SILYL AND PHOSPHINO SUBSTITUTED METHANES - SYNTHETIC AND STRUCTURAL INVESTIGATIONS OF THE REACTIVITY OF AMBIDENTATE PHOSPHINOMETHANIDES

LiCH(PMe(2))(2) reacts with SiCl4 or with PhR(2)SiCl (R = Me, Ph) via the carbanion to give silyl substituted phosphino methanes; Cl2Si[CH(P Me(2))(2)](2) (3) or PhR(2)Si[CH(PMe(2))(2)] (4) (R = Me) and (5) (R = Ph), respectively. 4 and 5 are deprotonated by (n)BuLi to give trimer ic {Li[C(PMe(2))(2)(SiMe(2)Ph)]}(3) (6) and in the precence of TMEDA, monomeric {Li[C(PMe(2))(2)(SiMe(2)Ph)]}. TMEDA (7) or {Li[C(PMe(2))(2) (SiPh(3))]}. TMEDA (8), respectively. {Li[C(PMe(2))(SiMe(3))(2)]}(2). TMEDA reacts with R(2)SiCl(2) (R = Me, Cl) via both the carbanion, thu s generating a tetraheteroatom substituted methane moiety and, in a se cond substitution step, via phosphorus, thus generating an ylidic moie ty. The obtained compounds (Me(3)Si)(2)(PMe(2))C-SiR(2)-PMe(2)=C(SiMe( 3))(2) (9) (R = Me) and (10) (R = Cl) are structurally characterized b y X-ray crystallography as well as compounds 3, 5, 6 and 7. The observ ed variations in bond lengths and angles are explained to be mainly du e to steric congestion. The ambidentate nature of phosphinomethanides thus clearly can be influenced by the nature of their carbanion substi tuents.