Chemistry of polynuclear metal complexes with bridging carbene or carbyne ligands. Part 95. Synthesis and crystal structures of [W2RuPt(µ-CC6H4Me-4)(µ3-CC6H4Me-4)(CO)6(PMe2Ph)(η-C5H5)2] and [W2Ru2Pt2(µ3-CC6H4Me-4)2(µ-CO)2(CO)9(η-C5H5)2]

Abstract

Treatment of [W₂Pt(µ-CC₆H₄Me-4)₂(CO)₄(η-C₅H₅)₂] in thf (tetrahydrofuran) with [Ru(CO)₄(η-C₂H₄)] in light petroleum affords the tetranuclear metal cluster compound [W₂RuPt(µ-CC₆H₄Me-4)-(µ₃-CC₆H₄Me-4)(CO)₇(η-C₅H₅)₂]. The latter with 1 equivalent of PMe₂Ph gives [W₂RuPt-(µ-CC₂H₄Me-4)(µ₃-CC₂H₄Me-4)(CO)₆(PMe₂Ph)(η-C₅H₅)₂], the structure of which has been established by X-ray diffraction. One p-tolylmethylidyne group caps three metal atoms WRuPt [W–Ru 2.743(1), W–Pt 2.729(1), and Ru–Pt 2.875(1)Å] in an essentially symmetrical manner. The ruthenium atom carries two carbonyl groups and the phosphine ligand [Ru–P 2.271(4)Å]. The tungsten atom is co-ordinated by a C₅H₅ ring and two CO ligands, but the latter asymmetrically bridge the W–Pt and W–Ru bonds [W–C–O 160(1) and 157(1)°, respectively]. The WRuPt triangle is linked through the Pt atom to a W(CC₆H₄Me-4)(CO)₂(η-C₅H₅) fragment via a W–Pt bond [2.733(1)Å] and a bridging µ-CC₆H₄Me-4 ligand [µ-C–W 1.92(1), µ-C–Pt 2.03(1)Å]. One of the CO groups attached to the W atom weakly semi-bridges the W–Pt bond [W–C–O 170(1)°]. The reaction between [Ru(CO)₄(η-C₂H₄)] and [W₂Pt₂(µ-CC₆H₄Me-4)(µ₃-CC₆H₄Me-4)(CO)₄(cod)^–(η-C₅H₅)₂](cod = cyclo-octa-1,5-diene) gives a hexanuclear metal cluster [W₂Ru₂Pt₂-(µ₃-CC₆H₄Me-4)₂(µ-CO)₂(CO)₉(η-C₅H₅)], the structure of which has also been determined by X-ray diffraction. For descriptive purposes, five of the metal atoms [W(2)Ru(1)Ru(2)Pt(1)Pt(2)] may be regarded as occupying vertices of a ‘trigonal bipyramid’ but one in which two of the metal–metal bonds [Pt(1)⋯ Pt(2) 3.064(4), Ru(1)⋯ Pt(2) 3.259(2)Å] are absent. Allowing for this, the ruthenium atoms occupy the apical sites, and the two platinum atoms and the tungsten atom occupy equatorial sites. The Pt(1) atom, in addition to being part of the open metal framework, is attached via a WPt bond [2.663(3)Å] to an external W(CO)₃(η-C₅H₅) fragment. One of the CO ligands on this W(1) atom asymmetrically bridges the W(1)Pt(1) linkage [W(I)–C–O 156(3), Pt(1)–C–O 122(2)°]. Both ruthenium atoms carry three terminal CO groups. The Pt(2) atom, ligated only by two of the metal atoms [W(2) and Ru(2)] in the framework, carries a terminal CO group, and the Pt(2)–Ru(2) bond is bridged by a CO ligand [Ru(2)–C–O 136(3), Pt(2)–C–O 143(4)°]. The W(2) atom carries a C₅H₅ ring. Both p-tolylmethylidyne groups occupy triply bridging sites. These are on the same side of the Pt(1)W(2)Pt(2) plane, one ligand caps the W(2)Ru(1)Pt(1) triangle, the other spans the atoms Pt(2), W(2), Ru(1). The n.m.r. spectra of the new mixed-metal clusters are reported and discussed.