Synthesis of Cationic Calcium Amido Complexes via Silylium-Mediated Abstraction Reactions

The two molecular calcium amides [( dtbp Cbz)Ca(thf)N(SiMe 3 ) 2 ] and [( dtbp Cbz)CaN(SiMe 3 ) 2 ] (dtbp = 3,5-di- tert -butylphenyl, Cbz = carbazolyl) were reacted with the silylium salt [(Et 3 Si) 2 H][B(C 6 F 5 ) 4 ] in an attempt to facilitate abstraction of the bis(trimethylsilyl)amido ligand. However, abstraction of the silylamide was not observed in either case, and distinct cationic calcium amides were isolated. In the reactions with the tetrahydrofuran-coordinated starting material, the carbazolide-free salts [(C 6 H 6 )CaN(SiMe 3 ) 2 ] 2 [B(C 6 F 5 ) 4 ] 2 ( 1A ) and [(C 7 H 8 )Ca{N(SiMe 3 ) 2 } 2 ][B(C 6 F 5 ) 4 ] 2 ( 1B ) were isolated, indicating the cleavage of the metal–nitrogen bond to the carbazolyl moiety. With the THF-free starting material, a methyl group from a trimethylsilyl moiety was abstracted instead. Subsequently, the generated silylium ion inserted into the metal–nitrogen bond between the carbazolyl ligand and the calcium metal, yielding [ dtbp Cbz-SiMe 2 -N(SiMe 3 )-Ca][B(C 6 F 5 ) 4 ] ( 2 ) as the product.