Rearrangement of bis(alkylidynyl)phosphines to phospha-acyls

A range of bis(alkylidynyl)phosphines RP{C[triple bond, length as m-dash]M(CO) 2 (Tp*)} 2 (M = Mo, W; R = Cl, Ph, Cy; Tp* = hydrotris(dimethylpyrazolyl)borate) are obtained from the reactions of [M([triple bond, length as m-dash]CLi)(CO) 2 (Tp*)] with Cl 2 PR or alternatively via the palladium(0)-mediated reactions of [W([triple bond, length as m-dash]CBr)(CO) 2 (Tp*)] with RPH 2 (R = Py, Cy). The complexes RP{C[triple bond, length as m-dash]W(CO) 2 (Tp*)} 2 rearrange slowly (R = Cl) or on heating (R = Ph) to afford the isomeric phospha-acyls [W 2 (μ:η 1 -C;η 2 -C,P-CCPR)(CO) 4 (Tp*) 2 ].