MONONUCLEAR AND DINUCLEAR HELICAL COMPLEXES OF 2,2'/6',2''/6'',2'''/6''',2''''-QUINQUEPYRIDINE (QPY) AND ITS 4',4'''-DISUBSTITUTED DERIVATIVES - CRYSTAL AND MOLECULAR-STRUCTURES OF [CO(BCPQPY)(H2O)(MEOH)][PF6]2 AND [NI2(BMTQPY)2(O2CME)][PF6]3 [BCPQPY AND BMTQPY = BIS(P-CHLOROPHENYL) AND BIS(METHYLTHIO) DERIVATIVES]

A series of substituted 2,2':6',2'':6'',2''':6''',2'''-quinquepyridine ligands has been prepared and its co-ordination chemistry investigated. The presence of substituents on the ligand does not alter the co-ordination chemistry, and double-helical complexes of 2:2 metal: ligand stoichiometry are obtained with nickel(II) and copper. Cobalt(II) can form either 1 :1 or 2:2 solid-state species, but in solution only mononuclear seven-co-ordinate complex ions are present. The crystal and molecular structures have been determined for the mononuclear complex [Co(bcpqpy)(H2O)(MeOH)][PF6]2 [bcpqpy = 4',4'''-bis(p-chlorophenyl)-2,2':6',2'':6'',2''':6''',2''''-quinquepyridine] [monoclinic, space group P2(1)/a,a = 17.441 (4), b = 11.765(4), c = 20.402(6) angstrom, beta = 105.24(2)-degrees, Z = 4, R = 0.085, R' = 0.0766] and the double-helical complex [Ni2(bmtqpy)(O2CMe)][PF6]3 [bmtqpy=4',4'''-bis(methylthio)-2,2':6',2'':6'',2''':6''',2'''-quinquepyridine] [orthorhombic, space group Pnna, a = 16.916(17), b = 25.661(25), c = 16.054(14) angstrom, Z = 4, R = 0.086, R' = 0.088].