Novel Synthesis, X-ray Crystal Structures, and Spectroscopic Properties of Metalated Hypervalent Phosphorus Compounds, Cp(CO)LFe{P(OC₆H₄Y)(OC₆H₄Z)} (L = CO, P(OPh)₃, P(OMe)₃, PMe₃; Y, Z = NH, NMe, O)

Abstract

Iron phosphorane complexes, ( 1a, Y = NH; 1b, Y = NMe; 3, Y = O), have been prepared from [Cp(CO) 2 Fe{P(OPh) 3 }]PF 6, o -HOC 6 H 4 YH, and a Lewis base. ( 2a, R = H; 2b, R = Me) having two different chelates on the phosphorus has been prepared from o -HOC 6 H 4 NRH, and a Lewis base. These reactions involve nucleophilic attacks of an organic nucleophile at a trivalent phosphorus coordinated to an iron and substitution on the phosphorus. During the course of preparation of 1b, ( 4 ) was isolated, which corresponds to one of the intermediates on the reaction pathways to give 1 − 3 . 4 reacts with a Lewis base to give 1b . The reaction of hydridophosphorane with n -BuLi leads to NH proton abstraction to give the amide which then reacts with Cp(CO)LFeCl to yield ( 5, L = P(OPh) 3; 6, L = P(OMe) 3; 7, L = PMe 3 ) by an apparent 1,2-proton migration. The X-ray structures of 1b, 2b, and 4 were determined. 1b and 2b have slightly distorted trigonal-bipyramidal geometries around the phosphorus with the iron fragment in the equatorial position and have P−O eq bonds longer than those of organophosphoranes, indicating that the Cp(CO) 2 Fe fragment serves as a strong π donor. The Fe−P(phosphorane) bond rotates freely in solution even at −50 °C. A Berry pseudorotation around the phosphorane phosphorus does not occur for 1a, b, 2a, b, and 5 − 7, whereas it does for 3 .