화학공학소재연구정보센터
Inorganic Chemistry, Vol.46, No.4, 1481-1487, 2007
Tripodal amido boron and aluminum complexes
The synthesis and structural elucidations of novel boron and aluminum complexes incorporating the tripodal triamido [N-3](3-) ligand framework that is hypothesized to promote the preorganized pyramidal geometry for high Lewis acidity are reported. Salt metathesis between the in situ-generated trianionic lithium complexes of the tripodal amido ligands with BCl3 leads to boranes HC[SiMe2N(4-MeC6H4)](3)B (1) and MeSi[SiMe2N(4-MeC6H4)](3)B (2); however, substitution of the N-Ar group with the bulky Bu-t affords the unexpected non-boron-containing LiCl adduct {[HC((SiMe2NBu)-Bu-t)(2)((SiMeNBu)-Bu-t)]Li-3(Et2O)Cl}(2) (3) via apparent elimination of MeBCl2. The products derived from the salt metathesis reaction with AlCl3 are determined by the reaction medium: while the reaction in a hexanes-ether mixture or toluene affords solvated salt adduct HC[SiMe2N(4-MeC6H4)](3)Al center dot ClLi(Et2O)(2) (4) or salt adduct HC[SiMe2N(4-MeC6H4)](3)Al center dot ClLi (5), respectively; the addition of a small amount of THF produces a mixture of complexes HC[SiMe2N(4-MeC6H4)](3)Al center dot(THF) (6, major) and HC[SiMe2N(4-MeC6H4)](3)Al(OCHCH2)center dot Li(THF)(2) (7, minor). The desired complex 6 can be exclusively formed using HC[SiMe2N(4-MeC6H4)](3)Li-3 center dot(THF)(3) and the hexanes-ether mixture solvent. The molecular structures of complexes 1, 3, 5, 6, and 7 have been elucidated by X-ray diffraction studies. The structure of 1 shows an approximately trigonal pyramidal geometry at B with no significant N-B p-p pi-interactions. The strong salt adduct and solvate formation of the tripodal amido Al complex, as well as its similarity to the strong Lewis acid Al(C6F5)(3) in the THF adduct and enolaluminate formation and structure, indicate the desired core structure [N-3]Al is indeed highly Lewis acidic.