Transition-metal Schiff Base complexes. Part III. Nickel complexes derived from pyrrole-2-carbaldehyde and aliphatic and aromatic diamines

Abstract

A series of planar, diamagnetic, nickel complexes, derived from pyrrole-2-carbaldehyde, and 1,2-diaminobenzene, 1,2-diaminonaphthalene, 1,2-diamino-ethane and -propane, 1,2-diamino-(2-methyl)propane, 1,3-diaminopropane, and DL- and meso-2,4-diaminopentane, have been characterised by electronic, mass and proton magnetic resonance spectroscopy. A palladium complex derived from 1,3-diaminopropane is also described. A complete assignment of all resonances in the ¹H n.m.r. spectra of each complex is given, and the conformation of the group bridging the two pyrrolyl residues in the complexes derived from 1,2-diaminopropane and DL-2,4-diaminopentane has been established in solution. The complexes were examined by polarography and cyclic voltammetry and were shown to undergo one reduction process; only in the species derived from 1 3-diaminopropane and DL-2,4-diaminopentane was this wave reversible.