Hydrophosphination reactions with transition metal ferrocenylphosphine complexes

Abstract

The group 6 metal mono-, bis- and tris-ferrocenylphosphine complexes [M(CO)₅(PH₂Fc)] (1a, M = Cr; 1b, M = Mo; 1c, M = W), cis-[M(CO)₄(PH₂Fc)₂] (2a, M = Cr; 2b, M = Mo; 2c, M = W) and fac-[M(CO)₃(PH₂Fc)₃] (3a, M = Cr; 3b, M = Mo; 3c, M = W) [Fc = Fe(η⁵-C₅H₄)(η⁵-C₅H₅)] were prepared and fully characterised. IR and NMR spectroscopy and single-crystal X-ray diffraction analysis indicate that FcPH₂ is as good a σ donor as PhPH₂ but is easier to handle and furthermore has a redox-active ferrocenyl group. Complex 1c was employed in the hydrophosphination of acrylonitrile and methyl acrylate in the presence of catalytic amounts of KOtBu giving the secondary phosphine complexes [W(CO)₅{PH(Fc)(CH₂CH₂CN)}] (4a) and [W(CO)₅{PH(Fc)(CH₂CH₂C(O)OMe)}] (4b). In addition, FcP(CH₂CH₂CN)₂ (5) was prepared by a similar method from FcPH₂ and acrylonitrile. These hydrophosphination products represent a convenient method for the modification of phosphines.