Eleven-vertex isocloso type rhodaundecaboranes: crystal structures and nuclear magnetic resonance properties of [(PMe2Ph)2RhHB10H8(OMe)2] and [(PMe2Ph)2RhHB10H8Cl(OMe)]

Abstract

The reaction between [RhCl₃(PMe₂Ph)₃] and closo-[B₁₀H₁₀]^2– in refluxing McOH gives [1,1(PMe₂Ph)₂–1,2-µ-H-2,5-(OMe)₂-isocloso–1-RhB₁₀H₈] as a bright yellow air-stable compound in low yield. Crystals are triclinic, space group P with a= 948.8(4), b= 1 675.5(6), c= 1 855.0(6) pm, α= 101.48(3), β= 99.55(3), γ= 99.82(3)°, and Z= 4. An occasional by-product of the reaction is the yellow compound [1,1-(PMe₂Ph)₂–1,2-µ-H-2-Cl-5-OMe-isocloso–1-RhB₁₀H₈], crystals of which are orthorhombic, space group P2₁2₁2₁, with a= 1 267.5(3), b= 1 269.9(3), c= 1 683.4(3) pm, and Z= 4. In each compound the RhB₁₀ cluster is a closed eleven-vertex deltahedron, the hexahapto borane-metal linkage being effected via one Rh–H–B and five Rh–B connectivities. The metal centre is an 18-electron d⁶ rhodium(III) atom which can be thought to contribute four orbitals to the metallaborane cluster bonding scheme, thus inducing ‘isocloso’ cluster character. The presence of a bridged metal–hydrogen–boron linkage on the closed polyhedral cluster is also notable.