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Two vanadium(V)-substituted tungsto-polyoxometalate isomers, 1- and 4-[S2VW17O62](5-), were prepared as their tetra-alkyl ammonium salts from a W(VI)-H2SO4-V(V) reaction mixture in aqueous CH3CN solution. X-ray crystallographic structural analysis revealed that both isomers have a Wells-Dawson-type structure with a higher occupancy of vanadium at polar sites and belt sites for 1- and 4-[S2VW17O62](5-), respectively. The isomers were also characterized by elemental analysis, infrared, Raman, UV-vis, and (51)V NMR spectroscopies as well as voltammetry, and the data obtained were compared with that derived from [S2W18O62](4-). Significantly, the reversible potentials for the vanadium(V/IV) couple for both 1- and 4-[S2VW17O62](5-) in CH3CN (0.1 M n-Bu4NPF6) are considerably more positive than the tungstate reduction process exhibited by the [S2W18O62](4-) framework, implying that the presence of vanadium should be useful in catalytic reactions. The one-electron-reduced [S2V(IV)W17O62](6-) forms of both isomers were prepared in solution by controlled potential bulk electrolysis and characterized by voltammetry and EPR spectroscopy.

A tetranuclear cobalt(III) complex with the cubane Co4O4 core, [Co4(pg)4(μ3-O)4] (Hpg: N-(2-pyridylmethyl)glycine), was prepared and the structure was determined by the X-ray diffraction method. This complex has the four N–H···O intramolecular hydrogen-bonds between the amino group on one of the four cobalt atoms and the carboxyl group on another cobalt atom. Its neutral aqueous solution showed no spectral change for at least 3 days.

Reaction of cis-Pt(C⋮CTp)2(dppe) (Tp = thiophene) with Ru3(CO)11(CH3CN) in refluxing toluene for 1 h resulted in head-to-head C−C bond coupling of the alkynyl ligands forming 1,4-bis(3-thiophenyl)buta-1,3-diyne, which afforded an extraordinal 1,4-heterodimetalla[5,6-b]thienopentalene, [PtRu3{μ4-η1:η1:η1:η1:η4:η4-C4H2S-CCC(H)CTp}(μ-CO)2(CO)6(dppe)] (1) (Tp = 3-thiophene), in 54% yield. Its crystal structure shows that a hydrogen shift occurs from the thiophene substituent to an end carbon atom of the 1,3-diyne, transforming 1,4-bis(3-thiophenyl)buta-1,3-diene, which results in formations of PtC4 and RuC4 rings, both with metallacyclopenta-2,4-diene. The Ru3(μ-CO)2(CO)6 moiety conforms to an open cluster, and its central ruthenium atom forms a RuCp ring whose carbon atoms bond to two ruthenium atoms by eight Ru−C π-bonds. Reactions of the acetylides with single metal media, Fe(CO)5, gave rise to annealation of alkynyls via both cyclic and acyclic dimerization processes, affording extraordinal metallacycles of 1,3-diyne, a platinacyclobutene consisting of a cyclone, [FePt{μ2-η1:η1:η4-(C4Tp2-CO)-CO}(CO)3(dppe)] (2), and a 1,2-heterodimetallacyclo-3-penten-5-one, [FePt(μ2-η1:η1:η2-TpCCCCTp-CO)(μ-CO)(CO)2](dppe)] (3), in 15 and 16% yields, respectively.