Reactivity of unsaturated hydrides of osmium and ruthenium

The purpose of this work has been to study the reactivity of coordinatively unsaturated transition metal hydrides of the class MHX(CO)L₂ (M = Ru, Os; X = halide, L = bulky tertiary phosphine) toward a variety of inorganic and organic reagents. Using NMR, IR spectroscopy, and visual observations, it has been established that MHX(CO)L₂ can react in the solid state with a variety of gaseous reagents under much milder conditions than those previously reported, many types of reactions are possible (adduct formation, oxidative addition, insertion).; The reaction of MHCl(CO)L₂ (L = PiPr₃ ; M = Ru or Os) with a number of terminal alkynes has been studied at variable temperatures and for a variety of R groups representing a wide range of steric and electronic effects. This reveals the formation of an η 2-alkyne adduct, then hydrido-vinylidene, and finally the η1-vinyl complex. The rate of the formation of vinyl decreases with R according to primary > tertiary > secondary and electron withdrawing > electron donating. The results of mechanistic studies are consistent with the mechanism of vinyl complex formation involving the direct alkyne attack cis to the hydride.; The study of the insertion of olefins into M-H bond has revealed that: (1) the Os complex favors unsaturated π-bonded ligands and an 18-electron count while Ru favors saturated ligands and an unsaturated metal center; (2) the weaker π bond in the alkyne than in the alkene makes insertion or isomerization of an alkyne thermodynamically more favored than that of an alkene.; The study of the phosphine influence on the synthesis and the reactivity of RuHX(CO)L₂ has shown that the less bulky PiPr ₂Me leads to binding of three phosphines to Ru, and, in the case of RuCl₂(CO)L₂, to dimerization. The loss of the phosphine is observed in reactions with alkynes. In comparison to PiPr ₃ analog, the complex with L = PiPr₂(3,5(CF ₃)₂C₆H₃) is more Lewis acidic towards chloride.; The reactions of MHCl(CO)L₂ towards NO lead to the formation of the adduct, a persistent ligand-centered radical, characterized by EPR and IR spectroscopy, followed by the formation of unusual hydrido-nitrosyl and nitrosyl complexes.