Triosmium–antimony clusters containing the μ,η2-phenylene ligand: Unusually long osmium–osmium bonds

The reaction of the osmium–antimony cluster Os3(μ-H)(μ-SbPh2)(μ3,η2-C6H4)(CO)9 with AsPh3 at room temperature afforded the o-phenylene cluster Os3(μ-H)(SbPh2)(μ2,η2-C6H4)(CO)9(AsPh3) by nucleophilic addition via a metal–metal bond cleavage, and the substitution product Os3(μ-H)(SbPh2)(μ3,η2-C6H4)(CO)8(AsPh3). It reacted with tBuNC to afford the adduct Os3(μ-H)(SbPh2)(μ2,η2-C6H4)(CO)9(CNtBu) quantitatively. This adduct isomerised slowly on standing via migration of the isonitrile, while photolysis led to decarbonylation to Os3(μ-H)(SbPh2)(μ2,η2-C6H4)(CO)8(CNtBu). All the products have been characterised completely, including by X-ray crystallography, and their structures exhibit very long Os–Os bonds.