12538-96-4Relevant articles and documents
Thermal stability and kinetics of ylide-borane complexes
Stoddard, Jonathan M.,Shea, Kenneth J.
, p. 149 - 155 (2008/10/09)
Complexes of dimethylsulfoxonium methylide (1) and organoboranes are crystalline for ylide·BH3 (2), ylide·BPh3 (3), ylide·B(C6F5)3 (4), and ylide·BF3 (5). These complexes undergo exothermic rearrangement by 1,2-migration upon heating to produce homologated organoboranes and dimethylsulfoxide. Non-isothermal kinetic analysis of the differential scanning calorimetry (DSC) data for ylide·BPh3 (3) and ylide·B(C6F5)3 (4) complexes was applied using the Flynn-Wall-Ozawa and Kissinger methods. The calculated apparent activation energy for the reaction of ylide·BPh3 (3) yielded consistent results between the A1.5 model (Ea=120 kJ mol-1, A=4.79×1013 min-1) and Kissinger method (Ea=129 kJ mol-1, A=1.73×1017 min-1). The analysis for the reaction of ylide·B(C 6F5)3 (4) gave consistent results between R2, R3, and F1 models with the average parameters, Ea=262 kJ mol-1, A=3.33×1033 min-1. The Kissinger analysis for the reaction of ylide·B(C6F5)3 (4) gave Arrhenius activation parameters (Ea=171 kJ mol-1, A=7.80×1019 min-1) that were higher than for the reaction of ylide·BPh3 (3). The kinetic data revealed that the C6F5 electron-deficient group has a higher activation energy for 1,2-migration and a higher entropy of activation for 1,2-migration than the C6H5 group. HF/6-31G(d) ab initio calculations agree with the kinetic data.
