Synthesis and structural characterization of solvated calcium amides containing bulky silylamide ligands

A series of solvated calcium bis(amides) with the general formula Ca[N(R)(SiMe3)](2)(Solv)(x) (R = -SiMe(2)t-Bu, -SiPh(2)t-Bu, and -SiPh3) was prepared from the reaction of CaI2 With 2 equiv of the corresponding potassium amide. Solvent ligands used in this study include THF, pyridine (py), hexamethylphosphoranide (HMPA), and 4-dimethylaminopyridine (DMAP). The coordinated THF in Ca[N(SiMe(2)t-Bu)(SiMe3)](2)(THF)(2) could be replaced by stronger donating ligands. When -N[(SiPh3)(SiMe3)] was used as the amide ligand again a bis(THF) adduct was formed. Quite interestingly, when the more sterically-demanding ligand N[(SiPh(2)t-Bu)(SiNle(3))] ligand was used only one THF molecule could coordinate to Ca, leading to a rare example of a tri-coordinate Ca bis(amide). One of the starting amides, [KN(SiMe(2)t-Bu)(SiMe3)](2), was isolated and found to adopt a dimeric structure in the solid state. All complexes were characterized with H-1 NMR, C-13 NMR, elemental analyses, and X-ray crystallography when appropriate. (c) 2005 Elsevier B.V. All rights reserved.