STEREOCHEMISTRY AND PROTON RESONANCE STUDY OF BIS[3-(N-SUBSTITUTED AMINO)METHYLENECAMPHORATO]NICKEL(2) COMPLEXES

A series of bis[3-(N-substituted amino)methylenecamphorato]nickel(II) complexes has been prepared by a nonaqueous method. The stereochemistry of the complexes in solid and solution phases has been investigated in order to evaluate the influence of intramolecular steric interactions on the relative stabilities of the planar and tetrahedral configurations. In the solid phase, depending upon the nature of the amine substituent R, the complexes are either diamagnetic and planar or tetrahedral with magnetic moments > 3 BM. In chloroform solution the complex with R = H is planar; complexes having R = aryl or isopropyl are tetrahedral; and those with R = methyl, ethyl, or benzyl are involved in a planar ↔tetrahedral equilibrium. The paramagnetic complexes exhibit well-resolved isotropic pmr shifts, and some of the resonance signals may be assigned with certainty. The temperature dependence of pmr shifts of several complexes was measured, meso and active diastereomers were detected by pmr for a complex prepar d from racemic ligand. Split resonance signals observed for several other complexes are believed to result from restricted rotation of the R group. A brief comparison of these complexes with several other series of complexes involved in the planar→ tetrahedral equilibrium is given. © 1969, American Chemical Society. All rights reserved.