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

摘要

This study details the syntheses of N-heterocyclic germylenes and stannylenes featuring diazaborolyl groups, {(HCDippN)(2)B} (Dipp = 2,6-(Pr2C6H3)-Pr-i), 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(pi)-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 Sn-119 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.