Reactions of CO2 and related heteroallenes with CF3-substituted aromatic silylamines of tin

In this report we detail the synthesis and characterization of new Sn(II) complexes containing the –N[(SiMe3)(ArF)] ligand [ArF = 3,5-(CF3)2C6H3)], specifically designed to provide both an electron-withdrawing –ArF group as well as the –SiMe3 group required for migration to oxygen. As well, we have also examined the reaction of the LiN[(SiMe3)(ArF) precursor with CO2 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(SiMe3)(ArF)]2 could be prepared directly via a metathesis reaction, although X-ray quality crystals could not be grown. The reactions of this complex with CO2, OCS, and CS2 are described. Reaction with CO2 results in an unexpected insertion reaction quite dissimilar to those seen in the literature. A proposed route that explains the surprising CO2 reaction chemistry and products is given. Reactions of Sn[N(SiMe3)(ArF)]2 with OCS led to multiple products, while reaction with CS2 led to simple insertion to form a dithiocarbamate. Interestingly, an attempt to purify Sn[N(SiMe3)(ArF)]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.

Graphical abstractLi and Sn complexes containing the new electron-withdrawing –N[(SiMe3)(ArF)] ligand [ArF = 3,5-(CF3)2C6H3)] have been prepared and their reactivities towards CO2, OCS, and CS2 examined. Sn[N(SiMe3)(ArF)]2 reacts with CO2 to produce a new O-silylated oleate ligand rather than a carbamate. A proposed route to the unexpected product is given. Reaction with CS2 led to insertion to form a dithiocarbamate. Attempts to isolate Sn[N(SiMe3)(ArF)]2 by distillation led to a unexpected ortho-metallation reaction.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Syntheses of Sn(II) complexes with electron-withdrawing ligands. ► Examined reactions of CO2, OCS, and CS2 with Sn complexes. ► Products contain bridging or chelating ligands as shown by X-ray crystallography. ► ortho-Metallation of aromatic rings with Sn(II).