Selective abstraction of an OR group in the reaction of (C5H5)(CO)Fe{SiMe2(OR1)}{PN(Me)CH2CH2NMe(OR2)} with a Lewis acid: Preferential formation of asilylene complex over a phosphenium complex

The reactions of Cp(CO)Fe{SiMe2(OR1)} {PN(Me)CH2CH2NMe(OR2)} (R-1 = Me, Et, R-2 = Me, Et) (1) with a Lewis acid (BF3. OEt2 or Me3SiOSO2CF3 (TMSOTf)) h ave been examined. In the reaction with an excess of BF3. OEt2, not only is an OR group on Si replaced by fluoride but also an OR group attached to th e phosphorus is abstracted, to give the cationic I phosphenium complex Cp(C O)Fe(SiMe2F){PN(Me)CH2CH2NMe}+BF4- (3). The reaction with an equimolar amou nt of BF3. OEt2 leads only to fluorination of the silyl group and isolation of Cp(CO)Fe{SiMe2F}{PN(Me)CH2CH2NMe(OR)} (R = R-1 or R-2) (2), indicating that BF3. OEt2 reacts preferably with the OR group on Si rather than with t hat on P. In the reaction with equimolar or excess TMSOTf, an OR1 group on Si is abstracted selectively to give the corresponding silylene complex Cp( CO){PN(Me)CH2CH2NMe(OR2)}Fe=SiMe2. OTf (5). Complex 5 was characterized by spectroscopic data and by its further reaction with a Lewis base such as py ridine or PMe3, leading to the corresponding base-stabilized silylene compl ex. The structure of the PMe3-stabilized silylene complex [Cp(CO){PN(Me)CH2 CH2NMe(OEt)}Fe=SiMe2. PMe3]OTf (7b) has been determined by single-crystal X -ray diffraction.