Nickel boride catalyst

[8] They are air-stable, non-magnetic and non-pyrophoric,[5] but slowly react with water to form nickel hydroxide Ni(OH)2.

[5] These catalysts originate during World War II with the work of a research group led by Hermann I. Schlesinger, discoverer of borohydrides.

They noted that reaction of NaBH4 with salts of certain transition metals yielded black precipitates, and that the cobalt product catalyzed the decomposition of borohydride.

[9] In 1951, Raymond Paul and others investigated the reaction of NaBH4 with nickel chloride, sulfate, and acetate in various solvents and measured their performance as hydrogenation catalysts.

Brown reported the synthesis and performance of two similar catalysts, which they denoted by "P-1" (the same as Paul's) and "P-2", obtained by reacting sodium borohydride with nickel acetate in water and ethanol, respectively.

[1] The P−1 catalyst can be generated by reacting a nickel(II) salt, such as sulfate, chloride, nitrate, or acetate, and sodium borohydride in alkaline aqueous solutions.

[5][3] The chemistry is very similar to that of electroless nickel-boron plating, and yields hydrogen gas and the corresponding sodium salt as byproducts.

[5] The P−2 form is prepared similarly from nickel(II) acetate and sodium borohydride in ethanol.

An X-ray diffraction analysis of P-1 by L. Hofer and others in 1964 indicated that the nickel and boron contents were in 2.5:1 ratio, but the solid contained 11% of strongly bound water and other compounds.

[1] For these reasons, P−1 is usually used for the complete reduction of unsaturated hydrocarbons under mild conditions, while P−2 is useful in partial reductions such as converting alkynes to alkenes in high yields:[13] The H2/Ni2B system will not hydrogenolyse ethers, alcohols, aldehydes, amines and amides as it reduces alkenes in preference, even under forcing conditions.

Since Ni2B is non-pyrophoric, stable in air, and give high yields in many cases, it is proposed as a safer alternative to Raney Nickel for removal of cyclic thioacetals.