关键词: 铁络合物, 固氮酶, 电子传递, 化学键, 簇状化合物, 电子结构, 从头计算法, 还原反应, 分子轨道理论, 硫络合物

Ab initio calcns. on Fe2S2Cl42- were carried out. This kind of 2Fe cluster has been the subject of extensive investigations because of electron-transport and catalytic functions of Fe-S proteins. Previous EH and SCF-SW-Xa calcns. showed that: (1) the highest occupied orbitals are mainly Fe 3d; and (2) the bridged S atoms are much more important than terminal ligands for binding, which are doubted by the recent SCF-SW-Xa-VB solution The present calcns. confirm that the occupied 3d orbitals are not frontiers but are located below the S and Cl lone-pair levels. The atomic populations indicate that Fe atoms behave as donors for 4s electrons rather than acceptors of 3d electrons. Moreover, both the S and Cl atoms are p-acceptors with a negligibly small difference.

Key words: IRON COMPLEX, NITROGENASE, ELECTRON TRANSFER, CHEMICAL BONDS, CLUSTER COMPOUND, ELECTRONIC STRUCTURE, AB INITIO CALCULATION, REDUCTION REACTION, MOLECULAR ORBITAL THEORY, SULFIDE COMPLEX