Coordination-Induced Bond Weakening and Electrocatalytic Proton-Coupled Electron Transfer of a Ruthenium Verdazyl Complex
Coordination-Induced Bond Weakening and Electrocatalytic Proton-Coupled Electron Transfer of a Ruthenium Verdazyl Complex
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钌 Verdazyl 配合物的配位诱导键弱化和电催化质子耦合电子转移
DOI：
10.1021/acs.inorgchem.3c02775
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发表时间：
2024
影响因子：
4.6
通讯作者：
Waymouth, Robert M.
中科院分区：
文献类型：
--
作者：
Galvin, Conor M.;Marron, Daniel P.;Dressel, Julia M.;Waymouth, Robert M.
2，4-二异丙基-6-（吡啶-2-基）-1，4-二氢-1，2，4，5-四嗪-3（2 H）-酮VdH与Ru的配位显著削弱了配体的N-H键。电化学测量表明，金属化的无色咪唑钌（VdH）（乙酰丙酮化物）2 RuVdH比自由配体具有更低的pKa（−5单位）、BDFE（−7 kcal/mol）和水合度（−22 kcal/mol）。DFT计算表明，酸度的增加部分归因于共轭碱Vd-的稳定化。当自由时，Vd-扭曲以避免8π e-反芳族态，但当与Ru结合时，它保持平面。质子耦合电子转移（PCET）行为观察到的自由和金属化leucoverdazyls。通过与TEMPOH的PCET平衡，得到了与电化学方法一致的VdHBDFE，RuVdx 2具有电催化PCET给体行为。在酸性条件下，通过RuVdH的1 e-/1H+净转移将持久的三苯甲基自由基·CAr 3（Ar =对叔丁基苯基）还原为相应的三芳基甲烷HCAr 3。
Coordination of the leucoverdazyl ligand 2,4-diisopropyl-6-(pyridin-2-yl)-1,4-dihydro-1,2,4,5-tetrazin-3(2H)-oneVdHto Ru significantly weakens the ligand’s N–H bond. Electrochemical measurements show that the metalated leucoverdazyl Ru(VdH)(acetylacetonate)2RuVdHhas a lower pKa(−5 units), BDFE (−7 kcal/mol), and hydricity (−22 kcal/mol) than the free ligand. DFT calculations suggest that the increased acidity is in part attributable to stabilization of the conjugate baseVd–. When free,Vd–distorts to avoid an 8πe–antiaromatic state, but it remains planar when bound to Ru. Proton-coupled electron transfer (PCET) behavior is observed for both the free and metalated leucoverdazyls. PCET equilibrium between theVdradical and TEMPOH affords aVdHBDFE that is in good agreement with that obtained from electrochemical methods.RuVdexhibits electrocatalytic PCET donor behavior. Under acidic conditions, it reduces the persistent trityl radical ·CAr3(Ar =p-tert-butylphenyl) to the corresponding triarylmethane HCAr3via net 1e–/1H+transfer fromRuVdH.