Solid-Gas Hydrogenation of Hex-3-yne and 1,4-Cyclohexadiene in the Presence of the Clusters Ru₃(CO)₁₂, H₄Ru₄(CO)₁₂, H₂Ru₄(CO)₁₃, and H₂FeRu₃(CO)₁₃ Supported on Inorganic Materials. Infrared Evidence for Surface Organometallic Reactions

The clusters Ru₃(CO)₁₂ (1), H₄Ru₄(CO)₁₂ (2), H₂Ru₄(CO)₁₃ (3), and H₂FeRu₃(CO)₁₃ (4) supported on pyrex borosilicate glass behave as catalysts for solid-gas hydrogenation reactions of hex-3-yne and 1,4-cyclohexadiene. Their activity and selectivity are discussed. Ru₃(CO)₁₂ (1) was also supported on inorganic oxides, normally used as chromatographic materials or supports for heterogeneous catalysis and characterized by different acidities and surface areas. The observed activities depend on the nature of the inorganic supports; the presence of water also has some influence. Some of these materials were characterized by HRTEM microscopy. Organometallic products have been collected after the catalytic runs both when pyrex and inorganic oxides were used as supports. In particular, the "surface organometallic reactions" of Ru₃(CO)₁₂ and H₄Ru₄(CO)₁₂ supported on silica have been followed by IR spectroscopy. The nature and role of the arising organometallic compounds are discussed. Our solid-gas results are in good agreement with the mechanisms previously proposed for the hydrogenation of comparable substrates under homogeneous conditions.