Crystal chemistry of the 4,4 '-dimethyl-2,2 ' bipyridine/copper bromide system

The reaction of 4,4 ' -dimethyl-2,2-bipyridine (henceforth dmbp) with coppe r(I) and/or copper(II) bromide under a wide variety of conditions has led t o the isolation of 10 different crystalline materials. These include one Cu (I) salt, [Cu(dmbp)(2)]Br (a distorted tetrahedral Cu species and a lattice Br- ion); two mixed valence Cu(I,II) compounds, [Cu(dmbp)(2)Br][CuBr2] (di screte 5-coordinated Cu(II) and linear Cu(I) species) and Cu(dmbp)(2)BrCu2B r3 (linked 5-coordinate Cu(II) and trigonal planar Cu(I) species); and seve n Cu(II) compounds, (dmbp)CuBr2 (stacked planar monomers), [(dmbp)CuBr2](2) (five coordinate bibridged dimers), (dmbp)Cu2Br4 (stacked planar bibridged dimers), (dmbp)CuBr2(DMSO) (five coordinate monomers), [Cu(dmbp)(2)Br]OH . 51/2H(2)O and [Cu(dmbp)(2)Br](Br/OH). 51/2H(2)O (five coordinate monomers), and (dmbpH(2))CuBr4.H2O (distorted tetrahedral monomers). The crystal stru cture determinations of these materials are reported. A common thread in th eir structural chemistry is the supramolecular architecture developed throu gh interdigitation of the dmbp rings on neighboring molecular species. The interdigitation leads to layer structures in many of the materials. The dis tances between the interdigitated dmbp rings are in the range 3.4-3.7 Angst rom. The Cu(dmbp)(2)Br+ species exhibits an exceptionally large distortion from tetrahedral geometry due to deviation of the dihedral angle between th e mean planes of the Cu(dmbp) fragments from 90 degrees. The Cu(dmbp)(2)Br cations have distorted trigonal bipyramidal geometry, the Br- ion occupyin g an equatorial position. The length of the Cu-Br bond in the Cu(dmbp)(2)Br + species is correlated with the change in dihedral angle between the plane s of the two dmbp ligands. The mono-dmbp complexes show a greater variation in coordination geometry for the Cu(II) species, including distorted trigo nal bipyramidal and augmented square planar 4 + 1 and 4 + 2 coordination.