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 [(μ-Br)Cu(Et2N)2PC6H2R2CCR′]2 and subsequently to Cl2PC6H2R2CCR′ and H2PC6H2R2CCR′. Lithiation and subsequent alkylation yield the secondary phosphines R(H)PC6H2(i-Pr)2CCPh (R = CH2i-Pr, CH2Ph). Intermolecular hydrophosphination−polymerization is used to prepare the polymeric species [RPC6H2(i-Pr)2CHCPh]n, which can then be sulfurized to give [RP(S)C6H2(i-Pr)2CH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.