Tin(II) Hydrides as Intermediates in Rearrangements of Tin(II) Alkyl Derivatives

Abstract

Reactions of the Sn(II) hydrides [ArSn(μ-H)] 2 ( 1 ) (Ar = Ar iPr4 ( 1a ), Ar iPr6 ( 1b ); Ar iP4 = C 6 H 3 -2,6-(C 6 H 3 -2,6- i Pr 2 ) 2, Ar iPr6 = C 6 H 3 -2,6-(C 6 H 2 -2,4,6- i Pr 3 ) 2 ) with norbornene (NB) or norbornadiene (NBD) readily generate the bicyclic alkyl-/alkenyl-substituted stannylenes, ArSn(norbornyl) ( 2a or 2b ) and ArSn(norbornenyl) ( 3a or 3b ), respectively. Heating a toluene solution of 3a or 3b at reflux afforded the rearranged species ArSn(3-tricyclo[2.2.1.0 2,6 ]heptane) ( 4a or 4b ), in which the norbornenyl ligand is transformed into a nortricyclyl group. 1 H NMR studies of the reactions of 4a or 4b with tert -butylethylene indicated the existence of an apparently unique reversible β-hydride elimination from the bicyclic substituted aryl/alkyl stannylenes 2a or 2b and 3a or 3b . Mechanistic studies indicated that the transformation of 3a or 3b into 4a or 4b occurs via a β-hydride elimination of 1a or 1b to regenerate NBD. Kinetic studies showed that the conversion of 3a or 3b to 4a or 4b is first order. The rate constant k for the conversion of 3a into 3b was determined to be 3.33 × 10 –5 min –1, with an activation energy E a of 16.4 ± 0.7 kcal mol –1 .