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Download fileCalorimetric Study of the Activation of Hydrogen by Tris(pentafluorophenyl)borane and Trimesitylphosphine
journal contribution
posted on 2017-10-27, 00:00 authored by Adrian
Y. Houghton, Tom AutreyThe
mechanism of H2 heterolysis by the frustrated Lewis
pair of B(C6F5)3 and P(mes)3 was investigated by isothermal reaction calorimetry in the temperature
range from 30 to 90 °C. The experimental heat curves were modeled
in Berkeley Madonna to obtain both kinetic and thermodynamics data
simultaneously. The H2 activation reaction is treated as
a single, termolecular step with a rate constant of 0.61 M–2 s–1 at 303 K with an exothermic enthalpy of reaction,
ΔHH2 = −141 kJ/mol.
An Eyring analysis gave activation parameters of ΔH‡ = 13.6(9) kJ mol–1 and ΔS‡ = −204(85) J K–1 mol–1. Using D2 gas in place of H2 gas provided an opportunity to measure the relative rates
of D2 versus H2 heterolysis to yield a the kinetic
isotope effect, KIE = 1.1(1).