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]

Abstract

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)Å] 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)Å]. 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)Å] 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)Å] while being η² co-cordinated to the other tungsten atom [C–W mean 2.281 (9)Å]. 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.