A number of cyclic phosphines (PR)n, where R = Ph, Me, Et, and n = 4 or 5, and arsenobenzene (AsPh)6 has been found to react with metal carbonyls to give coordination compounds such as (PPh)4Ni(CO)3, (PR)5M(CO)n (where n = 5, 4, or 3, and M = Cr, Mo, or W), (PR)4[Fe(CO)3]2, and (AsPh)6Mo(CO)4.