Comparing Metal–Halide and −Oxygen Adducts in Oxidative C/O–H Activation: Au^III–Cl versus Au^III–OH

Abstract

High-valent metal–halides have come to prominence as highly effective oxidants. A direct comparison of their efficacy against that of traditional metal–oxygen adducts is needed. [Au III (Cl)(terpy)](ClO 4 ) 2 ( 1 ; terpy = 2,2′:6′,2-terpyridine) readily oxidized substrates bearing O–H and C–H bonds via a hydrogen atom transfer mechanism. A direct comparison with [Au III (OH)(terpy)](ClO 4 ) 2 ( 2 ) showed that 1 was a kinetically superior oxidant with respect to 2 for all substrates tested. We ascribe this to the greater thermodynamic driving force imbued by the Cl ligand versus the OH ligand.

Homolytic X‐H Bond Cleavage at a Gold(III) Hydroxide: Insights into One‐Electron Events at Gold

“…The complex [Au(OH)(terpy)](ClO 4 ) 2 , where terpy is 2,2’ : 6’,2‐terpyridine, is capable of performing PCET reactions with 1,4‐cyclohexadiene (CHD), 9,10‐dihydroanthracene (DHA), and a variety of electron rich phenols [3,6] . These reactions were proposed to proceed via HAT based on kinetic data [3] .…”

“…The complex [Au(OH)(terpy)](ClO 4 ) 2 , where terpy is 2,2' : 6',2terpyridine, is capable of performing PCET reactions with 1,4cyclohexadiene (CHD), 9,10-dihydroanthracene (DHA), and a variety of electron rich phenols. [3,6] These reactions were proposed to proceed via HAT based on kinetic data. [3] We note that the isoelectronic Cu(III)-hydroxide complex, (N^N^N)Cu-(OH) where (N^N^N) is N,N'-bis(2,6-diisopropylphenyl)-2,6-pyridinedicarboxamide, has similarly been shown to perform PCET with DHA and phenols.…”

Oxidative versus basic asynchronous hydrogen atom transfer reactions of Mn(iii)-hydroxo and Mn(iii)-aqua complexes

“…Mechanisms of hydrogen atom transfer (HAT) reactions from organic substrates (SH) to metal-oxygen complexes, such as metal-oxo, metal-hydroxo, [24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39] metal-(hydro)peroxo [40][41][42][43][44] and metal-superoxo, [45][46][47][48][49][50][51][52][53][54] have been investigated extensively, as summarized in Scheme 1. HAT proceeds via the transfer of both a proton and an electron which can be transferred simul-spectrum of "asynchronicity", in which the transition state for the HAT reaction can contain either more PT or more ET character (Scheme 1).…”

“…Mechanisms of hydrogen atom transfer (HAT) reactions from organic substrates (SH) to metal–oxygen complexes, such as metal-oxo, 1–23 metal-hydroxo, 24–39 metal-(hydro)peroxo 40–44 and metal-superoxo, 45–54 have been investigated extensively, as summarized in Scheme 1. HAT proceeds via the transfer of both a proton and an electron which can be transferred simultaneously in a coupled fashion (concerted proton–electron transfer, CPET) or a stepwise fashion (proton transfer–electron transfer, PT/ET, or electron transfer–proton transfer, ET/PT) (Scheme 1).…”

Deprotonation from an OH on myo-Inositol Promoted by μ2-Bridges with Possible Regioselectivity/Chiral Selectivity

“…Proton transfer is one of the most fascinating fundamental phenomena as it is involved in a variety of reactions in biological synthesis and industrial manufacture. For example, proton transfer plays key roles in photosynthesis, respiration, and enzymatic catalysis. , In many cases, chemically relatively inert groups such as N–H and O–H are activated by metal ions so that deprotonations occur in these groups. − The relevant deprotonation may trigger a cascade of chemical conversions. Up to now, however, the extent of understanding of the physicochemical basis of the proton transfer promoted by metal ions is still rather limited.…”