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.