Complexes of organoaluminium compounds. Part IX. Crystal and molecular structure of hepta-µ3-methylimido-heptakis(methylaluminium) a cage compound in the series of oligomers [R1XYR2]n

Abstract

The compound (MeAlNMe)₇ crystallises in space group P2₁/c with a= 14.059(7)b= 14.407(8), c= 14.435(8)Å, β= 93.10(5)°, and Z= 4; the structure was solved by the symbolic addition method and least-squares refinement converged at R= 0.119 (1 179 reflections measured by diffractometer). The molecules have a cage structure with C_3v symmetry, in which each aluminium and each nitrogen atom is four-co-ordinate and bound to one methyl group and three atoms within the cage. Mean molecular dimensions are : Al–N 1.91(4),Al–C 1.98(7) N–C 1.56(6)Å: Al–N–Al 89(1) or 120(1)°. N–Al–N 90(2) or 110(2)°. C–Al–N angles range from 112 to 129°, and C–N–Al from 103 to 127°. The structure found is one of a related series shown by oligomeric molecules (R¹XYR²)_n^r(n= 1–8) a general discussion of these structures is given.