A Nearly Planar Stannene with a Reactive Tin–Carbon Double Bond

Abstract

Bis(2,4,6‐triisopropylphenyl)‐2,7‐di‐tert‐butylfluorenylidenestannane, 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 four‐membered 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, 69451 Weinheim, Germany, 2008)

In silico quest for stable phosphastannaallenes

“…The calculated values for the Sn-C distances are close to those obtained experimentally in stannenes >Sn C<: around 2 Å for the Sn C double bond [21] and between 2.10 and 2.20 Å for the Sn-C single bond [22]. The B3LYP/LANL2DZ method seems to slightly underestimate the length of the Sn C double bond for the models with R Me, but in the case of other substituents (R = H, Ph) the same trend is not observed.…”

Hydrogen abstraction from organotin di- and trihydrides by N-heterocyclic carbenes: a new method for the preparation of NHC adducts to tin(ii) species and observation of an isomer of a hexastannabenzene derivative [R6Sn6]

“…35 The number of carbene adducts to stannylenes and stannenes increased only recently. [38][39][40][41][42] The 119 Sn chemical shi for Weidenbruch's adduct was reported at d ¼ 710 ppm, whilst the herein reported compound 3 is found to resonate at d ¼ À150 ppm, meaning a higheld shi of 860 ppm caused by the change from an N-bond isopropyl residue to an ethyl moiety. 119 Sn NMR resonances in the range of À100 ppm are usually observed for tri-or tetracoordinate Sn(IV) derivatives whilst resonances shied to lower elds are indicative for a decrease of the coordination number around the Sn centre.…”

The first observation of 1J(SnC) coupling constants in tin–carbon double‐bond compounds

“…The two planes around the tin and carbon atoms were not coplanar (the dihedral angle is 28.5°), probably due to the steric repulsion of the substituents. Following this report, Escudié et al succeeded in the synthesis of 4 by enlarging the steric hindrance on the fluorenylidene unit by the substitution of the 2,7‐positions with two tert ‐butyl groups 7. The tin–carbon bond length of 4 is 2.003(5) Å, the shortest ever reported, and the twisting angle around the double bond is 10°.…”