Lithiation of Tris(alkyl- and arylamido)orthophosphates EP[N(H)R]₃ (E = O, S, Se): Imido Substituent Effects and PE Bond Cleavage

In the solid state, OP[N(H)Me]3 (1a) and OP[N(H)tBu]3 (1b) have hydrogen-bonded structures that exhibit three-dimensional and one-dimensional arrays, respectively. The lithiation of 1b with 1 equiv of nBuLi generates the trimeric monolithiated complex (THF){LiOP(NtBu)[N(H)tBu]2}3 (4), whereas reaction with an excess of nBuLi produces the dimeric dilithium complex {(THF)2Li2OP(NtBu)2[N(H)tBu]}2 (5). Complex 4 contains a Li2O2 ring in an open-ladder structure, whereas 5 embraces a central Li2O2 ring in a closed-ladder arrangement. Investigations of the lithiation of tris(alkyl or arylamido)thiophosphates, SP[N(H)R]3 (2a, R = iPr; 2b, R = tBu; 2c, R = p-tol) with nBuLi reveal interesting imido substituent effects. For the alkyl derivatives, only mono- or dilithiation is observed. In the case of R = tBu, lithiation is accompanied by P−S bond cleavage to give the dilithiated cyclodiphosph(V/V)azane {(THF)2Li2[(tBuN)2P(μ-NtBu)2P(NtBu)2]} (9). Trilithiation occurs for the triaryl derivatives EP[N(H)Ar]3 (E = S, Ar = p-tolyl; E = Se, Ar = Ph), as demonstrated by the preparation of {(THF)4Li3[SP(Np-tol)3]}2 (10) and {(THF)4Li3[SeP(NPh)3]}2 (11), which are accompanied by the formation of small amounts of 10·[LiOH(THF)]2 and 11·Li2Se2(THF)2, respectively.