Chemistry of polynuclear metal complexes with bridging carbene or carbyne ligands. Part 62. Synthesis of penta-, hexa-, and hepta-heteronuclear metal cluster compounds involving tungsten or molybdenum with platinum or nickel: crystal structures of the chain compounds [Pt3W3(µ-CMe)(µ3-CMe)2(CO)6(cod)(η-C5Me5)3]·0.5CH2Cl2 and [Pt3W4(µ-CC6H4Me-4)2(µ3-CC6H4Me-4)2(CO)8(η-C5H5)4]
Abstract
Addition of [Pt(cod)2](cod = cyclo-octa-1,5-diene), in tetrahydrofuran (thf) saturated with ethylene, to the compound [Pt2W3(µ-CMe)2(µ3-CMe)(CO)6(η-C5Me5)3] affords the hexanuclear metal complex [Pt3W3(µ-CMe)(µ3-CMe)2(CO)6(cod)(η-C5Me5)3]. A related compound [Pt3Mo2W(µ-CMe)(µ3-CC6H4Me-4)2(CO)6(cod)(η-C5H5)3] can be prepared by displacing a cod ligand from [Pt3Mo2(µ3-CC6H4Me-4)2(CO)4(cod)2(η-C5H5)2] with [W(![[triple bond, length half m-dash]](https://www.rsc.org/images/entities/char_e007.gif)
CMe)(CO)2(η-C5H5)]. The triplatinumdimolybdenum complex required for this synthesis was obtained from the reaction between excess [Pt(cod)2] and [PtMo2(µ-CC6H4Me-4)2(CO)4(η-C5H5)2]. Several heptanuclear mixed-metal compounds have been prepared. Thus the hexanuclear metal compound [Pt3W3(µ-CMe)(µ3-CMe)2(CO)6(cod)(η-C5Me5)3] reacts with [W(CMe)(CO)2(η-C5H5)] to afford [Pt3W4(µ-CMe)2(µ3-CMe)2(CO)8(η-C5H5)(η-C5Me5)3], while the pentanuclear metal compound [Pt3W2(µ3-CC6H4Me-4)2(CO)4(cod)2(η-C5H5)2] with an excess of [W(CC6H4Me-4)(CO)2(η-C5H5)] yields [Pt3W4(µ-CC6H4Me-4)2(µ3-CC6H4Me-4)2(CO)8(η-C5H5)4]. Similarly, [Pt3W4(µ-CMe)2(µ3-CMe)2(CO)8(η-C5Me5)4] is obtained from the reaction between [Pt3W3(µ-CMe)(µ3-CMe)2(CO)6(cod)(η-C5Me5)3] and [W(CMe)(CO)2(η-C5Me5)]. Complexes containing chains of seven metal atoms incorporating nickel in place of platinum, or molybdenum for a site which could be occupied by tungsten, have also been prepared. These include [Ni3W4(µ-CMe)2(µ3-CMe)2(CO)8(η-C5Me5)4], [NiPt2W4(µ-CMe)2(µ3-CMe)2(CO)8(η-C5Me5)4], [Pt3Mo2W2(µ-CMe)2(µ3-CC6H4Me-4)2(CO)8(η-C5H5)4], and [Pt3Mo2W2(µ-CC6H4Me-4)2(µ3-CC6H4Me-4)2(CO)8(η-C5H5)2(η-C5Me5)2]. Several of the hexa- and hepta-nuclear metal compounds are formed as mixtures of diastereoisomers which in some cases can be separated, or partially separated, by column chromatography. The isomerism results from different conformations of the metal chains, and is revealed by the n.m.r. data (1H, 13C-{1H}, and 195Pt-{1H}), which are reported and discussed. X-Ray diffraction studies were carried out on [Pt3W3(µ-CMe)(µ3-CMe)2(CO)6(cod)(η-C5Me5)3] and [Pt3W4(µ-CC6H4Me-4)2(µ3-CC6H4Me-4)2(CO)8(η-C5H5)4], the former crystallising with a molecule of CH2Cl2 in the unit cell. The X-ray results establish the conformations of particular diastereoisomers of these species, and place the stepwise cluster-building reactions described herein on a firm structural foundation.
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