Borohydride salts

Shore, S. G., and R. W. Parry Chemical Evidence for the Structure of the Diammoniate of Diborane , III. The Reactions of Borohydride Salts with Eithium Halides and Aluminium Chloride. J. Amer. chem. Soc. 80, 12 (1958). 

Other reducing agents may be used, and the borohydride salt Na eBH3(CN) is convenient to use in place of H2 and a metal catalyst. 

As might be expected, the course of the reaction is profoundly altered by inclusion of a lithium cation in the treatment of the complete borohydride salt. Ab initio calculation (Bonaccorsi et al., 1982) shows that LiBH4 in the gas phase is a tightly bound ion pair. The initial step of its reaction with formaldehyde or acetone involves coordination of the lithium to the carbonyl oxygen to give a complex with a linear C=0 Li- B array, at — 210 kJ mol-1 relative to reactants. This does not dissociate to BH 4 and... 

Synthesis. The [PFe ] complexes are most conveniently prepared by reduction of the corresponding Fe porphyrins in the absence of potential axial Ugands using either chromium(II) complexes, aqueous dithionite under vacuum, " sodium amalgam, borohydride salts, or zinc amalgam in aprotic organic solvents. Using aqueous sodium dithionite or Zn/Hg an Fe(II) porphycene complex, namely the Fe(II) complex of 2,7,12,17-tetra-n-propylporphycene [(TprPc)Fe ] has also been synthesized by... 

The reaction of metal halides with borohydride salts constitutes a general route to transition metal borohydrides.11 Further, in the presence of Lewis bases, borohydrides may be converted into metal hydrides which, depending on the metal, may lose dihydrogen thereby... 

The thermal decomposition of a variety of tetramethylammonium salts of weak bases has been studied and the major product is generally the methylated anion 92>. The temperature required to decompose the bromide and chloride salts to trimethylamine and the methyl halide is near 360 °C and the products recombine on cooling. The fluoride salt decomposes at a much lower temperature (180 °C) and the products do not recombine 92>. Decomposition of the borohydride salt at 225 °C gives trimethylamine borane and methane 11h... 

Light induced electron transfer from an amine to an excited arene leading to a contact radical ion pair is proposed to account for the products observed when 9,10-dicyanoanthracene is irradiated in wet benzene in the presence of an a-aminoketone. The non-polar solvent maintains the proximity of the radical ion pair which would normally then undergo non-productive back electron transfer however, in this case the ion pair reacts, ultimately to furnish 9,10-dihydro-9,10-dicyanoanthracene along with products of fragmentation of the a-aminoketone. Alkyl borate and borohydride salts can also serve as electron donors in the photoreduction of aryl cyanides and aryl halides and an abstract of a report on this topic has appeared. ... 

Metal borohydride salts are simple and practical reagents that are widely used in modern synthesis, in both academic and industrial settings. As such, they are widely available from most commercial chemical vendors and are typically inexpensive. 

Methods of preparation of phosphine boranes include the reaction of phosphines with diborane (9.7), the addition of boron trihalides to phosphines (9.8) and the action of heat on certain arylphos-phonium borohydride salts (9.9). Phosphines and phosphites rupture trialkylamine borane complexes, replacing B-N with B-P. 

Borohydride salts react with trivalent phosphorus compounds to give a variety of boranes, phosphines and phosphine-borane adducts (9.20-9.23). The reaction between sodium borohydride and phosphorofluoridic acid produces diborane in about 80% yield, and is a convenient method of preparation of the latter. 

The BH stretch in borazines absorbs at 2580-2450 cm Compounds where the boron octet is complete such as in borohydride salts or amine-borane coordination complexes absorb at 2400-2200 cm due to BH stretch. 

Parry, R. W. Shore, S. G., Chemical evidence for the structure of the diammoniate of diborane. III. The reactions of borohydride salts with lithium halides and aluminum chloride, J. Am. Chem. Soc. 1958, 80, 15-20. 

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