Ambident σ- and π-donor ability of a neutral 10π-aromatic phosphoniobenzophospholide

1-Triphenylphosphoniobenzo[c]phospholide 2 which is accessible via NaBH4 reduction of 1,3-bis(triphenylphosphonio)benzophospholide 1 displays an ambident coordination ability similar to a phosphinine; this is shown by its reactions with (cyclooctene)Cr(CO)5 and (naphthalene)Cr(CO)3 which gave (σ(P)-2)Cr(CO)5 and (η5-2)Cr(CO)3, the first π-complex of a 10π-aromatic phosphorus heterocycle with a d-block metal.