A high-pressure infrared study of the stability of some ruthenium and osmium clusters to CO and H2 under pressure

Abstract

A high-pressure i.r. study has been made of the stability of some high-nuclearity carbonyl clusters of ruthenium and osmium to carbon monoxide and hydrogen, and of the thermal stabilities of these clusters under an inert atmosphere. In solution, the hexanuclear cluster [Os₆(CO)₁₈] reacts with CO (90 atm, 160 °C, 1 h) to produce the new pentanuclear cluster [Os₅(CO)₁₉] and [Os(CO)₅]. In contrast, in the solid state [Os₆(CO)₁₈] adds 2 mol of CO to form [Os₆(CO)₂₀]. The pentanuclear carbonyl [Os₅(CO)₁₉] undergoes reaction with CO to give both [Os₃(CO)₁₂] and [Os₂(CO)₉], and with [Os₂(CO)₉] to give [Os₇(CO)₂₁]. On heating in an inert atmosphere [Os₅(CO)₁₉] loses CO to generate [Os₅(CO)₁₆]. This reaction is reversible. Reaction of [Os₅(CO)₁₆], [Os₅H₂(CO)₁₆], [Os₆(CO)₁₈], or [Os₆H₂(CO)₁₈] with H₂ under moderate pressures and temperatures gives [OS₄H₄(CO)₁₂] and [OsH₂(CO)₄]; [Os₅(CO)₁₉] first produces [Os₅(CO)₁₆] and proceeds to the same products. On carbonylation under pressure [Ru₃(CO)₁₂] yields [Ru(CO)₅], and [Ru₆(CO)₁₇C] gives a mixture of [Ru₅(CO)₁₅C] and [Ru(CO)₅]. Pyrolysis of [Ru₆H₂(CO)₁₈] under argon at 120 °C gives the hexanuclear carbide [Ru₆(CO)₁₇C] in high yield.