Ethyl-2-pyridyl)porphyrin (complex and 8.six for the isomeric N-methyl-4-pyridyl (4TMPy

Cp2Fe+/0) however is in a position to abstract H?from relatively strong phenolic O-H bonds.402 According to these benefits and eq 7, they concluded that the reduced MnIVO species should be fairly standard. Related ruthenium compounds with porphyrin, salen or tetramine macrocycles have also per.1944 been studied in detail, as has been reviewed elsewhere.403 As an example, Lau and coworkers have studied in detail oxidation reactions of trans-[RuVI(tmc)(O)2]2+, trans-[RuIV(tmc)(O) (solv)]2+, and trans-[RuII(tmc)(H2O)2]2+, exactly where tmc will be the macrocyclic tertiary amine ligand 1,4,eight,11-tetramethyl-1,4,eight,11-tetraazacyclotetradecane.404 A full Pourbaix diagram was created from aqueous electrochemical information, which indicates BDFEs of 74.3 kcal mol-NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author ManuscriptChem Rev. Author manuscript; out there in PMC 2011 December 8.Warren et al.Pagefor RuV(O)(O ) and 82.5 kcal mol-1 for RuIV(O)(HO ).405 Consistent with these values, this and related complexes abstract H?from alkylaromatic compounds.406 Lau et al. have also shown that Lewis acids can tremendously enhance the capability of oxo reagents to abstract H?from C bonds, on account of the stabilization in the lowered oxidant by the Lewis acid and therefore the larger O BDFE within the presence in the acid.407 The very first studies of metal-mediated HAT in our labs Xidation of guanine occurs with loss with the N1 proton (Scheme involved chromyl chloride (CrO2Cl2) and permanganate.211,408,409 The identified aqueous E?MnO42-/-) = 0.564 V and pKa(HMnO4-) = 7.four give, employing equation 7, BDFE(O3MnO -) = 80.7 kcal mol-1 (which was reported originally as a BDE of 80 ?3 kcal mol-1). The capacity of CrO2Cl2 and MnO4- to abstract H?from hydrocarbons was rationalized around the basis of this bond strength, which can be high for isolable, stable species. Much more recently, H-transfer reactions of cis-vanadium dioxo complexes, (bpy)2VV(O)2+, have been examined,24 in addition to a VO BDFE of 70.6 kcal mol-1 was obtained by equilibration with 2,6-di-tert-butyl-4-methoxyphenol. This program has unusually large barriers to HAT which are pnas.1408988111 as a result of the substantial inner-sphere reorganization that occurs in between (bpy)2VV(O)2+ and (bpy)2VIV(O)(OH)+.24 Bridging oxo and hydroxo ligands can also be involved in PCET reactions. Pecoraro, Baldwin, and Caudle,410,411 and independently Brudvig, Crabtree and Thorp,412 showed that dimeric -oxo manganese compounds for example [(phen)2MnIV(-O)2MnIII(phen)2]3+ ([MnIVMnIII2(O)2]3+, phen = 1,10-phenanthroline) are reduced with addition of protons to produce [MnIII2(O)(OH)]3+ and [MnIIIMnII(OH)2]3+.Ethyl-2-pyridyl)porphyrin (complex and 8.6 for the isomeric N-methyl-4-pyridyl (4TMPy) derivative.399 They have also estimated, employing price constants for HAT reactions plus the Br sted-Evans-Polanyi partnership, O bond dissociation enthalpies of one hundred kcal mol-1 for [(5,ten,15,20-tetra(N-methyl-4'pyridylporphyrin))FeIVOH]5+, 92 kcal mol-1 for [(5,ten,15,20tetra(mesityl)porphyrin)FeIVOH]+, and 86 kcal mol-1 for [(5,10,15,20tetra(pentafluorophenyl)]porphyrin)FeIVOH]+.400 Shaik et al.