Nickel borides promoters

Nickel, either as a Raney catalyst or in the form of nickel boride, is also effective in the reduction of the C=0 bond. An increase in the catalytic activity can be brought about by metal promoters (chromium and molybdenum). Copper chromite may also be used. 

Fig. 12.2. The promoting effect of adding chromium to the P-1 nickel boride catalyst in the hydrogenation of various substrates.

Hydrogenation Copper chromite (Lazier catalyst). Copper chromium oxide (Adkins catalyst). Lindlar catalyst (see also Lithium ethoxyacetylide, Malealdehyde, Nickel boride). Nickel catalysts. Palladium catalysts. Palladium hydroxide on carbon. Perchloric acid (promoter). Platinum catalysts. Raney catalysts, Rhenium catalysts. Rhodium catalysts. Stannous chloride. Tributylborane. Trifluoroicetic acid, Tris (triphenylphosphine)chlororhodium. 

Although palladium occupies the dominant position in semi-hydrogenation catalysts, it is by no means the only metal suitable for formulation into a viable catalyst. Mention has already been made of the nickel boride alternatives, with or without copper promotion, for example. Other examples include the skeletal catalyst Raney nickel [69], alumina-supported nickel [70], and aluminum phosphate-supported nickel [71] (Eqs 21 and 22) ... 

The reduction of nitroarenes to azoxy compounds ArN=N(0)Ar is promoted by bismuth tiichloiide/powdered zinc. Aromatic amines are formed in excellent yields in the reduction of nitroarenes with BH3/NiCl2 or nickel boride . Acyl, ester, amide and cyano groups are not affected. Reaction of the nitro compounds RCH2NO2 (R = Ph, Bz... 

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