Phosphaisonitrile umpolung – synthesis and reactivity of chloro aminophosphino carbynes

Abstract

Sequential treatment of [W(CBr)(CO)₂(Tp*)] (Tp* = hydrotris(dimethylpyrazolyl)borate) with ⁿBuLi and Cl₂PNⁱPr₂ provides the aminochlorophosphinocarbyne [W(CPClNⁱPr₂)(CO)₂(Tp*)]. The chloro substituent undergoes subsitution with RLi (R = Me, Et, Ph) to afford [W(CPRNⁱPr₂)(CO)₂(Tp*)] and with [W(CLi)(CO)₂(Tp*)] to give the aminobis(alkylidynyl)phosphine [ⁱPr₂NP{CW(CO)₂(Tp*)}₂]. Treatment with Li[BHEt₃] gives the primary aminophosphine [W(CPHNⁱPr₂)(CO)₂(Tp*)], formed in a mixture with the ethyl derivative [W(CPEtNⁱPr₂)(CO)₂(Tp*)]. Although they could not be isolated, spectroscopic data indicated that halide abstraction with Al₂Cl₆ forms the phosphaisonitrile salt [W(CPNⁱPr₂)(CO)₂(Tp*)][AlCl₄], which displays electrophilic character at phosphorus, e.g., in the reaction with diphenylacetylene to furnish the phosphirenium salt [W{CP(C₂Ph₂)NⁱPr₂}(CO)₂(Tp*)][AlCl₄]. Finally, the reaction with LiNPh₂ gives the mixed diaminophosphinocarbyne, [W{CP(NⁱPr₂)(NPh₂)}(CO)₂(Tp*)].