Kinetics of −CH₂CH₂– Hydrogen Release from a BN-cyclohexene Derivative

Abstract

Complete −CH 2 CH 2 − dehydrogenation of 1,2-dimethyl-1,2-BN-cyclohexene (1) was achieved using a Pd/C catalyst in a gas-phase microreactor. Arrhenius analysis yielded an activation energy (E a ) of 10.3 ± 0.3 kcal mol −1 and a pre-exponential factor (A) of 2.2 ± 0.2 (log A), respectively. These terms reflect a lesser kinetic favorability in comparison to those determined for all-carbon dimethylcyclohexene (E a = 8.6 ± 0.3 kcal mol −1 , log A = 3.6 ± 0.1). Despite being isostructural and isoelectronic with a CC bond, the B−N bond of 1 thus appears to confer a different measure of activity with respect to Pd-catalyzed −CH 2 CH 2 − dehydrogenation.Communication pubs.acs.org/Organometallics

Recent Developments in Azaborinine Chemistry

“…Dehydrogenation is an important step in syntheses of 1,2‐azaborinine, as can be seen above. The kinetics for the process for 1,2‐dimethyl‐1,2‐azaborinine were studied in the gas phase using a Pd/C catalyst . It was determined that the activation energy for the complete dehydrogenation of the azaborinine is 10.3 ± 0.3 kcal mol –1 (cf.…”

“…The kinetics for the process for 1,2-dimethyl-1,2-azaborinine were studied in the gas phase using a Pd/C catalyst. [37] It was determined that the activation energy for the complete dehydrogenation of the azaborinine is 10.3 ± 0.3 kcal mol -1 (cf. 8.6 ± 0.3 kcal mol -1 for the all-carbon analogue), pointing to a deactivating effect of the BN fragment towards the dehydrogenation of the ring.…”

A comparison of hydrogen release kinetics from 5- and 6-membered 1,2-BN-cycloalkanes

“…23 Sequential hydride/proton addition to cyclic aminoborane 5–H 2 (ref. 24 ) furnishes a mixture of trans - and cis -5 ( Scheme 3 ). The major trans diastereomer could be isolated by recrystallization, and its structure was unambiguously confirmed by single crystal X-ray diffraction analysis.…”