Preparation and Redox Studies of α1- and α2‑Isomers of Mono-Ru-Substituted Dawson-type Phosphotungstates with a DMSO Ligand: [α1/α2‑P2W17O61RuII(DMSO)]8–

Both α1- and α2-isomers of mono-Ru-substituted Dawson-type heteropolytungstates with a DMSO ligand, [α1-P2W17O61RuII(DMSO)]8– and [α2-P2W17O61RuII(DMSO)]8–, are prepared from the α2-isomer of a monolacunary derivative, [α2-P2W17O61]10–. Reaction of [α2-P2W17O61]10– with Ru­(DMSO)4Cl2 under hydrothermal conditions produces [α2-P2W17O61RuII(DMSO)]8– as a main product together with [α1-P2W17O61RuII(DMSO)]8–, [PW11O39RuII(DMSO)]5–, and [P2W18O62]6– as byproducts. By addition of KCl to the reaction mixture, K8[α2-P2W17O61RuII(DMSO)] is isolated in a moderate yield. On the other hand, reaction of [α2-P2W17O61]10– with Ru2(benzene)2Cl4 under hydrothermal conditions produces an isomeric mixture of [P2W17O61RuIII(H2O)]7– (α1-isomer/α2-isomer ratio: ca. 8/1) as a main product together with [PW11O39RuIII(H2O)]4– and [P2W18O62]6– as byproducts. By addition of acetone to the reaction mixture, K7[P2W17O61RuIII(H2O)] is isolated in a good yield. Reaction of [P2W17O61RuIII(H2O)]7– with DMSO produces [α1-P2W17O61RuIII(DMSO)]7– as a main product and [α2-P2W17O61RuIII(DMSO)]7– as a minor product. By addition of KCl and acetone, the α1-isomer K8[α1-P2W17O61RuII(DMSO)] is isolated in a good yield. Both compounds are fully analyzed by CV, NMR (1H, 13C, 31P, and 183W), IR, UV–vis, elemental analysis, mass spectroscopy, and single-crystal structure analysis. Assuming that isomerization does not occur during the reaction of [P2W17O61RuIII(H2O)]7– with DMSO, the isolated [P2W17O61RuIII(H2O)]7– contains the α1-isomer as a main compound with the α2-isomer as a minor compound. Unusual transformation of the α2-isomer of [P2W17O61]10– to the α1-isomer occurs. Redox behaviors of [α1-P2W17O61RuII(DMSO)]8– and [α2-P2W17O61RuII(DMSO)]8– are compared together with Ru­(DMSO)-substituted α-Keggin-type heteropolytungstates, [α-XW11O39Ru­(DMSO)]n− (X = Si, Ge, and P).