A phosphoranide (10‐P‐4) anion coordinating to transition metals, as a Lewis base and a π‐acceptor

Abstract

Abstract The reaction of 10‐P‐5 hydridophosphorane 6 with KH provides the 10‐P‐4 potassium phosphoranide anion 7a . Anion 7a reacts with CpFe(CO) 2 I and BrAu(PEt 3 ) to replace the halide with the phosphoranide as a monodentate ligand forming 8 and 9 . The X‐ray structure of 8 shows that the equatorial—Fe(CO) 2 Cp ligand of 8 makes the apical PO bonds (1.824 Å) longer than the PO bonds (1.80 Å) of the phosphoranide oxide anion 10 . The PO bonds (1.75 Å) of 6 , with an equatorial proton ligand, are still shorter. This provides evidence that the—Fe(CO) 2 Cp ligand is not only a sigma‐acceptor Lewis acid ligand, but also a pi‐donor that transfers electrons into the OPO three‐center bond's anti‐bonding orbital to increase its P—O bond lengths. It is a better pi‐donor than the O − pi‐donor of phosphoranide oxide 10 .