A nearly planar stannene with a reactive tin-carbon double bond

Abstract

Bis(2,4,6-triisopropylphenyl)-2,7-di-tert-butylfluorenylidene stannane, Tip2Sn=CR2, an isolable stannene that displays a deep-purple colour, was synthesized by dehydrofluorination of the corresponding fluorostannane by tert-butyllithium. It exhibits the shortest Sn=C distance [2.003(5) Å] and the slightest twisting around this unsaturation (10°) among the known stannenes. Its reaction with benzaldehyde according to a [2+2] cycloaddition and that with α-ethylenic aldehydes and ketones such as crotonaldehyde and methyl vinyl ketone by a [2+4] cycloaddition proceeded in near-quantitative yield. With acetone, an ene reaction occurred. The fourmembered ring 1,2-oxastannacyclobutane obtained with benzaldehyde underwent a ring expansion with a second molecule of benzaldehyde to afford the six-membered ring dioxastannacyclohexane. © Wiley-VCH Verlag GmbH & Co. KGaA, 2008.