Chemistry of polynuclear metal complexes with bridging carbene or carbyne ligands. Part 85. Synthesis of chain and ring compounds containing molybdenum

Abstract

Reactions between [Mo(CC6H4Me-4)(CO)2(η-C5H5)] and [M(cod)2](M = Ni or Pt, cod = cyclo-octa-1,5-diene) in light petroleum afford the trimetal compounds [MMo2(µ-CC6H4Me-4)2(CO)4(η-C5H5)2]. The latter with 1 equivalent of [Pt(cod)2] in thf (tetrahydrofuran) give the tetranuclear metal compounds [MPtMo2(µ-CC6H4Me-4)(µ3-CC6H4Me-4)(CO)4(cod)(η-C5H5)2], while [NiMo2(µ-CC6H4Me-4)2(CO)4(η-C5H5)2] with two equivalents of [Pt(cod)2] yields the pentanuclear metal complex [NiPt2Mo2(µ3-CC6H4Me-4)2(CO)4(cod)2(η-C5H5)2]. The cod ligands in the latter may be replaced with [W(CPh)(CO)2(η-C5H5)] to afford the heptanuclear metal compound [NiPt2Mo2W2(µ-CPh)2(µ3-CC6H4Me-4)2(CO)8(η-C5H5)4]. The reagents [PtW{µ-C(R)CO}(CO)(PMe3)(cod)(η-C5H5)](R = Ph or C6H4Me-4) have been used to prepare the trimetal complexes [PtM′M″(µ-CR)(µ-CR′)(CO)4(η-C5H5)2](M′= M″= W, R = C6H4Me-4, R′= Me; M′= W, M″= Mo, R = R′= C6H4Me-4; M′= W, M″= MO, R = Ph, R′= C6H4Me-4) and [PtMoW(µ-CMe)(µ-CC6H4Me-4)(CO)4(η-C5H5)(η-C5Me5)]. The reaction between [PtMo2(µ-CC6H4Me-4)2(CO)4(η-C5H5)2] and an excess of [Ni(cod)2] yields the octanuclear metal complex [Ni2Pt2Mo4(µ-CC6H4Me-4)(µ3-CC6H4Me-4)3(µ-CO)(CO)7(η-C5H5)4], formed as a mixture of two isomers. In one isomer a p-tolylmethylidyne ligand edge-bridges a Mo–Ni bond, and in the other a Mo–Pt bond. At reflux temperatures in thf the two isomers are converted into the symmetrical species [Ni2Pt2Mo4(µ3-CC6H4Me-4)4(CO)8(η-C5H5)4] in which all four alkylidyne ligands occupy triply bridging sites. Complicated isomeric mixtures of octanuclear metal clusters, with one edge-bridging and three triply bridging alkylidyne ligands, have been obtained from reactions between the complexes [PtM′M″(µ-CR)(µ-CR′)(CO)4(η-C5H5)2] and [Ni(cod)2]. Refluxing these products in thf affords compounds [Ni2Pt2M′2W2(µ3-CR)2(µ3-CR′)2(CO)8(η-C5H5)4](M′= W, R = C6H4Me-4, R′= Me; M′= MO, R = Ph or C6H4Me-4, R′= C6H4Me-4) in which all four alkylidyne groups are triply bridging. However, two isomers exist for each species, and the nature of this isomerism is discussed. Different behaviour was observed on treatment of [PtMoW(µ-CMe)(µ-CC6H4Me-4)(CO)4(η-C5H5)(η-C5Me5)] with [Ni(cod)2]. The major product was the heptanuclear metal chain cluster [NiPt2Mo2W2(µ-CMe)2(µ3-CC6H4Me-4)2(CO)8(η-C5H5)2(η-C5Me5)2]. The new compounds have been characterised by n.m.r. spectroscopy (1H, 13C-{1H}, and 195Pt-{1H} for those species containing platinum).