Mono- and di-nuclear helical complexes of 2,2′:6′,2″:6″,2‴:6‴,2â�—-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]

Abstract

A series of substituted 2,2′:6′,2″:6″,2‴:6‴,2â�—-quinquepyridine ligands has been prepared and its coordination chemistry investigated. The presence of substituents on the ligand does not alter the coordination 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‴,2â�—-quinquepyridine][monoclinic, space group P2₁/a,a= 17.441(4), b= 11.765(4), c= 20.402(6)Å, β= 105.24(2)°, 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‴,2â�—-quinquepyridine][orthorhombic, space group Pnna, a= 16.916(17), b= 25.661(25), c= 16.054(14)Å, Z= 4, R= 0.086, R′= 0.088].