Chemistry of di-and tri-metal complexes with bridging carbene or carbyne ligands. Part 38. Ruthenium–tungsten compounds: crystal structures of [RuW-(µ-Cl)(µ-CMe)(Cl)(CO)2(PPh3)2(η-C5H5)] and [RuW2(µ3-C2Me2)(CO)7(η-C5H5)2]

Purple crystals of the compound [RuW(µ-Cl)(µ-CMe)(Cl)(CO)2(PPh3)2(η-C5H5)] are obtained by placing a diethyl ether solution of [W(CMe)(CO)2(η-C5H5)] above a tetrahydrofuran (thf) solution of [RuCl2(PPh3)3]. The ruthenium–tungsten complex has been characterised by an X-ray diffraction study. The Ru–W bond [2.769(1)A] is spanned by the Cl and CMe ligands [C–W 1.942(11), C–Ru 2.021(9), Ru–Cl 2.447(3), W–Cl 2.497(3)A]. In addition to the cyclopentadienyl ligand the W atom carries terminal Cl and CO ligands which exhibit a positional disorder between two effectively interchangeable sites in the complementary ratios 3: 1. The ruthenium atom is ligated by two PPh3 groups and a CO group. Treatment of the ruthenium–tungsten complex with MeCCMe affords [RuW(µ-Cl)(µ-CMe)(Cl)(CO)2(PPh3)(η-C2Me2)(η-C5H5)], possible structures for which are discussed on the basis of n.m.r. data. The compound [W(CMe)(CO)2(η-C5H5)] reacts with the species [Ru(CO)n(PPh3)5–n](n= 2 or 3) to afford an insoluble trimetal complex [RuW2(µ3-C2 Me2)(CO)6(PPh3)(η-C5H5)2]. The PPh3 group in the latter may be displaced with CO or PEt3 to give the species [RuW2(µ3-C2Me2)(CO)6(L)(η-C5H5)2](L = CO or PEt3), but the reaction with CO is reversed unless the PPh3 is removed by complexation. The structure of the heptacarbonyl complex has been established by X-ray diffraction. The molecule has a triangular metal core [Ru–W 3.026(1) and 2.835(1), W–W 2.944(1)A] bridged by the MeCCMe ligand in such a manner that the alkyne lies essentially parallel to one of the Ru–W vectors. Hence this ligand is σ bonded to the ruthenium atom and to one tungsten centre [C–RU 2.068(9), C–W 2.169(9)A] while being η2 co-cordinated to the other tungsten atom [C–W mean 2.281 (9)A]. The ruthenium atom carries three terminally bound CO ligands, while the tungsten atoms are each ligated by a C5H5 and two CO groups. Three of the four CO ligands bound to tungsten semi-bridge the edges of the metal–atom triangle. The complexes [RuW2(µ3-C2Me2)(CO)6(L)(η-C5H5)2] undergo dynamic behaviour in solution, as revealed by n.m.r. studies.