Reactions of CO 2 and related heteroallenes with CF 3-substituted aromatic silylamines of tin

Abstract

In this report we detail the synthesis and characterization of new Sn(II) complexes containing the –N[(SiMe 3)(Ar F)] ligand [Ar F = 3,5-(CF 3) 2C 6H 3)], specifically designed to provide both an electron-withdrawing –Ar F group as well as the –SiMe 3 group required for migration to oxygen. As well, we have also examined the reaction of the LiN[(SiMe 3)(Ar F) precursor with CO 2 and observed the formation of a bicyclic lithium carbamate consisting of two 8-membered rings characterized by single crystal X-ray crystallography. The desired starting complex Sn[N(SiMe 3)(Ar F)] 2 could be prepared directly via a metathesis reaction, although X-ray quality crystals could not be grown. The reactions of this complex with CO 2, OCS, and CS 2 are described. Reaction with CO 2 results in an unexpected insertion reaction quite dissimilar to those seen in the literature. A proposed route that explains the surprising CO 2 reaction chemistry and products is given. Reactions of Sn[N(SiMe 3)(Ar F)] 2 with OCS led to multiple products, while reaction with CS 2 led to simple insertion to form a dithiocarbamate. Interestingly, an attempt to purify Sn[N(SiMe 3)(Ar F)] 2 by distillation led to an unexpected cyclization reaction with activation of an aromatic H atom. This ortho-metallated product from this cyclization reaction was clearly identified via X-ray crystallography.