Boron-hydrogen complex

Methane sulfonic acid, trifluoroacetic acid, hydrogen iodide, and other Brmnsted acids can faciUtate 3 -acetoxy displacement (87,173). Displacement yields can also be enhanced by the addition of inorganic salts such as potassium thiocyanate and potassium iodide (174). Because initial displacement of the acetoxy by the added salt does not appear to occur, the role of these added salts is not clear. Under nonaqueous conditions, boron trifluoride complexes of ethers, alcohols, and acids also faciUtate displacement (87,175). 

Elimination of hydrogen chloride from 2/f perfluoro-2-methylpropane-1 -sulfenyl chloride by the triethylamine-boron trifluoride complex results in cyclization to perfluoro-l,l-dimethylthiirane (perfluoroisobutylene sulfide) [, 9] (equation 9)... 

Rather than continue to progress from less complex to more complex boron-hydrogen compounds, it will be more convenient to jump to a complex but highly symmetric borohydride ion. lB,H 2f. It may be synthesized bv the pyrolvsis of the BjHJ ion ... 

Elimination of hydrogen fluoride from vinylic fluoride 16. using the triethylamine-boron trifluoride complex, yields the allene 17.96... 

In some metallacarbaborane clusters, a metal fragment is supported on the outside of the carbaborane skeleton, typically by B H M interactions, for example, complex (27) involves exo interactions between the T1(I) atom of one cage and two terminal boron hydrogen bonds of a second cage. The exo descriptor illustrates the relationship of the metal fragment to the carbaborane and the nido descriptor classifies the carbaborane cage. 

Related catalytic studies were performed recently by Kameo and Nakazawa on bisphosphine-borane Rh and Ir complexes (Scheme 13). Accordingly, transfer hydrogenation of ethyl phenyl ketone could be successfully achieved with the Rh complex 29 at 70°C in the absence of any base. Complexes featuring M B interactions proved significantly less active. Comparison with the related boron-free complex 45 highlights the important and beneficial influence of M—H—B bridging interaction. 

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