Catalytic Alkyne Semihydrogenation with Polyhydride Ni/Ga Clusters.

The bimetallic, decanuclear Ni3Ga7‐cluster of the formula [Ni3(GaTMP)3(μ2‐GaTMP)3(μ3‐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 °C show that 2 consist of a mixture of a di‐ (2Di), tetra‐ (2Tetra) and hexahydride species (2Hexa). The structures of 2Di and 2Tetra 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. [ABSTRACT FROM AUTHOR]