Both α1- and α2-isomers of mono-Ru-substituted Dawson-type heteropolytungstates with a DMSO ligand, [α1-P2W17O61Ru(II)(DMSO)](8-) and [α2-P2W17O61Ru(II)(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-P2W17O61Ru(II)(DMSO)](8-) as a main product together with [α1-P2W17O61Ru(II)(DMSO)](8-), [PW11O39Ru(II)(DMSO)](5-), and [P2W18O62](6-) as byproducts. By addition of KCl to the reaction mixture, K8[α2-P2W17O61Ru(II)(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 [P2W17O61Ru(III)(H2O)](7-) (α1-isomer/α2-isomer ratio: ca. 8/1) as a main product together with [PW11O39Ru(III)(H2O)](4-) and [P2W18O62](6-) as byproducts. By addition of acetone to the reaction mixture, K7[P2W17O61Ru(III)(H2O)] is isolated in a good yield. Reaction of [P2W17O61Ru(III)(H2O)](7-) with DMSO produces [α1-P2W17O61Ru(III)(DMSO)](7-) as a main product and [α2-P2W17O61Ru(III)(DMSO)](7-) as a minor product. By addition of KCl and acetone, the α1-isomer K8[α1-P2W17O61Ru(II)(DMSO)] is isolated in a good yield. Both compounds are fully analyzed by CV, NMR ((1)H, (13)C, (31)P, and (183)W), IR, UV-vis, elemental analysis, mass spectroscopy, and single-crystal structure analysis. Assuming that isomerization does not occur during the reaction of [P2W17O61Ru(III)(H2O)](7-) with DMSO, the isolated [P2W17O61Ru(III)(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-P2W17O61Ru(II)(DMSO)](8-) and [α2-P2W17O61Ru(II)(DMSO)](8-) are compared together with Ru(DMSO)-substituted α-Keggin-type heteropolytungstates, [α-XW11O39Ru(DMSO)](n-) (X = Si, Ge, and P).

Both the α1- and the α2-isomers of mono-ruthenium (Ru)-substituted Dawson-type phosphotungstates with terminal aqua ligands, [α1-P2W17O61Ru(III)(H2O)](7-) (α1-RuH2O) and [α2-P2W17O61Ru(III)(H2O)](7-) (α2-RuH2O), were prepared in pure form by cleavage of the Ru-S bond of the corresponding DMSO derivatives, [α1-P2W17O61Ru(DMSO)](8-) (α1-RuDMSO) and [α2-P2W17O61Ru(DMSO)](8-) (α2-RuDMSO), respectively. Redox studies indicated that α1-RuH2O and α2-RuH2O show proton-coupled electron transfer (PCET), and the Ru(III)(H2O) species was reversibly reduced to Ru(II)(H2O) species and oxidized to Ru(IV)([double bond, length as m-dash]O) species and further to Ru(V)([double bond, length as m-dash]O) species in aqueous solution depending on the pH. Their redox potentials and thermal stabilities were compared with those of the corresponding α-Keggin-type derivatives ([α-XW11O39Ru(H2O)](n-); X = Si(4+) (n = 5), Ge(4+) (n = 5), or P(5+) (n = 4)). The basic electronic and redox features of Ru(L)-substituted Keggin- and Dawson-type heteropolytungstates (with L = H2O or O(2-)) were analyzed by means of density functional calculations. Similar to the corresponding α-Keggin-type derivatives, both α1-RuH2O and α2-RuH2O show catalytic activity for water oxidation.

In our previous article (Dalton Trans. 2008, 6692–6698) we reported that hydrothermal reaction of a mono‐lacunary Keggin‐type silicotungstate, [SiW11O39]8–, and Ru(acac)3 (acac: acetylacetonate) for 5–24 h produced a mono‐Ru‐substituted Keggin‐type silicotungstate with a terminal aqua ligand, [SiW11O39RuIII(H2O)]5–, which was further converted into a carbonyl (CO) derivative, [SiW11O39RuII(CO)]6–, by increasing the reaction time for several days. Here, reactions of Ru(acac)3 with other mono‐lacunary heteropolytungstates for the formation of other mono‐Ru(CO)‐substituted heteropolytungstates, including Keggin derivatives, [GeW11O39RuII(CO)]6– and [PW11O39RuII(CO)]5–, and Dawson‐type phosphotungstates, [α1‐P2W17O61RuII(CO)]8– and [α2‐P2W17O61RuII(CO)]8–, are presented. The desired α2‐isomer of Dawson‐type phosphotungstate, [α2‐P2W17O61RuII(CO)]8–, was produced in high purity and was fully characterized by CV, 31P NMR, 13C NMR, IR, UV/Vis, elemental analysis, mass spectroscopy, TG‐DTA, TPD‐MS, and single‐crystal structure analysis. On the other hand, Keggin‐type complexes, [GeW11O39RuII(CO)]6– and [PW11O39RuII(CO)]5–, were formed together with their aqua derivatives, [GeW11O39RuIII(H2O)]5– and [PW11O39RuIII(H2O)]4–, respectively, and the α1‐isomer of Dawson‐type phosphotungstate, [α1‐P2W17O61RuII(CO)]8–, was produced together with the α2‐derivative, as confirmed by CV, IR, mass spectroscopy, and 31P NMR spectroscopy.

Preparation and Structural Characterization of Mono-Ru-Substituted  2-Dawson-Type Phosphotungstate with a Carbonyl Ligand and Other Ru(CO)--Substituted Heteropolytungstates. -The  2-isomer (IV) is characterized by single crystal XRD, IR, ESI-MS, cyclic voltammetry, and NMR spectroscopy. It crystallizes in the trigonal space group R3 with Z = 3. Analogous reactions of (II) with [ 1-P2W17O61] 10-, [PW11O39] 7-, and [GeW11O39] 8-(H2O, 170 C, autoclave, 4 d) produce mono-Ru(CO)-substituted heteropolytungstates [ 1-P2W17O61Ru(CO)] 8-, [PW11O39Ru(CO)] 5-, and [GeW11O39Ru(CO)] 6-, respectively. -(NISHIKI, K.; OTA, H.; OGO, S.; SANO, T.; SADAKANE*, M.; Eur. J. Inorg. Chem. 2015, 16, 2714-N2723, http://dx.doi.org/10.1002/ejic.201500226 ; Dep. Appl. Chem., Grad. Sch. Eng., Hiroshima Univ., Higashi-Hiroshima 739, Japan; Eng.) -W. Pewestorf