Syntheses and X-ray Crystal Structures of Di-and Trinuclear Trithiolate-Thioether-Bridged Complexes of Ruthenium. Electrochemistry of Mixed-Valence Triruthenium Complexes

摘要

The reaction of [(HMB)Ru~(II)(kappa~3SSS'-tpdt)] (1; HMB=eta~6-C_6Me_6; tpdt = S(CH_2CH_2S~-)_2) with 0.5 molar equiv of [CpRu~(III)Cl_2]_2 (2A; Cp =eta~5-C_5Me_5) at ambient temperature gives a mixture of products consisting of the dinuclear complex [{Ru~(III)(mu-lkappa~3SSS':2kappa~2SS-tpdt)Cl_2(CH_3-CN)}CpRu~(III)Cl] (6; 7%) and trinuclear complexes [{(HMB)Ru~(II)(mu_3-kappa3SSS':2kappaS:3kappaS-tpdt)}-(CpRu~(II)(mu-Cl)}_2] (7; 13%) and [{(HMB)Ru~(II)-1kappa~3SSS':2kappa~2SS-tpdt)}Ru~(III)Cl(mu-2kappa~3SSS':3kappa~2SS-tpdt){CpRu~(III)Cl}]Cl (8; 54%). 1 reacts with 1 molar (monomer) equiv of [Ru~(II)(COD)Cl_2L at 80degC to give yellow solids of [(HMB)Ru~(II)(mu-lkappa~3SSS':2kappa~2SS-tpdt)Ru~(II)(COD)Cl_2] (10) in 60% yield. [CpRu~(III)(kappa~3SSS'-tpdt)] (2) reacts with [Ru~(II)(COD)Cl_2]_n in refluxing acetonitrile or with (PPh_3)_3Ru~(II)Cl_2 in MeOH at room temperature to give the dark green trinuclear complex [{CpRu~(II)(mu--lkappa~3SSS':2kappa~2SS-tpdt)}_2Ru~(II)Cl]Cl (12) in high yield. Treatment of 8, 10, and 12 with NH_4PF_6 in acetonitrile results in facile replacement of one or two chloro ligands with solvent molecules, giving PF_6~- salts of the chloro-bridged species [{(HMB)Ru~(II)(mu-lkappa~3SSS': 2kappa~2SS-tpdt)}Ru~(II)(mu--2kappa~3SSS':3kappa~2SS-tpdt){CpRu~(II)(mu-Cl)}](PF_6)_2 (9), the bis(acetonitrile) derivative [(HMB)Ru~(II)(mu-lkappa~3SSS':2kappa~2SS-tpdt)Ru~(II)(COD)(CH-3CN)_2](PF_6)_2 (11), and the mono-(acetonitrile) derivative [{CpRu~(II)(mu--1kappa~3SSS':2kappa~2SS-tpdt)}_2Ru~(II)(CH_3CN)](PF_6)_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 CH2C12. 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 mu_3-lkappa~3SSS':2kappaS: 3kappaS-bonding mode for the tpdt ligand.