Crystal structure of a side-on superoxo complex of cobalt and hydrogen abstraction by a reactive terminal oxo ligand

Egan, James W.; Haggerty, Brian S.; Rheingold, Arnold L.; Sendlinger, Shawn C.; Theopold, Klaus

doi:10.1021/ja00162a069

Cited by 163 publications

(126 citation statements)

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“…In all other respects, the low and high T structures are identical; the average CoON distance is identical in both, and the average CoOO is 1.81 Å at 22°C and 1.83 Å at Ϫ123°C. Collection of data at high T on the same crystal used for the low T structure reproduced the structural parameters reported in 1990 (11). Thus, we can conclude that, whereas there are generally only minor and usually chemically insignificant differences in bond parameters as a function of the temperature of data collection, in this case, the difference in the OOO distance is extraordinarily large and reproducible.…”

supporting

confidence: 66%

“…A Bruker/Nonius (Billerica, MA) platform goniometer with an APEX charge-coupled device detector and a Kryo-Flex low-temperature unit was used to collect data. The structure was processed with the parameters from the earlier room-temperature determination (11). All nonhydrogen atoms were refined with anisotropic thermal parameters and hydrogen atoms were treated as idealized contributions.…”

Section: Methodsmentioning

confidence: 99%

“…For example, whereas 1 and 2 (as reported in ref. 11, denoted ''high T''; see below) show similarly short OOO distances in their x-ray structures, the measured OO for 1 is 151 cm Ϫ1 higher than that measured for 2 (high T). The OOO distance in 4 is 0.065 Å greater than in 2 (high T), yet the OO for 4 is higher by 111 cm…”

mentioning

confidence: 87%

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Variable character of O—O and M—O bonding in side-on (η ² ) 1:1 metal complexes of O ₂

Cramer

Tolman

Theopold

et al. 2003

Proc. Natl. Acad. Sci. U.S.A.

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334

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The structures and the OOO and MOO bonding characters of a series of reported side-on ( 2 ) 1:1 metal complexes of O2 are analyzed by using density functional theory calculations. Comparison of the calculated and experimental systems with respect to OOO bond distance, OOO stretching frequency, and OOO and MOO bond orders provides new insights into subtle influences relevant to O2 activation processes in biology and catalysis. The degree of charge transfer from the generally electronrich metals to the dioxygen fragment is found to be variable, such that there are species well described as superoxides, others well described as peroxides, and several cases having intermediate character. Increased charge transfer to dioxygen takes place via overlap of the metal dxy orbital with the in-plane * orbital of O2 and results in increased MOO bond orders and decreased OOO bond orders. Comparison of theory and experiment over the full range of compounds studied suggests that reevaluation of the OOO bond lengths determined from certain x-ray crystal structures is warranted; in one instance, an x-ray crystal structure redetermination was performed at low temperature, confirming the theoretical prediction. Librational motion of the coordinated O2 is identified as a basis for significant underestimation of the OOO distance at high temperature. With the longstanding goal of understanding in detail how dioxygen binds and is activated at metal centers in biological and catalytic systems, great effort has been expended to characterize the structures, physicochemical properties, and reactivity of metal-dioxygen complexes (1-8). As the initially formed species in most oxidation processes, 1:1 metal-O 2 adducts are of special interest, particularly in view of their postulated involvement in enzymes that react with dioxygen at an isolated monometallic active site, such as Cu in dopamine ␤-monooxygenase or galactose oxidase (9). Two binding modes have been identified in 1:1 metal-O 2 complexes, end-on ( 1 ) and side-on ( 2 ). These adducts have been further defined as superoxo or peroxo complexes, primarily on the basis of x-ray structural data (OOO bond distance) and vibrational spectroscopy (OOO stretching frequency, OO ) (1-4). Thus, compounds with an OOO bond length of Ϸ1.4-1.5 Å and OO between Ϸ800 and 930 cm Ϫ1 are designated as peroxides, whereas those with OOO Ϸ1.2-1.3 Å and OO Ϸ1,050-1,200 cm Ϫ1 fall into the superoxide category. On this basis, and keeping in mind the caveat that it is often difficult to assess experimentally the actual amount of charge transferred to dioxygen on complexation, the majority of the known 2 1:1 compounds are generally agreed to be best described as peroxo complexes (1,5,8).Reports of , Tris(3,5-dimethylpyrazol-1-yl)hydroborate) (13) (Scheme 1). In the course of the investigation of 6, for which intermediate character of the dioxygen unit was found (14, 15), we noted puzzling incongruities among the data reported for these complexes (Table 1). For example, whereas 1 and 2 (as reported in ref. 11, d...

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supporting

confidence: 66%

Section: Methodsmentioning

confidence: 99%

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Variable character of O—O and M—O bonding in side-on (η ² ) 1:1 metal complexes of O ₂

Cramer

Tolman

Theopold

et al. 2003

Proc. Natl. Acad. Sci. U.S.A.

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334

319

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“…[5] Among other factors, the nature of the transition metals in M-O 2 C À species is also important, as it determines the electronic structure and the reactivity of these species. Over the years, the synthesis, structure, and reactivity of superoxo species containing copper, [6] iron, [5,7] and manganese [8] have been reported along with other metals.[9] An important addition to this class is the report of the crystal structure of the end-on Cr-O 2 C À species and kinetic studies to probe its ability to perform C À H bond activation in hydrocarbons. [10] Metal-superoxo species are generally transient in nature and are generated at the first step of the oxygen activation both in enzyme catalysis and in biomimetic chemistry.…”

mentioning

confidence: 99%

CH Bond Activation by Metal–Superoxo Species: What Drives High Reactivity?

