dc.description.abstract | The crystal structures of five complexes CulLz, L = 2-methylpyridine (1 ), 2-ethylpyridine (Z), quinoline (as its solvate) (3), 3,5-dimethylpyridine (4), and 2,6-dimethylpyridine (5), have been dgermined by single-crystal X-ray diffraction methods at 295 K. Crystals of (1) are triclinic, space group PI, with a = 10.662(5), b = 9.552(6), c = 7.936(6) A, a = 112.35(4), p = 96.20(4), y = 104.66(4)", and Z = 2 ; R = 0.037 for 1 060 ' observed ' reflections. Crystals of (2) are tetragonal, space group 14, / a d , with a = 14.826(5), c = 27.980(8) A, and Z = 16 ; R = 0.035 for 1 000 ' observed ' reflections. Crystals of (3) are triclinic, space group P7, with a = 15.85(1), b = 10.24(1), c = 7.696(7) A, a = 105.72(7), p = 92.64(7), y = 99.51 (7)", and Z = 2; R = 0.033 for 2 694 ' observed ' reflections. Crystals of (4) are monoclinic, space group C2/m, with 8 = 13.435(5), b = 16.1 27(5), c = 9.31 3(4) A, p = 127.69(3)", and Z = 2; R = 0.036 for 1 330 ' observed ' reflections. In each case, the complex is dimeric and of the form L2CuI2CuL2; the asymmetric unit is the monomer in (1) and (3) and the half monomer in (2) and (4). The dimer in (1) and (3) includes a crystallographic inversion centre, while compounds (2) and (4) have 222 and 2/m symmetry respectively. In all four complexes, each copper atom is pseudo-tetrahedrally co-ordinated by two nitrogen atoms, one from each base, and two bridging iodine atoms. Complex (5) crystallizes in two distinct monoclinic phases, both with space group C2/c and Z = 4. For the Q phase, a = 8.431 (4), b = 14.018(8), c = 13.019(7) A, and p = 96.19(5)"; R = 0.036 for 1 127 ' observed ' reflections. For the p phase, a = 16.060(22), b = 7.394(4), c = 14.715(10) A, and p = 119.70(4)"; R = 0.026 for 1 679 reflections. The two phases differ in their mode of packing of discrete monomeric [Cul(2,6Me2-py),] molecules; the copper atom is three-co-ordinate in each case with a planar environment. In the a phase, Cu-N,I are 1.984(5) and 2.682(2) A respectively with N-Cu-I,N 105.2(1) and 149.6(2)"; ir; the p phase Cu-N,I are 1.984(4) and 2.642(2) A and N-Cu-I,N 108.26(8) and 143.5(1)". The adoption of the unusual three-cordination about the copper is ascribed to the steric crowding caused by the substituents in both the 2 positions of the base. | |