New Class of Ruthenium Sulfide Clusters: Ru4S6(PPh3)4, Ru5S6(PPh3)5, and Ru6S8(PPh3)6

Abstract
Reaction of RuCl2(PPh3)3 with S2- sources yields a family of phosphine-containing Ru−S clusters which have been characterized crystallographically and by MALDI-MS. Ru4S6(PPh3)4 (Ru−Ruav = 2.94 Å) has idealized Td symmetry whereas Ru6S8(PPh3)6 (Ru−Ruav = 2.82 Å) adopts the idealized Oh symmetry characteristic of Chevrel clusters. Ru5S6(PPh3)5 is formally derived by the addition of Ru(PPh3) to one face of Ru4S6(PPh3)4. In terms of its M−S connectivity, the Ru5S6 cluster resembles a fragment of the FeMo cluster in nitrogenase.