Group 2 metal (Mg, Ca, Sr) silylamides supported by a cyclen-derived macrocyclic polyamine

Area of Science:

• Organometallic chemistry
• Coordination chemistry
• Main group chemistry

Background:

• Heteroleptic bis(silyl)amides of magnesium and calcium were previously synthesized.
• Strontium bis(silyl)amides exhibit diverse reactivity with the 1,4,7-trimethyl-1,4,7,10-tetraazacyclododecane ligand (LH).

Purpose of the Study:

• To investigate the reaction of strontium bis(silyl)amides with LH, focusing on the role of the beta-SiH function.
• To characterize the resulting products, including adducts and dehydrocoupled species.
• To explore the potential for Si-H/H-N dehydrocoupling and transamination reactions.

Main Methods:

• Synthesis of heteroleptic bis(silyl)amides of Mg, Ca, and Sr.
• Reaction of strontium bis(silyl)amides with LH under varying conditions.
• X-ray crystallography, NMR, and IR spectroscopy for structural characterization.
• Transamination reactions to study ligand exchange.

Main Results:

• Protonolysis of [Sr{N(SiMe3)2}2(thf)2] with LH yielded an amido-bridged dimer.
• Reaction with [Sr{N(SiHMe2)2}2(thf)2/3] led to adduct formation and subsequent intramolecular Si-H/H-N dehydrocoupling, liberating H2.
• Transamination reactions showed dependence on stoichiometric ratios, yielding different products.
• Compounds 2 and 3 exhibited Sr-H-Si interactions confirmed by spectroscopic and crystallographic data.
• Lighter congeners for Mg and Ca were isolated.

Conclusions:

• The presence of the beta-SiH function in strontium bis(silyl)amides is crucial for directing reaction pathways with LH.
• Intramolecular dehydrocoupling and hydrogen release are feasible reactions for these strontium complexes.
• Sr-H-Si interactions play a significant role in the structural stabilization of these compounds.
• This study provides insights into the coordination chemistry of strontium and related lighter congeners.