g- and a-tensor calculations in the zero-order approximation for relativistic effects of Ni complexes Ni(mnt)(2)(-) and Ni(CO)(3)H as model complexesfor the active center of [NiFe]-hydrogenase

Fully relativistic calculations in the zero-order regular approximation (ZO RA) for relativistic effects were performed for the inorganic complexes bis (maleonitriledithiolato)nickelate(III) (Ni(mnt)(2)(-)) and nickeltricarbony lhydride (Ni(CO)(3)H). They have some similarities with the active center o f the [NiFe] hydrogenase. The influence of scalar-relativistic (SR) effects on the structural parameters are discussed. For both complexes, magnetic r esonance parameters (g-, hyperfine, and quadrupole tensors) are obtained. T he deviation of the calculated g-tensor values from the experimental data i s proportional to the deviation from the free electron value. The agreement between calculated and experimental hyperfine tensors for transition metal s is very good when scalar-relativistic (SR) effects and spin-orbit (SO) co upling are considered. The isotropic hyperfine interaction is taken from SR unrestricted calculations and the anisotropic part from SR and SO spin-res tricted calculations. The relativistic effects are not so large for the lig hter ligand atoms.