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Petronilho, Ana
Preferred name
Petronilho, Ana
Official Name
Petronilho, Ana
Research Output
Now showing 1 - 2 of 2
- PublicationIridium Complexes Containing Mesoionic C Donors: Selective C(sp3)-H versus C(sp2)-H Bond Activation, Reactivity Towards Acids and Bases, and Catalytic Oxidation of Silanes and Water(Wiley, 2014-11-24)
; ; ; ; Metalation of a C2-methylated pyridylimidazolium salt with [IrCp*Cl2]2 affords either an ylidic complex, resulting from C(sp3)[BOND]H bond activation of the C2-bound CH3 group if the metalation is performed in the presence of a base, such as AgO2 or Na2CO3, or a mesoionic complex via cyclometalation and thermally induced heterocyclic C(sp2)[BOND]H bond activation, if the reaction is performed in the absence of a base. Similar cyclometalation and complex formation via C(sp2)[BOND]H bond activation is observed when the heterocyclic ligand precursor consists of the analogous pyridyltriazolium salt, that is, when the metal bonding at the C2 position is blocked by a nitrogen rather than a methyl substituent. Despite the strongly mesoionic character of both the imidazolylidene and the triazolylidene, the former reacts rapidly with D+ and undergoes isotope exchange at the heterocyclic C5 position, whereas the triazolylidene ligand is stable and only undergoes H/D exchange under basic conditions, where the imidazolylidene is essentially unreactive. The high stability of the Ir[BOND]C bond in aqueous solution over a broad pH range was exploited in catalytic water oxidation and silane oxidation. The catalytic hydrosilylation of ketones proceeds with turnover frequencies as high as 6 000 h−1 with both the imidazolylidene and the triazolylidene system, whereas water oxidation is enhanced by the stronger donor properties of the imidazol-4-ylidene ligands and is more than three times faster than with the triazolylidene analogue.461Scopus© Citations 47 - PublicationPhotolytic water oxidation catalyzed by a molecular carbene iridium complex(Royal Society of Chemistry, 2012-10-10)
; ; ; ; ; ; ; The complex IrCl2(Cp*)(trz) (trz = triazolylidene), 2, was prepared from readily available 1,3-dimethyl-4-phenyl-1,2,3-triazolium salt. Under basic conditions, the C-bound phenyl group readily cyclometalates, while under acidic conditions, cyclometalation is reversed. The sensitivity of the Caryl–Ir bond but not the Ctrz–Ir bond towards acidolysis provided a basis for using 2 as a catalyst in CeIV-mediated water oxidation. The catalytic activity is characterized by a robust catalytic cycle, affording excellent turnover numbers (TON > 20 000). Under cerium-free conditions and in the presence of hematite as a photoelectrode, light-induced activity was observed. The photoelectrochemical reaction is strongly pH-dependent, which requires pH adjustments when running multiple cycle experiments to regenerate the catalytic activity. Analogous chelating complexes display better stability and higher catalytic activity than the monodentate complex 2.552Scopus© Citations 97