Theoretical Approaches To Estimating Homolytic Bond Dissociation Energies of Organocopper and Organosilver Compounds

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• 作者：Nicole J. Rijs ; Nigel J. Brookes ; Richard A. J. O鈥橦air ; Brian F. Yates
• 刊名：The Journal of Physical Chemistry A
• 出版年：2012
• 出版时间：September 6, 2012
• 年：2012
• 卷：116
• 期：35
• 页码：8910-8917
• 全文大小：366K
• 年卷期：v.116,no.35(September 6, 2012)
• ISSN：1520-5215

文摘

Although organocopper and organosilver compounds are known to decompose by homolytic pathways among others, surprisingly little is known about their bond dissociation energies (BDEs). In order to address this deficiency, the performance of the DFT functionals BLYP, B3LYP, BP86, TPSSTPSS, BHandHLYP, M06L, M06, M06-2X, B97D, and PBEPBE, along with the double hybrids, mPW2-PLYP, B2-PLYP, and the ab initio methods, MP2 and CCSD(T), have been benchmarked against the thermochemistry for the M鈥揅 homolytic BDEs (D₀) of Cu鈥揅H₃ and Ag鈥揅H₃, derived from guided ion beam experiments and CBS limit calculations (D₀(Cu鈥揅H₃) = 223 kJ路mol^鈥?; D₀(Ag鈥揅H₃) = 169 kJ路mol^鈥?). Of the tested methods, in terms of chemical accuracy, error margin, and computational expense, M06 and BLYP were found to perform best for homolytic dissociation of methylcopper and methylsilver, compared with the CBS limit gold standard. Thus the M06 functional was used to evaluate the M鈥揅 homolytic bond dissociation energies of Cu鈥揜 and Ag鈥揜, R = Et, Pr, iPr, tBu, allyl, CH₂Ph, and Ph. It was found that D₀(Ag鈥揜) was always lower (50 kJ路mol^鈥?) than that of D₀(Cu鈥揜). The trends in BDE when changing the R ligand reflected the H鈥揜 bond energy trends for the alkyl ligands, while for R = allyl, CH₂Ph, and Ph, some differences in bond energy trends arose. These trends in homolytic bond dissociation energy help rationalize the previously reported (Rijs, N. J.; O鈥橦air, R. A. J. Organometallics2010, 29, 2282鈥?291) fragmentation pathways of the organometallate anions, [CH₃MR]^鈭?/sup>.