Co-ordination chemistry of 1,4-bis(o-aminobenzyl)-1,4-diazacyclohexane (L) with nickel(II), copper(II) and palladium(II)
Abstract
1,4-bis(o-aminobenzyl)-1,4-diazacyclohexane (L) has been synthesized and its co-ordination chemistry with nickel(II), copper(II) and palladium(II) investigated. The reaction of L with Ni(ClO4)2·6H2O in a chloroform–ethanol mixture affords orange, diamagnetic [NiL][ClO4]21 which consists of the square-planar dication [NiL]2+ in the solid state and in weakly or non-co-ordinating solvents (nitromethane, acetone). In co-ordinating solvents (acetonitrile, pyridine, dimethylformamide) or in the presence of co-ordinating anions (NCS–) blue solutions of 1 are obtained from which blue, paramagnetic species were isolated as crystalline materials: [NiL(NCS)2]2 and [NiL(MeCN)2][ClO4]2·1.5 MeCN 3. Complex 2 was shown by X-ray crystallography to consist of neutral, octahedral [NiL(NCS)2]. Using Ni(NO3)2·4H2O as starting material both square-planar, orange [NiL][NO3]24a and blue, octahedral [NiL(NO3)2]4b containing two monodentate NO3– ligands were isolated. Reaction of L with Cu(ClO4)2·6H2O and Cu(NO3)2·4H2O in CHCl3–EtOH produced blue crystals of square-planar [CuL][ClO4]25 and five-co-ordinate [CuL(H2O)][NO3]2·H2O 7, respectively. Recrystallization of 5 from MeCN produced blue crystals of [CuL][ClO4]2·2MeCN 6. Palladium(II) acetate reacts with L in CHCl3–EtOH affording orange-brown crystals of [PdL][ClO4]28. The crystal structures of 1, 2, 5, 7 and 8 have been determined by X-ray crystallography. In the solid state the ligand is always equatorially co-ordinated in a transoid fashion where one of the two [graphic omitted]aniline chelate rings adopts a boat and the other a twist-boat conformation. This has been corroborated by solid-state 13C cross-polarization magic angle spinning NMR spectroscopy of 1 and 8.