Pentakis(methoxycarbonyl)cyclopentadiene chemistry. Part 7. Preparation and characterisation of some ruthenium complexes crystal and molecular structure of η-cyclopentadienyl[η-1,2,3,4,5-pentakis(methoxycarbonyl)cyclopentadienyl]ruthenium, [Ru(η-C5H5){η-C5(CO2Me)5}

Abstract

The salt Tl[C5(CO2Me)5] reacts with [RuCl(PPh3)2(η-C5H5)] in acetonitrile to give the complex [Ru(NCMe)(PPh3)2(η-C5H5)][C5(CO2Me)5]; in air the reaction affords [Ru(η-C5H5){η-C5(CO2Me)5}]. The crystal structure of the latter has been determined by single-crystal X-ray diffraction methods at 295 K, being refined to a residual of 0.026 for 6 438 ‘ observed ’ reflections. Crystals are triclinic, space group P, with a= 15.790(5), b= 8.968(4), c= 7.947(3)A, α= 67.52(3), β= 89.52(3), γ= 80.90(3)°, and Z= 2. Both ligands have an η5 relationship to the ruthenium in what is essentially an eclipsed sandwich compound. For the C5H5 ring, Ru–C is 2.178(2)–2.186(3)A, while for the C5(CO2Me)5 ligand, Ru–C is 2.157(2)–2.178(2)A; although these distances are uncorrected for libration, their relativity seems valid. The C5(CO2Me)5 ligand is displaced in reactions with tertiary phosphines in nitrite solvents, and this reaction forms the basis of a process for the oxidation of PPh3 catalysed by the metallocene. The protonation of [RuH(PPh3)2(η-C5H5)] by HC5(CO2Me)5 is also described.