Polyhedral phosphaborane chemistry: crystal and molecular structure of the diphenylphosphido-bridged arachno-decaboranyl cluster compound [PMePh3][6,9-µ-(PPh2)B10H12]

Abstract

[PMePh₃][B₁₀H₁₂(PPh₂)] crystallizes in the orthorhombic space group Pca2₁, with a= 3 316.9(4), b= 1 397.2(2), c= 1 469.6(1) pm, and Z= 8; the structure has been solved and refined to R= 0.0673, R′= 0.0743, for 4 104 independent reflections. The crystal contains two nearly identical [B₁₀H₁₂(PPh₂)]^–units in the unit cell. The ten-boron cage structure of the [B₁₀H₁₂(PPh₂)]^– anion resembles that of [B₁₀H₁₄]^2–, but it has a bridging PPh₂ group between the B(6) and B(9) positions instead of endo-terminal hydrides. The bonding about phosphorus is approximately tetrahedral with phosphorus-boron bond lengths averaging 189.5 pm. The unusual ‘remote’arachno 11-vertex structure is briefly discussed in comparison with some other isoelectronic arachno-type 11-vertex species.