The Ferraquinone–Ferrahydroquinone Couple: Combining Quinonic and Metal-Based Reactivity

Abstract

A ferraquinone–ferrahydroquinone organometallic redox couple was prepared and characterized. Intricate cooperativity of the metal was observed with different positions on the ligand. This allowed cooperative activation of small molecules like molecular hydrogen, oxygen, and bromine. Likewise, dehydrogenation of alcohols was achieved through 1,6 metal–ligand cooperation.

Natural inspirations for metal–ligand cooperative catalysis

“…The biomimetic chemistry of hydrogenases is now well established, and readers wishing to learn more about these themes are directed to several useful reviews 6,8,9,52, [55][56][57][58] . 'ferrahydroquinone' 6H 2 is generated in either case 40 . Although the ligands present in 6 are quite different from those bound to Ni in lactate racemase, the direct involvement of the pincer ligand bears resemblance to the native mechanism.…”

“…D | Density functional theory computations for catalyst 5 predict that it performs alcohol dehydrogenation by means of metal-ligand cooperativity, with the pincer ligand accepting H − at either the 4 position (pictured) or the 2 position39 . E | The Fe 0 ferraquinone 6 can activate H 2 and dehydrogenate primary alcohols to aldehydes, thereby affording ferrahydroquinone 6H 2 (REF 40…”

Regioselective Gas‐Phase n‐Butane Transfer Dehydrogenation via Silica‐Supported Pincer‐Iridium Complexes

“…These fractions were then combined and dried over sodium sulfate, filtered again and the solvent was removed in vacuo to yield a viscous yellow oil (1.72 g, 1.11×10 −2 mol, 46.6 % yield). Identity of the product was confirmed by comparison to reported NMR spectra [11b] …”

“…The final product (1.82 g, 46 %) was isolated via column chromatography using a 3 : 1 hexanes:diethyl ether solvent. Identity of the product was confirmed by comparison to reported NMR spectra [11b] …”

Dearomatization of the PCP Pincer Ligand in a ReV Oxo Complex

“…Milstein and co-workers previously exploredd earomatization of modified PCPl igandsb yd eprotonation of a para-hydroxy group (Scheme1), [7,8] but "dearomatization" of PCP ligands by loss of ap rotonf rom ab enzylic CH 2 positionh as not been reportedt od ate. This absence is noteworthy given the prominenceo fP CP in organometallic explorations of bond breaking.…”