Chemistry of di- and tri-metal complexes with bridging carbene or carbyne ligands. Part 47. Synthesis of tri-, tetra-, and penta-heteronuclear metal cluster compounds involving tungsten with platinum or nickel: crystal structures of the compounds [Pt3W2(µ3-CR)2(CO)4(cod)2(η-C5H5)2] and [Pt2W3(µ-CR)2(µ3-CR)(CO)6(η-C5H5)3](R = C6H4Me-4, cod = cyclo-octa-1,5-diene)

Abstract

Tris(ethylene)platinum, prepared in situ from [Pt(cod)2](cod = cyclo-octa-1,5-diene), reacts with the compounds [W(CR)(CO)2L] to give the complexes [PtW2(µ-CR)2(CO)4L2](R = Me or Ph, L =η-C5H5; R = Me, Ph, or C6H4Me-4, L =η-C5Me5). The analogous nickel compounds [NiW2(µ-CR)2(CO)4L2] have also been prepared using [Ni(cod)2]. Treatment of the trinuclear metal species [MW2(µ-CR)2(CO)4L2] with one equivalent of [Pt(cod)2] affords the tetranuclear metal compounds [MPtW2(µ-CR)(µ3-CR)(CO)4(cod)L2](M = Ni or Pt, R = C6H4Me-4, L =η-C5H5 or η-C5Me5; M = Pt, R = Me, L =η-C5Me5), while with two equivalents of [Pt(cod)2] the pentanuclear metal complexes [Pt3W2(µ3-CR)2(CO)4(cod)2L2](R = C6H4Me-4, L =η-C5H5; R = Me, L =η-C5Me5) are obtained. These tetra- and penta-nuclear metal compounds were generally isolated as isomeric mixtures, as revealed by n.m.r. measurements (1H, 13C-{1H}, and 195Pt-{1H}). An X-ray diffraction study structurally characterised a symmetrical isomer of [Pt3W2(µ3-CC6H4Me-4)2(CO)4(cod)2(η-C5H5)2], a molecule having a crystallographic two-fold rotation axis. The structure comprises two ‘butterfly’µ3-CPt2W fragments sharing a wing-tip platinum vertex, with isosceles metal triangles [Pt–W 2.751(1) and 2.748(1), Pt ⋯ Pt 3.089(1)A] capped by the CC6H4Me-4 groups. The terminal Pt atoms each carry a cod ligand, and the four CO groups semi-bridge Pt–W bonds. The pentanuclear metal compounds [Pt2W3(µ-CR)2(µ3-CR)(CO)6L3](R = C6H4Me-4, L =η-C5H5; R = Me or C6H4Me-4, L =η-C5Me5), [Pt2W3(µ-CMe)(µ-CC6H4Me-4)(µ3-CMe)(CO)6(η-C5H5)(η-C5Me5)2], and [Pt2W3(µ-CC6H4Me-4)2(µ3-CC6H4Me-4)(CO)6(η-C5H5)(η-C5Me5)2] have also been prepared by treating the appropriate tetranuclear metal compound [Pt2W2(µ-CR)(µ3-CR)(CO)4(cod)L2] with an alkylidynetungsten complex so as to displace the cod ligand. Again isomeric mixtures were produced, and identified by n.m.r. spectroscopy. An X-ray diffraction study established the molecular structure of one of the three isomers of [Pt2W3(µ-CC6H4Me-4)2(µ3-CC6H4Me-4)(CO)6(η-C5H5)3]. The molecule has an essentially planar five-metal atom framework, with two edge-bridging and one triply bridging tolylmethylidyne groups. Four of the six CO ligands semi-bridge W–Pt bonds [W–C–O 163–168(2)A] and each tungsten carries an η-C5H5 group, with each terminal W atom having one linearly bound CO. The Pt ⋯ Pt separation [2.949(2)A] implies little direct metal-metal bonding between these atoms. Bond lengths to the central µ3-CC6H4Me-4 ligand are µ3-C–Pt 2.02(3) and 2.09(2), µ3-C–W 1.99(3)A, while those to the edge-bridging CC6H4Me-4 groups are µ-C–W 1.96(2)(mean) and µ-C–Pt 2.03(2)A(mean).