X-ray Crystal Structures and Some Solution Structures of Lithium Amides with Intramolecular Complexation of Lithium by Tertiary Amide Groups
✍ Scribed by G. L. J. van Vliet; F. J. J. de Kanter; M. Schakel; G. W. Klumpp; A. L. Spek; M. Lutz
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 116 KB
- Volume
- 5
- Category
- Article
- ISSN
- 0947-6539
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✦ Synopsis
Lithium bis(N,N-dimethyl-2-aminoethyl)amide (1 a) and lithium N-methyl-N- (3,6-diaza-3,6-dimethyl)heptylamide (2) are dimers in toluene, THF and in the crystalline state where they exhibit diamond-shaped Li 2 N 2 cores. Tetracoordination of lithium is achieved by intramolecular binding of the amine nitrogen atoms. The dimers are broken down by hexamethylphosphoramide (HMPA), in the case of 1 a via 1 a ´HMPA, into solvent-separated ion pairs RR'N À [Li(HMPA) 4 ] (R, R' Me 2 NCH 2 CH 2 , Me 2 NCH 2 CH 2 ; Me 2 NCH 2 CH 2 (Me)NCH 2 CH 2 , Me). For lithium Nmethyl-N-(N',N'-dimethyl-2-aminoethyl)amide (3 a), seven 6 Li NMR signals are observed in toluene. In THF, 3 a ´2 THF prevails, addition of HMPA leads to solventseparated ion pairs through several intermediate species.