Use of the monocationic fragment [Ru(η5-C5H5)(MeCN)3]+ as a capping reagent in the synthesis of mixed-metal clusters: synthesis and structural characterisation of [Os3RuH(CO)11(η5-C5H5)] and [Os3Ru2(CO)9(µ3-CO)2(η5-C5H5)2]

Abstract

The reaction of the monoanion [Os₃H(CO)₁₁]^– 1 with 1 equivalent of the cation [Ru(C₅H₅)(MeCN)₃]⁺ 2, in CH₂Cl₂, formed the mixed-metal, tetranuclear cluster [Os₃RuH(CO)₁₁(η⁵-C₅H₅)] 3 in high yield. Subsequent deprotonation of 3 with 1,8-diazabicyclo[5.4.0]undec-7-ene, in CH₂Cl₂, afforded the anion [Os₃Ru(CO)₁₁(η⁵-C₅H₅)]^– 4, and reaction of 4 with a second equivalent of [Ru(C₅H₅)(MeCN)₃]⁺ provided the new bis-(cyclopentadienyl) cluster [Os₃Ru₂(CO)₉(µ₃-CO)₂(η⁵-C₅H₅)₂] 5 in ca. 80% yield. Alternatively, reduction of [Os₃(CO)₁₂] with K/Ph₂CO afforded the known cluster dianion [Os₃(CO)₁₁]^2– 6 which can be treated with 2 equivalents of [Ru(C₅H₅)(MeCN)₃]⁺ to produce 5 in 75% yield. The clusters 3 and 5 have been fully characterised by both spectroscopic and crystallographic methods. The structure of 3 contains an Os₃Ru tetrahedron in which the cyclopentadienyl ligand is co-ordinated to the Ru atom in an η⁵ terminal mode. The metal framework in 5 is a trigonal bipyramid, but may be viewed as an Os₃Ru tetrahedral unit, as in 3, to which a second Ru atom capping an Os₂Ru triangular face has been added. Both the cyclopentadienyl ligands remain in η⁵ terminal bonding sites co-ordinated to the two Ru atoms.