Synthetic, structural and reaction chemistry of N-heterocyclic germylene and stannylene compounds featuring N-boryl substituents

Abstract

This study details the syntheses of N-heterocyclic germylenes and stannylenes featuring diazaborolyl groups, {(HCDippN)₂B} (Dipp = 2,6-ⁱPr₂C₆H₃), as both of the N-bound substituents, with a view to generating electron rich and sterically protected metal centres. The energies of their key frontier orbitals – the group 14-centred lone pair and orthogonal p_π-orbital (typically the HOMO−2 and LUMO) have been probed by DFT calculations and compared with a related acyclic analogue, revealing (in the case of the stannylenes) a correlation with the measured ¹¹⁹Sn chemical shifts. The reactivity of the germylene systems towards oxygen atom transfer agents has been examined, with 2 : 1 reaction stoichiometries being observed for both Me₃NO and pyridine N-oxide, leading to the formation of products thought to be derived from the activation of C–H bonds by a transient first-formed germanone.