SYNTHESIS AND PROBLEMATIC CRYSTAL-STRUCTURES OF [AL(CH3CN)(6)][MCL(6)](3)(CH3CN)(3) (M=TA, NB OR SB)

Compounds of formula [Al(CH3CN)(6)][MCl(6)](3)(CH3CN)(3) (M = Ta (1); Nb (2); Sb (3)) have been synthesized from the reactions of MCl(5) and AlCl3 in acetonitrile and characterized by X-ray crystallography. Com plex 1 crystallizes in the tetragonal space group P4/mbm with a = b = 10.408(2), c = 7.670(3) Angstrom, V = 830.9(4) Angstrom(3) and Z = 2/3 . Complex 2 crystallizes in the tetragonal space group P4/mnc with a = b = 10.330( 1), c = 15.320(3) Angstrom, V = 1634.8(4) Angstrom(3) and Z = 4/3. Complex 3 also crystallizes in the tetragonal space group P4 /mnc with a = b = 10.313(1), c = 15.238(2) Angstrom, V = 1621.0(1) Ang strom(3) and Z = 4/3. The non-integer Z values for complexes 1-3 resul t from unusual problems of disorder and/or twinning in these crystal s tructures due to their high symmetry. The M-Cl distances range from 2. 329(3) Angstrom in the Ta complex to 2.355(1) Angstrom in the Sb compl ex, while the Al-N distances are similar in an three complexes, rangin g from 1.92(1) to 1.97(1) Angstrom, respectively. Complexes 1-3 are th e first structurally characterized complexes that contain a (hexaaceto nitrile) aluminum(III) cation.