Phosphines Bearing Alkyne Substituents: Synthesis and Hydrophosphination Polymerization

A synthetic route is described for a series of phosphines bearing pendant alkyne substituents, from the conversion of BrC6H2R2C CR' (R = Me, i-Pr; R' = Ph, SiMe3) to [(mu-Br)Cu(Et2N)(2)PC6H2R2C CR'](2) and subsequently to Cl2PC6H2R2C CR' and H2PC6H2R2C CR'. Lithiation and subsequent alkylation yield the secondary phosphines R(H)PC6H2(i-Pr)(2)C CPh (R = CH(2)i-Pr, CH2Ph). Intermolecular hydrophosphination-polymerization is used to prepare the polymeric species [RPC6H2(i-Pr)(2)CH=CPh](n), which can then be sulfurized to give [RP(S)C6H2(i-Pr)(2)CH=CPh](n). The polymeric products were characterized by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and gel permeation chromatography. These data indicate a degree of polymerization (DPn) Of up to 60. Discussion of the mechanism is augmented with gas-phase density functional theory calculations.