Alkaline-Earth Metal Bis[bis(trimethylsilyl)amide] Complexes with Weakly Coordinating 2,2,5,5-Tetramethyltetrahydrofuran Ligands

The reaction of [(Me 3 Si) 2 N-Ae{μ-N(SiMe 3 ) 2 }] 2 with 2,2,5,5-tetramethyltetrahydrofuran in pentane yields the mononuclear complexes [(Me 4 thf)Ae{N(SiMe 3 ) 2 } 2 ] (Ae = Mg ( 1 ), Ca ( 2 ), Sr ( 3 ), and Ba ( 4 )) with three-coordinate alkaline-earth metal centers. With increasing radius of the alkaline-earth metal atoms, the N–Ae–N bond angles decrease. These ether adducts significantly enhance the solubility of the bis(trimethylsilyl)amides of the alkaline-earth metals in hydrocarbon solvents. Contrary to the magnesium derivative 1, the heavier congeners dissociate into mononuclear [Ae{N(SiMe 3 ) 2 } 2 ] and free Me 4 THF without formation of sparingly soluble dinuclear [(Me 3 Si) 2 N-Ae{μ-N(SiMe 3 ) 2 }] 2 .