Phosphonium Ylides with Functionalized Silyl Substituents

Two series of aminophosphonium ylides with reactive alkoxychlorosilyl substituents (R 2 N) 3 P=CHSi(OR') 2 Cl ( 1‐8 , R = Me, Et/R' = Me, Et, i Pr, t Bu) have been prepared by reaction of the aminophosphonium ylides (R 2 N) 3 P = CH 2 with the corresponding dialkoxydichlorosilanes Cl 2 Si(OR') 2 . Substituent effects have been investigated by heteronuclear solution NMR studies of the nuclei 1 H, 13 C, 15 N, 17 O, 29 Si, and 31 P. These studies show an alternating shielding effect along the C–O–Si–C backbone. Further reactions of the chlorosilylated ylides with the aminomethylenephosphorane (Me 2 N) 3 P=CH 2 lead to the formation of the bis‐ylidic compounds [(Me 2 N) 3 P=CH] 2 Si(OR') 2 ( 9 , 10 ), which are also available in one‐pot syntheses. The molecular structure of [(Me 2 N) 3 P=CH] 2 Si(O i Pr) 2 ( 9 ) has been confirmed by single‐crystal X‐ray diffraction. In the crystal the molecules have two ylidic carbon centers with planar configuration, which are bridged by a nearly tetrahedral silicon atom. Short P–C and Si–C distances indicate a stabilizing effect of the carbanionic centers.