The azide and amide complexes (NBu4)[Ni(N3)('S3')] (2) and (NBu4)[Ni[N(SiMe3)2]('S3')] (4) were found to react with CO, CO2, and SO2 under very mild conditions at temperatures down to -50 degrees C. Depending on the N oxidation state of the nitrogen ligands, addition or partial to complete desoxygenation of the oxides takes place. The reaction between 2 and CO gives (NBU4)[Ni(NCO)('S3')] (3). The reactions between 4 and CO, CO2, and SO2 afford selectively the cyano, isocyanato, and sulfinylimido complexes (NBu4)[Ni(X)('S3')] with X = CN- (5), NCO- (3), and NSO- (6). The silyl groups act as oxygen acceptors. Mechanisms are suggested which have in common the formation of reactive five-coordinate (NBu4)[Ni(L)(L')('S3')] intermediates. In these reactions, highly activated L and L' react with each other. The complexes were characterized by standard methods, and (NBu4)[Ni(CN)('S3')] (5) was also analyzed by X-ray crystallography.

Charged but not changed: A trinuclear [NiFe] cluster combining the key structural features and reactivity of [NiFe] hydrogenases has been prepared (structure shown). Protons oxidize this cluster to its cation, which has the same structural parameters as the neutral form and therefore shows an important key feature of many oxidoreductases: structural rigidity during the electron‐transfer processes.

How do [NiFe] hydrogenases activate H(2)? Hydrogenases are key enzymes in the biological hydrogen and energy metabolism; the mechanism of H(2) activation, however, is unclarified. In particular, the oxidation states of the metals involved are discussed controversially. The title complex demonstrates that a distorted diamagnetic Ni(II) center and thiolate donors are sufficient (see picture) to catalyze the key reaction of hydrogenases, the H(2) heterolysis.

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How do [NiFe] hydrogenases activate H(2)? Hydrogenases are key enzymes in the biological hydrogen and energy metabolism; the mechanism of H(2) activation, however, is unclarified. In particular, the oxidation states of the metals involved are discussed controversially. The title complex demonstrates that a distorted diamagnetic Ni(II) center and thiolate donors are sufficient (see picture) to catalyze the key reaction of hydrogenases, the H(2) heterolysis.