Metalloradical Compounds with 1,2-Dipivaloylhydrazido Ligands: Electron Transfer and Alkylation/Protonation Effects

0505695 - ÚFCH JH 2020 RIV DE eng J - Článek v odborném periodiku
Mondal, S. - Filippou, V. - Bubrin, M. - Schwederski, B. - Fiedler, Jan - Kaim, W.
Metalloradical Compounds with 1,2-Dipivaloylhydrazido Ligands: Electron Transfer and Alkylation/Protonation Effects.
European Journal of Inorganic Chemistry. Roč. 2019, č. 21 (2019), s. 2639-2647. ISSN 1434-1948. E-ISSN 1099-0682
Grant CEP: GA ČR(CZ) GA18-09848S
Institucionální podpora: RVO:61388955
Klíčová slova: EPR spectroscopy * Hydrazine * Ruthenium * Spectroelectrochemistry * Spin density
Obor OECD: Physical chemistry
Impakt faktor: 2.529, rok: 2019
Způsob publikování: Omezený přístup

Under oxidative conditions the complexes M(bpy)2Cl2, M = Ru or Os, react with 1,2-dipivaloylhydrazine H2L = tBuC(O)-NH-NH-C(O)-tBu to yield the paramagnetic compounds [M(L)(bpy)2](PF6) {1(PF6), M = Ru and 2(PF6), M = Os}. Crystal structures of 1(ClO4) and 2(PF6) reveal an NNCO chelate coordination of L with d(NN) ≈ 1.39 Å. EPR spectroscopy suggests a metal/ligand mixed situation for the unpaired electron, with 29 % (Ru, 1+) or 46 % (Os, 2+) metal spin contribution according to DFT calculations. Both complex cations exhibit reversible one-electron oxidation and reduction (Kc ≈ 1019 for 1+ and 1012 for 2+) which could also be monitored by IR (νCO) and UV/Vis-NIR spectroelectrochemistry. These data confirm a metal/ligand orbital mixing MII(L·–) ↔ MIII(L2–), with the osmium analogue favoring the latter alternative. Reaction of Ru(bpy)2Cl2 under non-oxidizing conditions yields the intermediate (1H)(PF6) which could be oxidatively deprotonated to 1+ or methylated to (1Me)(PF6), both identified by 1H and 13C NMR. While oxidation of (1H)+ proceeds irreversibly due to proton loss, the reversible spectroelectrochemical oxidation of (1Me)+ suggests a metal-based process RuII(LMe–) → RuIII(LMe–). The results reveal that not only dinuclear complexes of 1,2-diacylhydrazido ligands but also mononuclear analogues are distinguished by remarkably variable metal/ligand mixed contributions to the frontier orbitals.
Trvalý link: http://hdl.handle.net/11104/0297107