The First 2-Electron-2-Proton Transfer

In view of the protonation and reduction process it is instructive to compare results for Fe(II) compounds with the corresponding data for the positively charged Fe(III) analogues. Iron and ruthenium complexes with two metal centers should be investigated. While the iron complexes model particular features of the FeMo-cofactor in nitrogenase, the ruthenium analogues are analyzed because of their 

First Step Hydrogen Bonds in Mononuclear Fe(II) Complexes 

We investigated (82) two iron sulfur complexes with diazene (di-imide) as the sixth ligand, [Fe(NHS4)(N2H2)] = 1 (N2H2) and [Fe(S4)PR3 (N2H2)] = 2(N2H2)(Fig.3). 

Among these diazene complexes, the dinuclear analogue of 1(N2H2), [p-N2H2 Fe(NHS4) 2], is the first example in which diazene binds to low-spin Fe(TI) centers carrying only biological compatible donor atoms (see also Section IV. C). 

We chose two model compounds which differ considerably in their coordination spheres (82) and, therefore, are supposed to react in qualitatively different ways. The ligand sphere of 1(N2H2) consists of one chelate ligand with four in-plane sulfur atoms. Thus, two different sulfur functionalities are involved in the coordination of the Fe(II) 

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