Probing the Mechanism of Aldehyde Addition to a Disilene and Two Silenes: Solvent Effects

Abstract

The effect of changing the solvent from a hydrocarbon to acetonitrile on the mechanism of the addition of aldehydes to a disilene and two silenes was investigated. The products of the reaction between Mes 2 SidCH(CH 2 -t-Bu) and acetonitrile were characterized.

Addition of Nitriles to Two Brook Silenes

“…In the 1 H– 29 Si gHMBC spectrum of 14 , the signals at 1.72 and 1.23 ppm in the 1 H dimension (assigned to the CH 2 group) showed correlations to the signal at −40.9 ppm in the 29 Si dimension, assigned to the central silicon ((Me 3 Si) 2 Si ). Finally, the IR spectrum of 14 showed an absorption at 2227 cm –1 , which is consistent with the stretching vibration of a nitrile functional group and is similar in value to the nitrile stretching vibrations of 1 (2232 cm –1 ) and 4a (2243 cm –1 ) . Together, the data support the assigned structure of 14 .…”

“…The 13 C NMR spectrum of 14 revealed signals at −1.76 and 120.40 ppm, which are indicative of a saturated carbon and a nitrilic carbon, respectively. The 13 C chemical shift of the nitrilic carbon of 14 (120.40 ppm) is similar to the 13 C chemical shift of the nitrilic carbon of compound 1 (118.73 ppm) . In the 1 H– 13 C gHMBC spectrum of 14 , the 1 H signals at 1.72 and 1.23 ppm showed one-bond correlations to the 13 C signal at −1.76 ppm (assigned to the CH 2 carbon) and long-range correlations to the signal at 120.40 ppm (assigned to the nitrilic carbon).…”

“…Recently, we reported the facile preparation of 1 and 2 by the addition of excess CH 3 CN to a benzene solution of Mes 2 SiCH(CH 2 t -Bu) ( 3 ), a naturally polarized silene (Chart ) . The structure of adduct 1 , derived from CH insertion across the SiC, was not surprising based on results which date back to one of the first studies of the reactivity of silenes where Sommer reported the preparation of compounds 4a – d by the addition of acetonitrile, propionitrile, dimethylacetonitrile, and phenylacetonitrile to Me 2 SiCH 2 ( 5 ), respectively, or by the addition of acetonitrile to H 2 SiCH 2 to give compound 4e (Chart ) .…”

“…In contrast, we proposed that the formation of 1 begins with initial coordination of acetonitrile to the silenic silicon of 3 followed by abstraction of the α-CH of a second molecule of nitrile by the silenic carbon and then displacement of the coordinated nitrile by the conjugate base. Adduct 2 appears to be formed by the coordination of the nitrogen lone pair of 1 to another equivalent of silene 3 followed by an ene reaction . Wiberg also proposed a secondary reaction of a silene–nitrile coordination complex: 6 was prepared by the addition of PhCN to Me 2 SiC(SiMe 3 ) 2 ( 7 ), which was generated by the thermal elimination of LiX from Me 2 SiX–C(SiMe 3 ) 2 Li, where X = (PhO) 2 PO 2 (Chart ).…”

Reactivities of Adamantyl-Substituted Metallenes with a C═E (E = C, Si, Ge, Sn, and Pb) Double Bond. A Theoretical Study

“…On the basis of this conclusion, this reasoning can also be applied to the systems studied in this work. That is to say, the considerable polarity of the CE double bond in the adamantyl-substituted Rea-CE (E = C, Si, Ge, Sn, and Pb) reactant can relieve the symmetry restriction, and its bimolecular, pericyclic [2 + 2] reaction with a ketone is no longer forbidden (see below) …”