Diborane boron exchange

The compound is thermally unstable at room temperature and has an extrapolated boiling point of 27°. Boron exchange is observed with diborane(6) enriched in boron-10 109) and the SH proton exchanges with deuterium chloride 109>. The presence of the mercapto-group in the bridging position is unequivocally established by the boron-11 nmr... 

BCl, BBr, and BI undergo exchange reactions to yield mixed boron hahdes. Exchange reactions also occur with trialkyl, triaryl, trialkoxy, or triaryloxy boranes and with diborane. Anhydrous metal bromides and iodides can be prepared by the exchange reaction of the metal chloride or oxide and BBr or BI (21)-... 

No eleven-vertex arachno species is known, but BjoHig" (III- and IV-NIO) 129, 132) in the presence of diborane indulges in total boron and hydrogen exchange, and a transient arachno intermediate BuHie has been suggested 124). 

A study of the exchange of boron between isotopically normal diborane and 10B-enriched diborane (273) showed that exchange is quite rapid at room temperature, the rate being of the same order of magnitude as the... 

Bis(dimethylamino)borane may be prepared by the reduction of CIB[N(CH3)2]21 or by gas-phase exchange of hydride and dimethylamino groups on boron.2,3 The latter method, using diborane(6) and excess B[N(CH3)2]3 and described here, is the most convenient for the synthesis of a few millimoles of product. The basic vacuum-line techniques necessary to carry out this synthesis are detailed in reference 4. 

Exchange reactions are common between boron halides and alkyl or aryl snbstitnents, other halides, alkoxy and aryloxy gronps, and diborane. Some examples are shown in Scheme 2. 

There are relatively few examples of formation of boron-carbon bonds in compounds containing preformed boron-boron fragments. The preparation of dibutylbis(dimethylamino)diborane(4) by alkyl-amino exchange has been noted (77). 

The isoelectronic boron analog BHC cation has a similar symmetry (31) According to the latest calculations by Olah and Rasul, protonation of BH3 to BIT is strongly exothermic by 154.4kcalmol T This indicates that hydrogen-deuterium exchange in diborane in superacids can also involve monomeric BH3 [Eq. (5.10)] ... 

Trialkyl alanes may be used, like boron hydride derivatives (e.g., tetraalkyl diboranes), as catalysts for the alkyl exchange between two different trialkyl boranes (133). The A1R3 compounds are particularly suitable for bringing about the disproportionation of mixed dialkylalkenyl boranes (e.g., diethylalkenyl boranes), which result from the partial hydro-boronation of dienes with tetraethyldiboranes under the mildest possible... 

Exchange reactions of alkylated diboranes with higher boron hydrides are discussed in Sections II,B>1 and II,D. 

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