Stable bidentate silylene adducts of alkaline-earth amides

Abstract

The coordination chemistry of silylenes is known for a vast number of elements of all blocks of the periodic table. However, only a handful of examples of silylene complexes have been reported for heavy alkaline-earth elements, which is mainly attributed to the “hard-soft” mismatch between the “hard” metal center and the “soft” silicon donor. Herein, we report the synthesis and characterization of a series of alkaline-earth silylene complexes comprising a bidentate pyridyl-amido-silylene ligand. The isolated Ca, Sr and Ba complexes show considerably increased stability in comparison to other known alkaline-earth silylene complexes. The molecular structures of all three complexes are essentially similar. Interestingly, depending on the central metal, the 1H NMR chemical shifts of the ortho-H atom show unexpected large differences. DFT computations were conducted to elucidate this trend in the NMR resonances.