PUB - Publikationen an der Universität Bielefeld

The dimethylaminomethyl compounds (Me2AlCH2NMe2)(2) (1), (Me2GaCH2NMe2)2 (2), (Me-2-InCH2NMe2)(2) (3), (Me2AlCH2NMe2).(MeClAlCH2NMe2) (4), [ClAl(CH2NMe2)(2)](2) (5), and [Al-(CH2NMe2)(3)](2) (6) have been prepared by reacting LiCH2NMe2 with the corresponding element or organoelement chlorides. Characterization was undertaken by means of elemental analyses, NMR spectroscopy (H-1, C-13, Al-27), and mass spectrometry. An unusually low Al-27 NMR chemical shift of 6 (62 ppm) was observed indicating a possible coordination number higher than four at aluminum in solution. The crystal structures of all compounds but 3 have been determined and confirm that all form dimers with six-membered M2C2N2 rings in the chair conformation. The mass spectra indicate that the dimers are retained in the gas phase, and for 1 the molecular dynamics of ring inversion was monitored in solution by variable-temperature NMR spectroscopy, showing that the barrier for the inversion process (9 kcal mol(-1)) is comparable to that of cyclohexane. Calculations at the B3LYP/6-311G(d) level of theory confirm that the molecular structures of 1 and 2 are almost undistorted in the solid state. DFT calculations (B3LYP/6-311G(d)) for the monomeric three-membered ring isomers of 1 and 2 show these to be much higher in energy (81 and 77 kJ mol(-1) per monomer) than the corresponding six-membered ring dimers.