Remote Multiproton Storage within a Pyrrolide‐Pincer‐Type Ligand

Abstract

A chemically non-innocent pyrrole-based trianionic (ONO)(3-) pincer ligand within [(pyr-ONO)TiCl(thf)2 ] (2) can access the dianionic [(3H-pyr-ONO)TiCl2 (thf)] (1-THF) and monoanionic [(3H,4H-pyr-ONO)TiCl2 (OEt2 )][B{3,5-(CF3 )2 C6 H3 }4 ] (3-Et2 O) states through remote protonation of the pyrrole γ-C π-bonds. The homoleptic [(3H-pyr-ONO)2 Zr] (4) was synthesized and characterized by X-ray diffraction and NMR spectroscopy in solution. The protonation of 4 by [H(OEt2 )2 ][B{C6 H3 (CF3 )2 }4 ] yields [(3H,4H-pyr-ONO)(3H-pyr-ONO)Zr][B{3,5-(CF3 )2 C6 H3 }4 ] (5), thus demonstrating the storage of three protons.

Catalytic transformation of dinitrogen into ammonia and hydrazine by iron-dinitrogen complexes bearing pincer ligand

“…The blue-shift of II is consistent with the observed shift (+70 cm −1 ) shown in Fig. 6 , which can be ascribed to the protonation of the pyrrole ring of the PNP ligand 49 . All the results indicate that the protonation of 1 is not suitable for the formation of N–H bond of the coordinated N 2 ligand.…”

“…The result reveals that the first protonation at 1 may occur not at the coordinated dinitrogen ligand but at the pyrrole moiety in 1 (ref. 49 ). When we attempted to reduce 5 with 1 equiv of KC 8 as a reductant in Et 2 O at room temperature for 10 min, a mixture of 1 and free PNP-H was observed in 38 and 27% yields by 1 H NMR, respectively, together with the formation of 3 in 3% yield.…”

Radical‐Type Reactivity and Catalysis by Single‐Electron Transfer to or from Redox‐Active Ligands

“…[57] However,s trategies to effectively bridge redox non-innocence and such chemical non-innocence have been only scarcely identified to date. [58][59][60][61][62] However,i ft his selective ligand-centered hydrogen-based chemistry could be exploited alongside the established electron-based reactivity of such ligands, this might allow for interesting crossover studies between previously disparate ligand-based reactivity patterns. Ultimately,t his offers the foresight of selective and efficient proton-coupled electron transfer [63] in catalysis.I ti st herefore deemed only am atter of Scheme10.…”

Iron pyrrole-based PNP pincer ligand complexes as catalyst precursors

“…This complex is anticipated to either act as a catalyst or serve as a precursor to new first-row transition-metal-based catalysts after substitution or loss of a ligand. However, attempts to hydrogenate the pyrrole backbone, as was observed by Nadif et al (2015) and Kuriyama et al (2016), or to displace one of the coordinating ligands with a hydride without the use of a hydride donor were unsuccessful. The diamagnetic complex (I) was characterized by 1 H and 31 P NMR spectroscopy.…”