Kinetics and mechanism of hydroboration reactions of HBBr2·SMe2 and HBCl2·SMe2 – Application of 11B NMR spectroscopy

Change in mechanistic pathway of hydroboration: A detailed kinetic study of H2BBr·SMe2 and HBBr2·SMe2

“…varying Lewis acid character as well as the number of hydroboration sites. The outcome of this work, along with that of HBBr 2 AESMe 2 reported earlier [22], show that hydroboration mechanism of the mono-and di-bromoborane dimethyl sulfide complexes is different.…”

“…We recently reported a detailed kinetic and mechanistic study for hydroboration of 1-octene with HBBr 2 AESMe 2 and HBCl 2 AESMe 2 [22]. The activation parameters, especially DS 6 ¼ , support the dissociation of Me 2 S from the boron centre prior to hydroboration, which itself is an associative process.…”

“…Nonetheless, not much with regard to the kinetics and the mechanism H 2 BBrAESMe 2 exists. As it has been highlighted in our previous papers [22,23], the necessity to pursue detailed mechanistic studies on hydroboration is crucial for the commercialisation of a boron based cyclic process [23], through which high commercial value alpha olefins can be produced from internal olefins. This cycle involves three steps, namely hydroboration, isomerization and displacement or dehydroboration.…”

“…Kinetic and mechanistic studies on each of these steps will provide valuable information such as specific rate constants, enthalpy, entropy and physical data in general. At present, the unavailability of this information can be attributed to the inadequacies incurred from the method of analysis, namely GC, which had all along been used in studying the kinetics of hydroboration reactions [22].…”

“…The efficiency of modern spectroscopy, especially IR as well as 11 B NMR in the kinetic and mechanistic monitoring of reactions involving addition complexes of boron, has in recent time allowed for some advance in this field [22][23][24]. However, to date, thorough kinetic studies on hydroboration reactions of H 2 BXAELB as well as specific and accurate mechanistic information thereof, have not been documented.…”