Mechanistic study of the reaction of Os3(CO)10(CNPr)(NCMe) with Brønsted acid

The reaction of Os3(CO)10(CNPr)(NCMe) (1) with Brønsted acid in CH2Cl2 takes place initially via the protonation of 1 to yield the hydrido complex [(μ-H)Os3(CO)10(CNPr)(NCMe)]+ (2), followed by substitution of labile acetonitrile ligand with carboxylate anion to form the monodentate carboxylate complexes (μ-H)Os3(CO)10(CNPr)(η1-OCOR) (3). Spectroscopic and crystallographic evidence is presented to explain mechanistic details of the reaction. Molecular structures of (μ-H)Os3(CO)10(CNPr)(η1-OCOCF3) (3a) and (μ-H)Os3(CO)10(CNPr)(η1-OCOC CH) (3b) have been determined by X-ray diffraction studies. Crystal data: 3a: P21; a = 11.6632(19), b = 14.7827(24), c = 14.487(3) Å; β = 103.635(15)°, V = 2427.4(7) Å3, Z = 4, R = 5.2%, Rw = 5.4%. 3b: P32; a = 14.853(3), c = 9.158(3) Å; V= 1749.6(7) Å3, Z = 3, R = 3.2%, Rw = 3.8%.