Nickel borate

A variety of transition and other metal borates are reported in the literature. These include manganese borate, silver borate, iron borate, copper borate, nickel borate, strontium borate, lead borate, zirconium borate, double metal borates, and so on. Many of these borates have the potential to be flame retardants and/or smoke suppressants. 

Nickel Borates.—Several borates of nickel have been described. The tetraborate, NiO.4B2O3.10H2O, is obtained 2 by slow evaporation of a solution of nickel carbonate in boric acid. The precipitate first formed becomes crystalline gradually, yielding small brilliant and clear green crystals soluble in cold water, but becoming turbid at 40° C. 

Nickel borate has been recommended as a catalyst in the hydrogenation of unsaturated oils (see p. 95), but its action is attributable to nickel liberated by the hydrogen,6 and not to any inherent catalytic power of the borate itself.7 It offers no advantage over nickel oxide.8... 

Depending on the temperature, nickel borates can form crystals and glassy phases with different degrees of polymerisation, which are very often difficult to identify from the crystallographic point of view [66GME]. The numerous water-free and water-... 

So far no direct determination of thermodynamic data for water-free solid nickel borates has been reported in the literature. One of the reasons for this is probably the difficulty in obtaining well-defined crystalline phases. The only available data, published in a compilation of thermodynamic data for borate systems [74SLO/JON], are estimated values of the standard enthalpy of formation and the entropy for Ni0-2B203 at... 

The existence of at least one soluble nickel borate complex was postulated by Shchigol [61SHC]. Nickel orthoborate Ni(B02)2 4H20(s) dissolves better in orthoboric acid solutions than in pure water. The formation of the nickel borate complex in solution was believed to occur according to the reaction ... 

The dissociation constant of the aqueous nickel borate complex, according to Reaction (V.125), was calculated by Shchigol [61SHC], ) 3, (V.125) = 2.82x10 mol dm . 

SHC] Shchigol, M. B., Properties of cobalt and nickel borate, Zh. Neorg. Khim., 6, (1961), 2693-2703, in Russian, English translation in [61SHC2]. Cited on pages xxiv, 246, 247, 299, 300, 301. 

Dinca M, Surendranath Y, Nocera DG (2010) Nickel-borate oxygen-evolving catalyst that functions under benign conditions. Proc Natl Acad Sci US A 107 10337-10341... 

Cyclooctane-l,5-diyl-bis(pyrazol-l-yl)borate (L) with cobalt(II), nickel(II), and zinc(II) nitrates gives [(j -L)M] (M = Co, Ni, Zn) strongly stabilized by the C—H M agostic interactions, which justifies their inclusion in the class of organometallic complexes [89AGE205, 91ICA(183)203, 92IC974]. 

The poor efficiencies of coal-fired power plants in 1896 (2.6 percent on average compared with over forty percent one hundred years later) prompted W. W. Jacques to invent the high temperature (500°C to 600°C [900°F to 1100°F]) fuel cell, and then build a lOO-cell battery to produce electricity from coal combustion. The battery operated intermittently for six months, but with diminishing performance, the carbon dioxide generated and present in the air reacted with and consumed its molten potassium hydroxide electrolyte. In 1910, E. Bauer substituted molten salts (e.g., carbonates, silicates, and borates) and used molten silver as the oxygen electrode. Numerous molten salt batteiy systems have since evolved to handle peak loads in electric power plants, and for electric vehicle propulsion. Of particular note is the sodium and nickel chloride couple in a molten chloroalumi-nate salt electrolyte for electric vehicle propulsion. One special feature is the use of a semi-permeable aluminum oxide ceramic separator to prevent lithium ions from diffusing to the sodium electrode, but still allow the opposing flow of sodium ions. 

Colour centres in alkali borate glasses containing cobalt, nickel and copper. R. Juza, H. Seidel and J. Tiedemann, Angew. Chem., Int. Ed. Engl., 1966, 5, 85-94 (44). 

The family of poly(pyrazol-l-yl)borates has been widely used as supporting ligands in nickel coordination chemistry.556,557 Complex (191) is an example, where unusual cysteine coordination is achieved at a tris(pyrazolylborate)nickel(II) template.601 (191) undergoes rapid reaction with molecular oxygen to presumably form a sulfinate. 

Properties of nickel poly(pyrazol-l-yl)borate complexes such as solubility, coordination geometry, etc., can be controlled by appropriate substituent groups on the pyrazol rings, in particular in the 3- and 5-positions. Typical complexes are those of octahedral C symmetry (192)°02-604 and tetrahedral species (193). In the former case, two different tris(pyrazolyl)borate ligands may be involved to give heteroleptic compounds.602,603 Substituents in the 5-position mainly provide protection of the BH group. Only few representative examples are discussed here. 

This complex is not the actual catalyst for the hydrovinylation, but needs to be activated in the presence of a suitable co-catalyst. The role of this additive is to abstract the chloride ion from the nickel centre to generate a cationic allyl complex that further converts to the catalytically active nickel hydride species. In conventional solvents this is typically achieved using strong Lewis acids such as Et2AlCl. Alternatively, sodium or lithium salts of non-coordinating anions such as tetrakis-[3,5-bis(trifluoromethyl)phenyl]borate (BARF) can be used to activate hydrovinylation... 

The Lewis acidity and reactivity of these alkyl aluminum cocatalysts and activators with Lewis basic polar monomers such as acrylates make them impractical components in the copolymerization of ethylene with acrylates. To address this shortcoming, Brookhart et al. developed well-defined cationic species such as that shown in Fig. 2, in which the counterion (not illustrated) was the now-ubiquitous fluorinated arylborate family [34] such as tetrakis(pentaflurophenyl)borate. At very low methyl acrylate levels the nickel catalysts gave linear copolymers but with near-zero levels of acrylate incorporation. 

At high potentials in the passive region, the imaging of nickel surfaces proves difficult owing to the formation of thick oxide layers." It was shown by Bhardwaj et that on polycrystalline iron in a borate electrolyte, oxide formation starts as patches on the surface that gradually fuse together to establish a surface oxide fihn. Also, clusters of the hydroxide were seen" on a polycrystalline iron surface obsaved by in situ STM and after potential cycles in an NaOH electrolyte. 

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