Surface Mediated Organometallic Synthesis: Formation of [H~5Os~1~0(CO)~2~4]^- by Hydrogenation of Silica-Supported [Os(CO)~3(OH)~2]~n as a Springboard for a High-Yield Synthesis of [H~4Os~1~0(CO)~2~4]^2^- Starting from alpha-[Os(CO)~3Cl~2]~2 and Working in Ethylene Glycol Solution

Abstract

New high yield routes to the high nuclearity hydrido carbonyl clusters [H5Os10(CO)24]- and [H4Os10(CO)24]2-, model systems for the chemisorption of CO and H2 on metal surfaces, are reported. [H5Os10(CO)24]- is obtained in good yields by hydrogenation (1 atm) at 200°C of physisorbed [Os(CO)3(OH)2]n whereas in refluxing ethylene glycol solution, that is less acidic than the silica surface, [H4Os10(CO)24]2- is obtained in high yield starting from [Os(CO)3(OH)2]n or, more conveniently, from α-[Os(CO)3Cl2]2 in the presence of the stoichiometric amount of sodium carbonate. The quantitative equilibrium $$[{\text{H}}_{\text{4}} {\text{Os}}_{{\text{10}}} ({\text{CO}})_{24} ]^{2 - } \mathop {\underset { + {\text{H}}^{\text{ + }} } \leftrightarrows }\limits^{ + {\text{OH}}^ - } {\text{ }}[{\text{H}}_{\text{5}} {\text{Os}}_{{\text{10}}} ({\text{CO}})_{24} ]^ -$$ is confirmed.