Hexa-coordinated strontium silylamide complex stabilized by tetradentate alkoxy ligand

Abstract

The heavier group 2 metal bis(trimethylsilyl)amides [M(btsa)2; M= Mg, Ca, Sr, and Ba] are efficient catalysts for hydroamination reactions, but their extreme sensitivity to air and moisture makes them experimentally inconvenient. Therefore, the substitution of one btsa ligand of M(btsa)2 for a sterically bulky amidinate or a β-diketiminate ligand was accepted as a worthy strategy for increasing the stability of the complexwhile retaining its reactivity.1-6 The bulky amidinate and diketiminate ligands that are used to substitute one btsa group of M(btsa)2 effectively stabilize smallermetal cations (Mg and Ca), whereas the biggermetal centers (Sr and Ba) have a propensity to assume a six-coordinated (rather than a three- or four-coordinated) state. This makes partially substituted heavier alkaline-earth metal amides far from stable for easy use, which reiterates the necessity of having a reasonably stable, partially substituted strontium bis(trimethylsilyl)amide for smooth handling while retaining its reactivity. Here we describe the synthesis of a dimeric strontium complex with six-coordinated metal centers, which contains two bis(trimethylsilyl)amides groups and two tetradentate alkoxide ligands. © 2015 Korean Chemical Society