Complexes of organoaluminium compounds. Part 12. Preparation, nuclear magnetic resonance spectra, and the crystal and molecular structure of bis(µ-isopropylamido-dimethylaluminium)

Abstract

The title compound, [{AlMe₂(NHPrⁱ)}₂], has been made from trimethylaluminium and isopropylamine. Crystals are triclinic with a= 858.6(3), b= 1 136.6(5), and c= 1 344.0(5) pm, α= 107.48(3), β= 90.52(2), γ= 99.21(3)° and Z= 3. The structure determination (diffractometer data, 2 388 reflections, R= 0.078) shows that molecules have four-membered (AIN)₂ rings and that cis and trans isomers, mole ratio 2 : 1, crystallise together. Mean molecular parameters are: Al–N 195.2(9), Al–C 196.1(6), and N–C 149.7(8) pm. Nuclear magnetic resonance measurements show that the ratio of cis to trans isomers in solution is also close to 2 : 1 over a wide temperature range. The compound [{AlEt₂(NHPrⁱ)}₃] has also been characterised.