Crystal structure and fluxional behaviour in solution of [Rh4(CO)6(μ-Me2PCH2PMe2)3]

Abstract

[Rh₄(CO)₆(μ-Me₂PCH₂PMe₂)₃], the first example of a hexasubstituted derivative of Rh₄(CO)₁₂, has a ground state geometry in the solid state and in solution of C_s symmetry with four edge-bridging carbonyls and with each diphosphine ligand bridging one edge of the same Rh₃ face. The result is an imbalance of the formal electron count at two rhodium atoms. As observed by ¹³C- and ³¹P-NMR, the mobility of the ligands is restricted to one μ-CO ↔ η-CO site exchange which astonishingly does not average dynamically the electron count on all four metal atoms.