract

The reaction of [(HMB)RuII(κ3SSS′-tpdt)] (1; HMB = η6-C6Me6; tpdt = S(CH2CH2S-)2) with 0.5 molar equiv of [Cp*RuIIICl2]2 (2A; Cp* = η5-C5Me5) at ambient temperature gives a mixture of products consisting of the dinuclear complex [{RuIII(μ-1κ3SSS′:2κ2SS-tp dt) Cl2(CH3-CN)}Cp*RuIIICl] (6; 7%) and trinuclear complexes [{(HMB)RuII(μ3-1κ3SSS′:2κS :3κS-tpdt)}- {Cp*RuII(μ-Cl)}2] (7; 13%) and [{(HMB)RuII(μ-1κ3SSS′:2κ2S S-tpdt)} RuIIICl(μ-2κ3SSS′:3κ2SS-tp dt){Cp*RuIIICl}]Cl (8; 54%). 1 reacts with 1 molar (monomer) equiv of [RuII(COD)Cl2]n at 80°C to give yellow solids of [(HMB)RuII(μ-1κ3SSS′:2κ2 SS-tpdt)RuII(COD) Cl2] (10) in 60% yield. [Cp*RuIII(κ3SSS′-tpdt)] (2) reacts with [RuII(COD)Cl2]n in refluxing acetonitrile or with (PPh3)3RuIICl2 in MeOH at room temperature to give the dark green trinuclear complex [{Cp*RuIII(μ-1κ3SSS′: 2κ2SS-tpdt)}2RuIICl]Cl (12) in high yield. Treatment of 8, 10, and 12 with NH4PF6 in acetonitrile results in facile replacement of one or two chloro ligands with solvent molecules, giving PF6 - salts of the chloro-bridged species [{(HMB)RuII(μ-1κ3SSS′: 2κ2SS-tpdt)}RuIII(μ-2κ3 SSS′:3κ2SS-tpdt){Cp*RuIII(μ-Cl)}] (PF6)2 (9), the bis(acetonitrile) derivative [(HMB)RuII(μ-1κ3SSS′:2κ2 SS-tpdt)RuII(COD)(CH3CN)2] (PF6)2 (11), and the mono(acetonitrile) derivative [{Cp*RuIII(μ-1κ3SSS′: 2κ2SS-tpdt)}2RuII(CH3CN)] (PF6)2 (13), respectively. The triruthenium complexes can be electrochemically reduced and oxidized in one and sometimes two successive one-electron steps, with many of the reduced and oxidized species being stable on the cyclic voltammetric time scale at low temperatures (-40°C) in CH2Cl2. The location of the redox-active sites and the extent of delocalization in the species with unpaired electrons are discussed. The X-ray crystal structures of 6 and 7 and the PF6 - salts of 9, 11, and 13 are reported. The molecular structure of 7 exhibits a new μ3-1κ3SSS′:2κS: 3κS-bonding mode for the tpdt ligand.