Ansari¹,

Jayapal²,

Rajaraman³

2014

Angewandte Chemie

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Metal-superoxo species are ubiquitous in metalloenzymes and bioinorganic chemistry and are known for their high reactivity and their ability to activate inert CÀH bonds. The comparative oxidative abilities of M-O 2 C À species (M = Cr III , Mn III , Fe III , and Cu II ) towards CÀH bond activation reaction are presented. These superoxo species generated by oxygen activation are found to be aggressive oxidants compared to their high-valent metal-oxo counterparts generated by O···O bond cleavage. Our calculations illustrate the superior oxidative abilities of Fe III -and Mn III -superoxo species compared to the others and suggest that the reactivity may be correlated to the magnetic exchange parameter.Mononuclear metalloenzymes with coordinated oxygen at the metal center have applications in biology, industry, and the laboratory.[1] Oxygenated metal intermediates like oxo, peroxo, hydroperoxo, and superoxo species play a vital role in catalytic reactions such as hydrogenation, halogenation, hydroxylation, olefin epoxidation, and C À H bond activation.[2] In the last decade many high-valent metal-oxygen species have been studied to understand the fundamental structural, functional, and mechanistic aspects of their enzymes and their counterparts. [2a,d, 3] Apart from the metaloxo species, oxidation of CÀH bonds by several superoxometal complexes is also reported.[4] Unlike the metal-oxo species, the reactivity of M-O 2 C À species and their competing oxidative abilities are relatively less explored, although nature utilizes both species to carry out efficient catalysis. [5] Among other factors, the nature of the transition metals in M-O 2 C À species is also important, as it determines the electronic structure and the reactivity of these species. Over the years, the synthesis, structure, and reactivity of superoxo species containing copper, [6] iron, [5,7] and manganese [8] have been reported along with other metals.[9] An important addition to this class is the report of the crystal structure of the end-on Cr-O 2 C À species and kinetic studies to probe its ability to perform C À H bond activation in hydrocarbons. [10] Metal-superoxo species are generally transient in nature and are generated at the first step of the oxygen activation both in enzyme catalysis and in biomimetic chemistry. [7c, 10b] As these species are key intermediates in iron and copper catalysis, it suggests that the M-O 2 C À species perhaps play a larger role as an oxidant in enzyme catalysis. [6,11] In the M-O 2 C À species the unpaired electrons on the metal and the radical center are strongly coupled and the electronic configuration of the metal ions dictates the nature of the magnetic coupling (J) and this may in turn correlate to the CÀH bond activation. Here we have undertaken a detailed theoretical study to specifically address the following questions 1) probing the mechanism of C À H bond activation by Cr-O 2 C À and its comparative oxidative ability to high-valent metal-oxo species, 2) establishing the comparative oxidativ...

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“…Terminale Co IV -O-Komplexe wurden als reaktive Intermediate bei Cobalt-vermittelten Alkanhydroxylierungen [1] und der katalytischen Vierelektronenreduktion von Disauerstoff zu Wasser [2] vorgeschlagen. Ein direkter spektroskopischer Nachweis von Co IV -Spezies in diesen Systemen stand bisher jedoch aus, sodass eine definitive Zuordnung ungewiss war.…”

Section: Professor Karl Wieghardt Zur Emeritierung Gewidmetunclassified

Ein Cobalt(IV)‐Oxido‐Komplex: Stabilisierung durch Lewis‐Säure‐Wechselwirkung mit Sc³⁺

et al. 2010

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Seltene Spezies: Ein schwer fassbarer Oxocobalt(IV)‐Komplex mit S=3/2 wurde mithilfe einer Lewis‐Säure‐Wechselwirkung mit einem Sc3+‐Ion stabilisiert. Die CoIV‐O‐Sc3+‐Einheit, die durch verschiedene spektroskopische und DFT‐Methoden charakterisiert wurde, zeigt stärkeres Elektronentransfer‐ und H‐Abstraktionsvermögen, dafür aber langsameren Oxo‐Transfer als der entsprechende FeIVO‐Komplex (siehe Schema; L=Tris[2‐(N‐tetramethylguanidyl)ethyl]amin).

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Crystal structure of a side-on superoxo complex of cobalt and hydrogen abstraction by a reactive terminal oxo ligand

Cited by 163 publications

References 1 publication

Variable character of O—O and M—O bonding in side-on (η ² ) 1:1 metal complexes of O ₂

Variable character of O—O and M—O bonding in side-on (η ² ) 1:1 metal complexes of O ₂

CH Bond Activation by Metal–Superoxo Species: What Drives High Reactivity?

Ein Cobalt(IV)‐Oxido‐Komplex: Stabilisierung durch Lewis‐Säure‐Wechselwirkung mit Sc³⁺

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Crystal structure of a side-on superoxo complex of cobalt and hydrogen abstraction by a reactive terminal oxo ligand

Cited by 163 publications

References 1 publication

Variable character of O—O and M—O bonding in side-on (η 2 ) 1:1 metal complexes of O 2

Variable character of O—O and M—O bonding in side-on (η 2 ) 1:1 metal complexes of O 2

CH Bond Activation by Metal–Superoxo Species: What Drives High Reactivity?

Ein Cobalt(IV)‐Oxido‐Komplex: Stabilisierung durch Lewis‐Säure‐Wechselwirkung mit Sc3+

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Variable character of O—O and M—O bonding in side-on (η ² ) 1:1 metal complexes of O ₂

Variable character of O—O and M—O bonding in side-on (η ² ) 1:1 metal complexes of O ₂

Ein Cobalt(IV)‐Oxido‐Komplex: Stabilisierung durch Lewis‐Säure‐Wechselwirkung mit Sc³⁺