Phosphinimido Complexes of Silicon, Tin, and Germanium

Abstract

The preparation of a silyl−phosphinimide of the form (R 3 PN)SiMe 3 (R = Me ( 1 ), i- Pr ( 2 ), Ph ( 3 ), t- Bu ( 4 )) was achieved by the conventional literature methodology of oxidation of phosphine by N 3 SiMe 3 . The analogous species ( t- Bu 3 PN)MMe 3 (M = Ge ( 5 ), Sn ( 6 )) were derived via a stoichiometric reaction of the salt Li[NP -t- Bu 3 ] with Me 3 MCl. Similarly, the species ( t- Bu 3 PN) 2 MMe 2 (M = Si ( 7 ), Ge ( 8 ), Sn ( 9 )), ( i- Pr 3 PN)SnMe 3 ( 10 ), ( i- Pr 3 PN) 2 SnMe 2 ( 11 ), and ( t -Bu 3 PN) 2 SnMeCl ( 12 ) were prepared. Subsequent reactions of 12 afforded ( t -Bu 3 PN) 3 SnMe ( 13 ) and ( t -Bu 3 PN) 2 Sn(O t -Bu)Me ( 14 ). In analogous metathesis reactions R 3 PNSnPh 3 (R = t- Bu ( 15 ), i- Pr ( 16 )), ( t -Bu 3 PN) 2 SnPh 2 ( 17 ), and ( t -Bu 3 PN) 2 Sn( t -Bu) 2 ( 18 ) were also prepared. Reaction of i -Pr 3 PNH and ClSnMe 3 gave ( i- Pr 3 PNH)SnMe 3 Cl ( 19 ), whereas 6 was obtained from the reaction of t- Bu 3 PNH with Me 3 SnCl. The reaction of 1 with B(C 6 F 5 ) 3 resulted in the formation of Me 3 PN(SiMe 3 )B(C 6 F 5 ) 3 ( 20 ), whereas the phosphinimines 2 and 3 react with B(C 6 F 5 ) 3 in a 2:1 ratio to give [R 3 PNSiMe 2 (N(PR 3 )SiMe 3 )][MeB(C 6 F 5 ) 3 ] (R = i- Pr ( 21 ), Ph ( 22 )). In contrast, reaction of 4 and 6 with B(C 6 F 5 ) 3 afforded [((μ- t- Bu 3 PN)MMe 2 ) 2 ][MeB(C 6 F 5 ) 3 ] 2 (M = Si ( 23 ), Sn ( 24 )). The analogous reaction of 7 and 9 with B(C 6 F 5 ) 3 gave products formulated as [(( t -Bu 3 PN) 2 MMe) 2 ][MeB(C 6 F 5 ) 3 ] 2 (M = Si ( 25 ), Sn ( 26 )) and [(( i -Pr 3 PN) 2 SnMe) 2 ][MeB(C 6 F 5 ) 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.