Cleavage, homolytic calculations

The oxidation pathways for alkylated heteroaromatics start with the formation of a radical species, via hydrogen atom loss or alkyl group homolytic bond cleavage. We calculated these BDEs for methyl- and ethyl-substituted derivatives of several key heteroaromatics (Tables 1-3). Few of these experimental values exist therefore. 

AuF is one of the complexes previously calculated using all-electron relativistic MRCI calculations . The Au—F bond length found was 1.946 A and a binding energy of 66.2 kcalmol was calculated for homolytic cleavage these values indicate a shorter and stronger bond than what we calculate at 1.974 A and 60.4 kcalmol, respectively. For AuCr a bond distance of 2.278 A and 58.0 kcalmoP for homolytic cleavage were calculated, and our results are 2.289 A and 59.1 kcalmoP, respectively. 

The S-S bond dissociation energies of H2S2, H2S3 and H2S4 have been studied by Steudel et al. at the GCSD(T)//6-311 G(2df,p) level [42]. The calculated enthalpies AH° for the dissociation at the central bonds at 298 K are 247, 201 and 159 kJ mol respectively. The lower stability of the tri- and tetrasulfanes towards homolytic S-S cleavage is attributed to the stability of the generated HSS radical which is stabilized by the formation of a three-electron n bond. 

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