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 a Silylene Complex over a Phosphenium Complex

Abstract

The reactions of (R1 = Me, Et, R2 = Me, Et) (1) with a Lewis acid (BF3·OEt2 or Me3SiOSO2CF3 (TMSOTf)) have 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 the phosphorus is abstracted, to give the cationic phosphenium complex (3). The reaction with an equimolar amount of BF3·OEt2 leads only to fluorination of the silyl group and isolation of (R = R1 or R2) (2), indicating that BF3·OEt2 reacts preferably with the OR group on Si rather than with that on P. In the reaction with equimolar or excess TMSOTf, an OR1 group on Si is abstracted selectively to give the corresponding silylene complex (5). Complex 5 was characterized by spectroscopic data and by its further reaction with a Lewis base such as pyridine or PMe3, leading to the corresponding base-stabilized silylene complex. The structure of the PMe3-stabilized silylene complex (7b) has been determined by single-crystal X-ray diffraction.