Nickel and copper complexes based on tridentate nitrogen donor ligand 2,6-bis-(1-phenyliminoethyl) pyridine: synthesis, spectral and structural characterization

The reaction of CuCl2•2H2O with 2,6-bis(1-phenyliminoethyl)pyridine (referred hereafter as L) in 1:1 molar ratio in methanol or acetronitrile at room temperature afforded distorted trigonal-bipyramidal complex [Cu(κ3-L)Cl2]. On the other hand, the reaction of NiCl2•6H2O with 2 equivalents of L gave an octahedral complex [Ni(κ3-L)2]2+, which was isolated as [Ni(κ3-L)2][BF4]2 using NH4BF4. The complexes have been characterized by elemental analyses, FAB-MS, IR, EPR and electronic spectral studies. Molecular structures of both the [Cu(κ3-L)Cl2] (1) and [Ni(κ3-L)2](BF4)2 (2) have been determined by single crystal X-ray analyses. Weak interaction studies on 1 and 2 revealed stabilisation of the crystal packing by inter and intra-molecular C–H⋯X (X=F, Cl, π) interactions. In complex 2 ortho C–H bond from phenyl rings leads to unexpected C–H⋯π interaction with nickel α,α′-diimine chelate ring. This provides structural support for metalloaromaticity in the chelate ring of complex 2