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

Heteroleptic bis(silyl)amides of magnesium and calcium [(L)M{N(SiMe3 )2 }] [M = Mg, Ca; LH = 1,4,7-trimethyl-1,4,7,10-tetraazacyclododecane; (Me3 TACD)H] were previously synthesized from LH and [M{N(SiMe3 )2 }2 ]. Strontium bis(silyl)amides [Sr{N(SiMe3 )2 }2 (thf)2 ] and [Sr{N(SiHMe2 )2 }2 (thf)2/3 ] reacted with LH to give different types of products, depending on the presence of the β-SiH function. While the former underwent protonolysis to give the amido-bridged dimer [(L)Sr{N(SiMe3 )2 }]2 (1), the latter gave the adduct [(LH)Sr{N(SiHMe2 )2 }2 ] (2) as a stable solid. 2 slowly underwent an intramolecular Si-H/H-N dehydrocoupling in solution to give [{(L)SiMe2 N(SiHMe2 )}Sr{N(SiHMe2 )2 }] (3) by liberating H2 . The results of transamination of 1 with HN(SiHMe2 )2 depended on the relative stoichiometric ratio. A 1 : 1 mixture in n-pentane gave [{(L)SiMe2 N(SiHMe2 )}Sr{N(SiMe3 )2 }] (4) and H2 , while excess HN(SiHMe2 )2 gave the adduct 2 under similar conditions. Compounds 2 and 3 exhibit Sr↼H-Si interactions according to X-ray crystallography, NMR, and IR spectroscopy. Lighter congeners of elusive [(L)Sr{N(SiHMe2 )2 }] were isolable for Mg (5) and Ca (6).