N-allylaldiminium cation as pi-ligand: Synthesis and crystal structure of [(CH3)(2)N-C6H4-CH=NH-CH2-CH=CH2]CuX2 (X = Cl, Br) compounds

The [(CH3)(2)N-C6H4-CH=NH-CH2-CH=CH2]CuX2 [X = Cl (I) or Br (II)] complexes were prepared by ac electrochemical synthesis from N-allyl-4-(N',N'-dimeth ylamino)benzaldime (ADBA) and ethanol solution of CuCl2. 2H(2)O or CuBr2, r espectively, and their crystal structures were determined [DARCh diffractom eter, MoKalpha radiation, 989 (F greater than or equal to 4 sigma(F)) and 9 65 (F greater than or equal to 3 sigma(F)) reflections, R = 0.035 and 0.053 for I and II, respectively]. The compounds are isostructural, space group P2(1)/a, Z = 4. Unit cell parameters are a = 27.74(1), b = 7.253(3), c = 6. 852(6) Angstrom, beta = 91.05(5)degrees for I and a = 28.175(8), b = 7.392( 2), c = 7.000(2) Angstrom, beta = 90.18(3)degrees for II. The copper coordi nation polyhedron is a trigonal pyramid formed by three halogen atoms and a C=C bond. The structure is built from the centrosymmetric Cu2X4(ADBAH)(2) dimers joined together by the hydrogen bonds C-H...X [H ... Cl 2.85-2.87(8) Angstrom]. The geometry of the ADBAH(+) cation is indicative of its partia l transformation from the aromatic to quinoid form, owing to the stabilizat ion of the aldiminium cation under the +M-effect of the (CH3)(2)N group. Ne t atomic charges are calculated for I.