Chemistry of polynuclear metal complexes with bridging carbene or carbyne ligands. Part 49. Synthesis of mixed-metal complexes with bonds between Cr, Mo or W and Co, Rh, Ir or Re; crystal structure of [CrReRh2(µ3CC6H4Me-4)-(µ-CO)(CO)9(η-C9H7)2]

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Abstract
Treatment of the compounds [ReM(CR)(CO)9](M = Cr or W, R = C6H4Me-4) with one equivalent of [Rh(CO)2(η-C9H7)] in light petroleum or tetrahydrofuran (thf) affords the trimetal complexes [MReRh(µ-CR)(CO)10(η-C9H7)]. The latter, in refluxing thf, release CO and yield the trimetallatetrahedrane clusters [MReRh(µ3-CR)(CO)9(η-C9H7)]. Reactions between [Rh(CO)2(η-C9H7)] and [MReRh(µ-CR)(CO)10(η-C9H7)] give the compounds [MReRh2(µ3-CR)(µ-CO)(CO)9(η-C9H7)2]. The molecular structure of the tetranuclear metal cluster containing chromium has been established by X-ray diffraction. A CrRh2 triangle of metal atoms [Cr–Rh 2.713(l) and 2.720(2), Rh–Rh 2.659( 1)Å] is essentially symmetrically capped by the p-tolylmethylidyne ligand [µ3-C–Cr 1.910(7), mean µ3-C-Rh 2.044 Å]. The Rh–Rh bond is symmetrically bridged by a CO ligand, and each rhodium carries a η-C9H7 group. The chromium atom, in addition to being part of the µ3-CCrRh2 fragment, is ligated by an Re(CO)5 moiety and four CO groups, two of which weakly semibridge the Cr–Rh bonds. The cobalt–tungsten complexes [CoW(CR)(CO)8](R = Me or C6H4Me-4) with [ Rh (CO)2(η-C9H7)] in light petroleum yield the cobaltdirhodium compounds [CoRh2(µ3-CR)(µ-CO)(CO)3(µ-C9H7)2]. Structurally related [CoRh2(µ3-CC6H4Me-4)(µ-CO)(CO)3-(η-C5Me5)2] has been obtained from [CoW(CC6H4Me-4)(CO)8] and [Rh2(µ-CO)2(η-C5Me5)2]. Similar syntheses using [MoW(CR)(CO)7(η-C5H5)](R = C6H4Me-4) with [Co2(CO)8] or [Rh(CO)2(η-C9H7)] afford [MoCo2(µ3-CR)(CO)8(η-C5H5)], and a mixture of the di- and tri-metal compounds [MoRh(µ-CR)(CO)3(η-C5H5)(η-C9H7)] and [MoRh2(µ3-CR)(µ-CO)(CO)2(η-C5H5)(η-C9H7)2], respectively. Related p-tolylmethylidyne bridged complexes [MoM (µ-CR)(CO)2(L)(η-C5H5)(η-C9H7)](M = Rh, L = PMe3; M = Ir, L = CO), [WM(µ-CR)(CO)3(η-C5Me5)(η-C9H7)](M = Rh or Ir), [WRh2(µ3-CR)(µ-CO)2(CO)2(η-C5Me5)(η-C9H7)2], and [WRhIr(µ3-CR)(µ-CO)-(CO)2(η-C5H5)(η-C9H7)2] have also been synthesised. Spectroscopic data for the new compounds are reported, and are discussed in relation to the structures proposed.

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