Catalytic Alkyne Semihydrogenation with Polyhydride Ni/Ga Clusters

The bimetallic, decanuclear Ni3Ga7-cluster of the formula [Ni-3(GaTMP)(3)(& mu;(2)-GaTMP)(3)(& mu;(3)-GaTMP)] (1, TMP=2,2,6,6-tetramethylpiperidinyl) reacts reversibly with dihydrogen under the formation of a series of (poly-)hydride clusters 2. Low-temperature 2D NMR experiments at -80 & DEG;C show that 2 consist of a mixture of a di- (2(Di)), tetra- (2(Tetra)) and hexahydride species (2(Hexa)). The structures of 2(Di) and 2(Tetra) are assessed by a combination of 2D NMR spectroscopy and DFT calculations. The cooperation of both metals is essential for the high hydrogen uptake of the cluster. Polyhydrides 2 are catalytically active in the semihydrogenation of 4-octyne to 4-octene with good selectivity. The example is the first of its kind and conceptually relates properties of molecular, atom-precise transition metal/main group metal clusters to the respective solid-state phase in catalysis.

Automated summary

The bimetallic Ni3Ga7-cluster can react with dihydrogen to form a series of hydride clusters 2. The mixture of di-, tetra-, and hexahydride species were identified in cluster 2 using NMR spectroscopy and DFT calculations. The cooperation of both metals is crucial for the high hydrogen uptake and catalytic activity of cluster 2.