Solid state structure and fluxionality in solution of [H4Ru4(CO)11L] (L=P(C6F5)3, PMe2Ph, P(OMe)3 and P(OEt)3): two different structures

The monosubstituted [H4Ru4(CO)11L] derivatives where L=P(C6F5)3, PMe2Ph, P(OMe)3 and P(OEt)3 (compounds 1 to 4, respectively) were synthesized, the crystal structure of 1, 2 and 4 were determined by X-ray diffraction (that of compound 3 had been determined previously but not fully reported so we obtained it again) and their dynamical behavior studied by 1H, 31P and 19F NMR. The structures of compounds 1, 3 and 4 show the common tetrahedral structure with four long (hydride bridged) and two short metal–metal bonds with the P-donor ligand transoid to an unbridged Ru–Ru bond. The structure of 2 is different since the M–M bonds to the Ru atom bonded to the phosphine, are all hydride-bridged. The variable temperature NMR studies of 1, 2 and 3 show dynamical behaviour similar to what had been reported for compound 4. However we propose that some of the structures involved in the equilibrium have the phosphorus substituent transoid to a bridged Ru–Ru bond. [Copyright &y& Elsevier]