Oxidation and reduction of carbon monoxide and methane carbon-hydrogen bond activation: Molecular orbital theory

Calculations with the atom superposition and electron delocalization molecular orbital (ASED-MO) theory show that CO reacts readily with surface O on ZnO to form CO{dollar}sb2{dollar} which can immediately bind to O{dollar}sp{lcub}2-{rcub}{dollar} to form surface carbonate.; Co is attracted to a coadsorbed Al atom on Ni(111) surfaces, forming a non-linear Al-OC-Ni complex with low vibrational frequency. When trapped in Ni matrices CO again exhibits a large decrease in vibrational frequency. Our calculations show this is due to an interstitial defect structure where Ni atoms contact both C and O ends and back-donate to the empty {dollar}pi{dollar}* orbitals.; Theoretical evidence is given that OCH{dollar}sb3{dollar}, which is known to spill over from supported Ni and Pt to the alumina support, moves as an anion, OCH{dollar}sbsp{lcub}3{rcub}{lcub}-{rcub}{dollar}, from one Al{dollar}sp{lcub}3+{rcub}{dollar} site to another, paired with a proton which moves from one O{dollar}sp{lcub}2-{rcub}{dollar} site to another.; O{dollar}sp{lcub}-{rcub}{dollar} hole centers produced by charge transfer photoexcitation in W{dollar}sb{lcub}10{rcub}{dollar}O{dollar}sbsp{lcub}32{rcub}{lcub}4-{rcub}{dollar} abstract H from alkanes as do O{dollar}sp{lcub}-{rcub}{dollar} in numerous solid state and molecular analogs. Upon protonation, forming H{dollar}sb2{dollar}W{dollar}sb{lcub}10{rcub}{dollar}O{dollar}sbsp{lcub}32{rcub}{lcub}2-{rcub}{dollar}, this activity increases and this has been modeled with atom superposition and electron delocalization molecular orbital (ASED-MO) calculations by shifting the polyoxometalate valence bands by an amount suggested by the observed decrease in first reduction potential. This strengthens the OH bond that forms at the anion surface when an alkane H is abstracted, and lowers the activation energy for the process. The calculations show that in the absence of acid the resulting alkyl radicals bind weakly to the polyanions because the binding is reductive, promoting an electron to the empty W 5d band, but electron transfer to this band is possible for secondary and tertiary carbon radicals over W{dollar}sb{lcub}10{rcub}{dollar}O{dollar}sbsp{lcub}32{rcub}{lcub}4-{rcub}{dollar}, yielding carbocations.; Experiments have shown that the addition of CO to a Rh dimer complex with an acyl ligand causes decarbonylation accompanied by Rh-Rh bond breaking. This is in opposition to known homogeneous reactions. Based on ASED-MO calculations, we find that the driving force for decarbonylation is the stability of the nearly square planar d{dollar}sp8{dollar} Rh that is formed. (Abstract shortened with permission of author.)...