Homo- and hetero-bimetallic B-frame compounds: some novel twelve-vertex Ru/Ru, Os/Os, Ru/Os, and Os/Ru metallaboranes

Abstract

The close-type eleven-vertex metallaboranes [PPh₃)₂RuB₁₀H₈(OEt)₂] and [(PMe₂Ph)₂OsB₁₀H₈(OEt)₂] readily react with a second metal centre [M′Cl₂(PPh₃)₃](M′= Ru or Os) to yield the novel mixed-valance bimetallic species [(PPh₃)₂ClM′ClM(PR₃)B₁₀H₈(OEt)₂] in which the second metal centre is bound exopolyhedrally to the original cluster in a remarkable way by converting two terminal B–H_t groups into two electron M′–H_µ–B links and involving one terminal M′–Cl group in a third link to the cluster via a four-electron M′–Cl–M bridge; the original cluster metal M remains a sixteen-electron centre but can be readily converted into an eighteen-electron one by replacement of phosphine ligand by bidentate chelates such as CH₂(PPh₂)₂(dppm).