σ-bonded complexes of substituted phospha- and arsacarboranes and their π-ollyl derivatives

The photochemical reaction of (1,7-B₉H₉CHE)₂Fe²⁻ (E  P or As) with Group VI metal carbonyls leads to the formation of complexes with the general formula, [1,7-B₉H₉CHE-M(CO)₅]₂Fe²⁻. It is proposed that each heteroatom carborane ligand is π-bonded to the iron atom and σ-bonded through either the phosphorus or arsenic atom to a Group VI metal carbonyl. The preparation and characterization of a neutral phosphacarborane σ-complex is described.