Notes. Nuclear magnetic resonance evidence for three different isomers of [Ru 3 (µ-H)(µ-bzim)(CO) 9 (PPh 3 )](bzim = benzimidazolate). Crystal structure of [Ru 3 (µ-H)(µ-bzim)(CO) 10 ]·Me 2 CO

The reaction of [Ru3(CO)12] with benzimidazole (Hbzim) gave [Ru3(µ-H)(µ-bzim)(CO)10](la). The spectroscopic (fast atom bombardment mass, n.m.r., and i.r.) and analytical data were not enough to assign its structure unequivocally, which was suggested by its reactivity with PPh3{which led to a mixture of three isomers of [Ru3(µ-H)(µ-bzim)(CO)9(PPh3)], with the minor component (8%) having the PPh3 ligand on the Ru atom unbridged by the bzim moiety} and was confirmed by an X-ray structure determination of the acetone solvate. Crystals of (1a)·Me2CO are triclinic, space group P with Z= 2 in a unit cell of dimensions a= 12.995(9), b= 13.197(10), c= 7.708(12)Å, α= 92.47(3), β= 97.56(4), and γ= 91.94(3)°. The structure has been solved from diffractometer data by Patterson and Fourier methods and refined by full-matrix least squares to R= 0.0667 for 2 151 observed reflections. It comprises a triangle of Ru atoms in which the longest edge, 2.949(3)Å, is doubly bridged by a hydride and by a bzim ligand bonded to the two Ru atoms through adjacent C arid N atoms of the imidazole moiety.