Reactivity of electron-poor decamethyl-1,3-diboraruthenocene with sulfur and phosphorus compounds

Decamethyl-1,3-diboraruthenocene [(η5-C5Me5)Ru{η5-(CMe)3(BMe)2}] (1) reacts with cyclo-octasulfur in hexane to give [(η5-C5Me5){η5-(CMe)3(BMe)2}RuS] (3), which may also be obtained from 1 and propylene sulfide. 1 reacts with H2S to form the ruthenathiacarboranyl complex [(η5-C5Me5)Ru{η4-(CMe)3(BMe)2S}] (6), for which a nido-structure is proposed. The isomeric compounds 3 and 6 have different stabilities: 3 loses sulfur and unexpectedly the closo-cluster [(η5-C5Me5)2Ru2H(CMe)3(BMe)2] (4) is formed with hydrogen bridging the basal and apical Ru centers. Reaction of 1 with carbonylsulfide (COS) yields the dinuclear ruthenium compound [(η5-C5Me5)Ru{η5-(CMe)3(BMe)2(S)(COBMe)}]2 (7) in which two B–O groups bridge two ruthenium complexes. Its formation results from a complex reaction sequence: sulfur inserts into the diborolyl ring and the ligand CO forms an oxygen–boron bridge to a second molecule, followed by insertion of the carbonyl carbon into the double bond of the diboraheterocycle. Carbon disulfide reacts with 1 to give the dinuclear complex 8 with two CS2 molecules connecting the ruthenium centers. When 1 and P4 are heated in toluene, the sandwich 9 is obtained by formal insertion of a P–H group into the diborolyl ring of 1 and the triple-decker [{η5-(C5Me5)Ru}2{μ-(MeC)3P(MeB)2} (10) is detected in the mass spectrum. The phosphaalkyne PCtBu inserts into 1 to give the ruthenaphosphacarborane [(η5-C5Me5)Ru{(CMe)2(BMe)(PCtBu)(CMe)(BMe)}] (11) in high yield. Phosphanes react with 1 to give weak donor–acceptor complexes 1 · PH2R (12) (R=Ph, H). The compositions of the compounds are deduced from spectroscopic and analytical data and are confirmed for 4 and 7 by X-ray structural analyses.