METAL ISOTOPE EFFECT ON METAL-LIGAND VIBRATIONS: V. CIS AND TRANS Ni(II) PHOSPHINE-HALIDE COMPLEXES

Abstract
Infrared spectra (4000–200 cm−1) have been reported for Ni(DPE)X2 where X is Cl, Br and I and DPE is 1,2-bis(diphenylphosphino)ethane. The Ni[sbnd]X and Ni[sbnd]P stretching bands have been assigned based on the observed isotopic shifts due to the 58Ni-62Ni substitution. The Ni[sbnd]X stretching frequencies are always lower and the Ni[sbnd]P stretching frequencies are always higher in the cis-complexes such as Ni(DPE)X2 than in the corresponding trans-complexes such as Ni(PEt3)2X2. These differences between cis and trans configurations have been attributed to the strong trans-effect of phosphine ligands.