Nickel boride, and

Another highly active non-pyrophoric nickel catalyst is prepared by reduction of nickel acetate in tetrahydrofuran by sodium hydride at 45° in the presence of tert-amyl alcohol (which acts as an activator). Such catalysts, referred to as Nic catalysts, compare with P nickel boride and are suitable for hydrogenations at room temperature and atmospheric pressure, and for partial reduction of acetylenes to civ-alkenes [49]. 

Other reactive forms of nickel including nickel boride and nickel alkoxide complexes can also be used for desulfurization. Tri-w-butyltin hydride is an alternative reagent for desulfurization.204... 

Paul Buisson Joseph Ind. Eng. Chem. 1952,44, 1006 Brown Chem. Commun. 1969,952. J. Org. Chem. 1970, 35. 1900. For a review of reductions with nickel boride and related catalysts, sec Canem Osby Chem. Rev. 1986, 86. 

Tetrasubstituted viodinitro compounds have been converted to olefins by treatment with amalgamated calcium.3214 Various functional groups, such as CN and COOR, did not affect the reaction. Other reagents that have been used include sodium sulfide in DMF,32V nickel boride and ultrasound,330 Bu3SnH,331 and SnCI2.332 Radical-ion mechanisms are likely in all these cases. 

The hydrogenation of cyclopropenecarboxylic acids leads to good yields of the saturated acid. Two elegant routes to cis-chrysanthemic acids have been reported based on this process. In the first, the ester (249) is reduced by either diimide or nickel boride and hydrogen 49) ... 

Brown et al.18,19 and Brunet et al.20 studied the rates of hydrogenation of various olefinic compounds over P-1 and P-2 nickel borides and over a nickel catalyst designated Nic, obtained from NaH-f-PeONa-Ni(OAc)2, respectively, in ethanol at 25°C and 1 atm H2 (Table 3.1). Over P-1 Ni, the decrease in the rate of hydrogenation with 2-methyl-l-... 

TABLE 3.1 Rates of Hydrogenation of Alkenes over P-1 and P-2 Nickel Boride and Nic Catalysts... 

Unhindered simple olefins are usually rapidly hydrogenated under very mild conditions over platinum metal catalysts such as platinum, palladium, and rhodium as well as over active nickel catalysts such as Raney Ni, nickel boride, and Urushibara Ni. For example, 0.1 mol of cyclohexene is hydrogenated in 7 min over 0.05 g of Adams platinum oxide in ethanol at 25°C and 0.2-0.3 MPa H2 (eq. 3.1).5 1-Octene and cyclopentene (eq. 3.2) are hydrogenated in rates of 11.5 and 8.6 mmol (258 and 193 ml H2 at STP) g Ni 1-min 1, respectively, over P-1 Ni in ethanol at 25°C and 1 atm H2.18 Hydrogenation of cyclohexene over active Raney Ni proceeds at rates of 96-100 ml H2 at STP (4.3-4.5 mmol) g Ni min-1 in methanol at 25°C and 1 atm H2 49,50 and can be completed within a short time, although usually larger catalyst substrate ratios than required for platinum catalyzed hydrogenations are employed (eq. 3.3).50... 

Table 7 Desulfurization of Aromatic Sulfur Compounds by Nickel Boride and Raney Nickel ...

Nickel boride catalysts have been considered viable alternatives to Raney nickel since they are non-pyrophoric, are easily prepared and the preparation procedure is reproducible. In addition these catalysts appear to be somewhat more active than W2 Raney nickel for the hydrogenation of alkenes and nitriles but both types of catalyst have about the same activity for carbonyl group hydrogenation. While nickel boride and Raney nickel are both more resistant to... 

Clark et aid compared nickel boride and Raney nickel for desulfurization of... 

Monodisperse colloidal nickel boride and cobalt boride particles are synthesized by reducing, with NaBH4, the metallic ions solubilized in the water cores of the microemulsions. The NaBH4/MCl2 ratio was held equal to 3, because larger particles were obtained for a lower value, the particle size remaining constant above that ratio [2-4]. 

The F values for nickel boride and cobalt boride particles are quite different. For the former the value obtained for F is equal to 3.2 x 10 and for the latter, 17.4 x 10" As for these experiments, the rearrangement rate of the microemulsion system is constant in the first approximation, the difference between the F values probably being due to the different solvation of the two types of ions at the interface. The Co(II) ions contain, on average, one hexanol molecule in their first coordination shell, while the Ni(II) ions are multiply coordinated with hexanol at the interface. The mobility of the latter is hence lower, and the probability of collision between the two reduced Ni atoms required to form a nucleus is also lower. In other words, the rate of nucleation is higher for cobalt boride than for nickel boride particles. 

M-A Einarsrud, E Hagen, G Pettersen, T Grande. Pressureless sintering of titanium diboride with nickel, nickel boride and iron additives. J Am Ceram Soc 80 3013, 1997. 

Einarsrud, M., Hagen, E., Pettersen, G., Grande, T. (1997). Pressureless sintering of Titanium diboride with Nickel, Nickel Boride, and Iron additives. Journal of the American Ceramic Society, 80, 3013-3020. doi 10.1111/j.l 151-2916.1997. tb03227.x. 

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