Phosphinimido Complexes of Silicon, Tin, and Germanium

The preparation of a silyl−phosphinimide of the form (R₃PN)SiMe₃ (R = Me (1), i-Pr (2), Ph (3), t-Bu (4)) was achieved by the conventional literature methodology of oxidation of phosphine by N₃SiMe₃. The analogous species (t-Bu₃PN)MMe₃ (M = Ge (5), Sn (6)) were derived via a stoichiometric reaction of the salt Li[NP-t-Bu₃] with Me₃MCl. Similarly, the species (t-Bu₃PN)₂MMe₂ (M = Si (7), Ge (8), Sn (9)), (i-Pr₃PN)SnMe₃ (10), (i-Pr₃PN)₂SnMe₂ (11), and (t-Bu₃PN)₂SnMeCl (12) were prepared. Subsequent reactions of 12 afforded (t-Bu₃PN)₃SnMe (13) and (t-Bu₃PN)₂Sn(Ot-Bu)Me (14). In analogous metathesis reactions R₃PNSnPh₃ (R = t-Bu (15), i-Pr (16)), (t-Bu₃PN)₂SnPh₂ (17), and (t-Bu₃PN)₂Sn(t-Bu)₂ (18) were also prepared. Reaction of i-Pr₃PNH and ClSnMe₃ gave (i-Pr₃PNH)SnMe₃Cl (19), whereas 6 was obtained from the reaction of t-Bu₃PNH with Me₃SnCl. The reaction of 1 with B(C₆F₅)₃ resulted in the formation of Me₃PN(SiMe₃)B(C₆F₅)₃ (20), whereas the phosphinimines 2 and 3 react with B(C₆F₅)₃ in a 2:1 ratio to give [R₃PNSiMe₂(N(PR₃)SiMe₃)][MeB(C₆F₅)₃] (R = i-Pr (21), Ph (22)). In contrast, reaction of 4 and 6 with B(C₆F₅)₃ afforded [((μ-t-Bu₃PN)MMe₂)₂][MeB(C₆F₅)₃]₂ (M = Si (23), Sn (24)). The analogous reaction of 7 and 9 with B(C₆F₅)₃ gave products formulated as [((t-Bu₃PN)₂MMe)₂][MeB(C₆F₅)₃]₂ (M = Si (25), Sn (26)) and [((i-Pr₃PN)₂SnMe)₂][MeB(C₆F₅)₃]₂ (27). Complexes 7−9, 17, 19, 20, and 24 were characterized crystallographically. The implications of this chemistry with regard to the steric demands of phosphinimide ligands are considered.