Tetraphenylborate salts of some tridentate chelates of nickel(II)

Abstract

Tetraphenylborate salts of nickel(II) complexes have been prepared where the nickel(II) is bound to the tridentate Schiff base adducts of unsymm.- N,N-dimethyl or - N,N-diethylethylenediamine and the β-dicarbonyl compound, CH 3COCHRC(O)H, R = CH 3CO or C 2H 5OCO or 2-acetyl-5,5-dimethyl-1,3-cyclohexanedione. The synthesis involves reacting the chloro or bromo derivatives of the tridentate nickel(II) complexes with sodium tetraphenylborate in dichloromethane. Replacing the halo ligand by the noncoordinating tetraphenylborate ion results in some unusual coordinate bonding. For the CH 3COCHRC(O)H tridentate ligands, a dinuclear +1 cation is formed with two tridentate-nickel(II) groups bound to one another by a bridging hydroxyl ligand. For 2-acetyl-5,5-dimethyl-1,3-cyclohexanedione in the solid state, the free carbonyl of a tridentate ligand bound to a nickel(II) ion occupies the fourth coordinate site of a second nickel(II) ion. In acetone solution, the fourth coordinate position is believed to be occupied by the solvent.