H₂O‐Aktivierung für den Wasserstoffatom‐Transfer: korrekte Strukturen, revidierte Mechanismen

Hydrogen Generation by Water Reduction with [Cp*2Ti(OTf)]: Identifying Elemental Mechanistic Steps by Combined In Situ FTIR and In Situ EPR Spectroscopy Supported by DFT Calculations

“…Furthermore, we tested the stabilizing effect of H 2 O and THF as solvent through hydrogen bonding to the coordinated H 2 O molecules (Scheme 6). Stabilization of water ligands in titanocene complexes by hydrogen bonds from THF was found by Gansäuer et al [7] However, the positive free ener- This might be due to the fact that the a-hydrogen of THF points to the methyl group of the pentamethylcyclopentadienyl ligand. Based on these results, a direct participation of THF in these reactions can be excluded.…”

“…been recently detected upon reaction of Zn-reduced [Cp 2 Ti III Cl 2 ] with water; however, a large excess of water was necessary. [7] However, unequivocal evidence for the exact nature of 3, for example, from X-ray single-crystal analysis is still missing. Moreover, some important issues of the reaction mechanism are still unclear, including the nature of complex 3 in solution, the likely presence of other intermediates in solution, as well as the question of molecular hydrogen formation from only one H atom per reaction cycle.…”

Cp2TiX Complexes for Sustainable Catalysis in Single‐Electron Steps

“…For Cp 2 TiOTf ap eak potentialo fÀ0.31 Vw as measured on the oxidative sweep ( Figure 1, turquoise voltammogram) that is generally associated with the generation of Cp 2 Ti + . [12,13,20] Therefore, OTf À can dissociate from Ti even in THF without the aid of aL ewis acid. It is noteworthy,t hat the cationic species Cp 2 Ti + is not generated during the sweep by as oc alled parent-child reactionb ecause the oxidationc urrent of Cp 2 Ti + does not decreases ignificantly upon increasingt he sweep rate, which is otherwise indicativef or this reaction.…”

Activation of O−H and C−O Bonds in Water and Methanol by a Vanadium‐Bound Thiyl Radical

“…[12] Recently,i tw as also found that OÀHb ond can be weakened via water coordinationt oaMo complex, then activated with the evolution of H 2 . [13] H 2 Oi sw eakeneda nd activated by coordinationt oatitanium center or through the second coordination sphere interactioni n[ Cp 2 TiCl], [14] thus serving as ah ydrogen-atomt ransfer reagent. [15] In this work, we demonstrate that an isolated vanadium-bound thiyl radicals peciesh as the reactivity to activate H 2 Oa nd CH 3 OH through the cleavage of strong OÀHa nd CÀO bonds.…”