Phosphaisonitrile umpolung - synthesis and reactivity of chloro aminophosphino carbynes

Sequential treatment of [W([triple bond, length as m-dash]CBr)(CO)2(Tp*)] (Tp* = hydrotris(dimethylpyrazolyl)borate) with nBuLi and Cl2PNiPr2 provides the aminochlorophosphinocarbyne [W([triple bond, length as m-dash]CPClNiPr2)(CO)2(Tp*)]. The chloro substituent undergoes subsitution with RLi (R = Me, Et, Ph) to afford [W([triple bond, length as m-dash]CPRNiPr2)(CO)2(Tp*)] and with [W([triple bond, length as m-dash]CLi)(CO)2(Tp*)] to give the aminobis(alkylidynyl)phosphine [iPr2NP{C[triple bond, length as m-dash]W(CO)2(Tp*)}2]. Treatment with Li[BHEt3] gives the primary aminophosphine [W([triple bond, length as m-dash]CPHNiPr2)(CO)2(Tp*)], formed in a mixture with the ethyl derivative [W([triple bond, length as m-dash]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{[triple bond, length as m-dash]CP(NiPr2)(NPh2)}(CO)2(Tp*)].