| This thesis focuses on the mechanistic investigation of catalytic carbon-carbon sigma- bond hydrogenation of hydrocarbons using water as the convenient hydrogen source under neutral conditions by group 9 metalloporphyrins M(por)X.;The benzylic carbon-carbon bond of [2.2]paracyclophane (PCP) was catalytically hydrogenated to give 4,4¡¦-dimethylbibenzyl up to 98% yield using water with 10 mol% M(ttp)X pre-catalyst (ttp = 5,10,15,20-tetratolylporphyrinato dianion, M = RhIII and IrIII, X = Me, Bn and iPr) at 200 °C in C6D6. Deuterium labeling experiments using D2O supported water as the hydrogen source. Preliminary screening with CoII(ttp) catalyst in polar DMF solvent at 220 °C also yielded the hydrogenation product selectively. The role of DMF is proposed to promote the hydrolysis of cobalt(III) porphyrin benzyl intermediates and increase the solubility of H2O. [Special characters omitted].;Kinetic studies on the stoichiometric benzylic CCA of PCP with Rh II(tmp) metalloradical (tmp = 5,10,15,20-tetramesitylporphyrinato dianion) gave the rate law as rate = k[RhII(tmp)] 2[PCP]. The 2nd order dependence on RhII(tmp) radical suggests a bi-metalloradical CCA mechanism via a four-centered transition state. [Special characters omitted].;In the iridium catalyzed system, IrIII(ttp)H was found to have promoting role in the hydrogenation process. The bi-molecular reductive elimination between IrIII(ttp)H and the CCA intermediates speeded up the hydrogenation process. It is estimated that this process gave the hydrogenated alkyl fragment 3 times faster than hydrolysis of the CCA intermediates. [Special characters omitted]. |
