Aminodimethylalane (Me 2 AlNH 2 ): Matrix Isolation and ab Initio Calculations
1996; American Chemical Society; Volume: 118; Issue: 27 Linguagem: Inglês
10.1021/ja953105o
ISSN1943-2984
Autores Tópico(s)Crystallography and molecular interactions
ResumoThe calculated harmonic frequencies (RMP2(fc)/6-31G*) of the three isomeric alanes Me3Al·NH3, Me3Al·15NH3, and Me3Al·ND3 are assigned to the measured IR absorptions of these compounds, matrix isolated in argon at 10 K. The results are compared with the known literature data. The irradiations of the matrix-isolated amine adducts yield aminodimethylalane. The experimental IR data of the three isotopomers Me2AlNH2, Me2Al15NH2, and Me2AlND2 agree well with the calculated harmonic frequencies. Elucidated from ab initio calculations, Me2AlNH2 is a C2v-symmetrical molecule with an AlN bond length of 1.790 Å. This AlN distance is 15% shorter than that of the starting compound Me3Al·NH3 (2.106 Å). The predicted AlN rotation barrier of 40.7 kJ mol-1 is much lower than the known barriers of the isoelectronic silaalkenes and the lighter congeners, aminoboranes and alkenes, respectively.
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