Bis(sulfonylimide)ruthenium(VI) Porphyrins: X‐ray Crystal Structure and Mechanism of CH Bond Amination by Density Functional Theory Calculations

Guo, Zhen; Guan, Xiangguo; Huang, Jie; Tsui, Wai-Man; Lin, Zhenyang; Ming, Chi

doi:10.1002/chem.201300021

Cited by 41 publications

(37 citation statements)

References 158 publications

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“…8 These two [Ru VI (por)(NY) 2 ] complexes show similar orientation of the axial arylimide ligands with respect to the corresponding porphyrin ring. Their RuN(imide) distances are comparable to, and the axial imide ligands are more bent than, those of the sulfonylimide analogue [Ru VI (tmp)(NSO 2 {Ar‐ p ‐OMe}) 2 ] (RuN(imide) 1.79(3) Å, axial Ru‐N‐S: 162.5(3)°) 36…”

Section: Resultsmentioning

confidence: 98%

Ruthenium Porphyrins with Axial π‐Conjugated Arylamide and Arylimide Ligands

Law

Chen

Chan

et al. 2014

Chemistry A European J

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A series of ruthenium porphyrins [Ru(IV)(por)(NHY)2] and [Ru(VI)(por)(NY)2] bearing axially coordinated π-conjugated arylamide and arylimide ligands, respectively, have been synthesized. The crystal structures of [Ru(IV)(tmp)(NHY)2] (tmp = 5,10,15,20-tetramesitylporphyrinato(2-)) with Y = 4'-methoxy-biphenyl-4-yl (Ar-Ar-p-OMe), 4'-chloro-biphenyl-4-yl (Ar-Ar-p-Cl), and 9,9-dibutyl-fluoren-2-yl (Ar^Ar) show axial Ru-N(arylamide) distances of 1.978(4), 1.971(6), and 1.985(13) Å, respectively. [Ru(IV)(tmp)(NH{Ar^Ar})2] is an example of metalloporphyrins that bind an arylamide ligand featuring a co-planar biphenyl unit. The [Ru(IV)(por)(NHY)2] complexes show a quasi-reversible reduction couple or irreversible reduction wave attributed to Ru(IV)→Ru(III) with Epc from -1.06 to -1.40 V versus Cp2Fe(+/0) and an irreversible oxidation wave with Epa from -0.04 to 0.19 V versus Cp2Fe(+/0). Reaction of the [Ru(IV)(por)(NHY)2] with bromine afforded [Ru(IV)(por)(NHY)Br]. PhI(OAc)2 oxidation of the [Ru(IV)(por)(NHY)2] gave [Ru(VI)(por)(NY)2]; the latter can be prepared from reaction of [Ru(II)(por)(CO)] with aryl azides N3Y. The crystal structure of [Ru(VI)(tmp)(N{Ar-Ar-p-OMe})2] features Ru-N(arylimide) distances of 1.824(5) and 1.829(5) Å. Alkene aziridination and C-H amination catalyzed by "[Ru(II)(tmp)(CO)]+π-conjugated aryl azides", or mediated by [Ru(VI)(por)(NY)2] with Y = biphenyl-4-yl (Ar-Ar) and Ar-Ar-p-Cl, gave aziridines and amines in moderate yields. The electronic structure of [Ru(VI)(por)(NY)2] was examined by DFT calculations.

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Section: Resultsmentioning

confidence: 98%

Ruthenium Porphyrins with Axial π‐Conjugated Arylamide and Arylimide Ligands

Law

Chen

Chan

et al. 2014

Chemistry A European J

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“…40 Whereas carbenes are generally too reactive for characterization, some of these metallocarbenoid species proved to be stable enough for isolation and X-ray crystallography analysis. 41 These isolated metallocarbenoids participate in cyclopropanation reactions, providing evidence that metalloporphyrin-catalyzed cyclopropanations proceed through the metallocarbenoid intermediates.…”

Section: Using Mechanistic Similarities and Directed Evolution To mentioning

confidence: 99%

Expanding the Enzyme Universe: Accessing Non‐Natural Reactions by Mechanism‐Guided Directed Evolution

2015

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High selectivities and exquisite control over reaction outcomes entice chemists to use biocatalysts in organic synthesis. However, many useful reactions are not accessible because they are not in nature’s known repertoire. We will use this review to outline an evolutionary approach to engineering enzymes to catalyze reactions not found in nature. We begin with examples of how nature has discovered new catalytic functions and how such evolutionary progressions have been recapitulated in the laboratory starting from extant enzymes. We then examine non-native enzyme activities that have been discovered and exploited for chemical synthesis, emphasizing reactions that do not have natural counterparts. The new functions have mechanistic parallels to the native reaction mechanisms that often manifest as catalytic promiscuity and the ability to convert from one function to the other with minimal mutation. We present examples of how non-natural activities have been improved by directed evolution, mimicking the process used by nature to create new catalysts. Examples of new enzyme functions include epoxide opening reactions with non-natural nucleophiles catalyzed by a laboratory-evolved halohydrin dehalogenase, cyclopropanation and other carbene transfer reactions catalyzed by cytochrome P450 variants, and non-natural modes of cyclization by a modified terpene synthase. Lastly, we describe discoveries of non-native catalytic functions that may provide future opportunities for expanding the enzyme universe.

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“…Further support for the proposed mechanism has been obtained using densityfunctional theory 38 , while isolable complexes of the type A and D have been structurally characterised. 19,39 In this article, we will explore the potential of resonance Raman spectroscopy as a tool to investigate the proposed mechanistic steps for the homogeneously-catalysed reaction shown in Figure 1 at different cyclohexene concentrations. It is envisaged that monitoring the timedependent shifts in the vibrational modes of the porphyrin skeleton present in the various ruthenium-porphyrin complexes will shed further light on the identity for the intermediate states of the catalyst.…”

Section: Introductionmentioning

confidence: 99%

Resonance Raman spectroscopy as an in situ probe for monitoring catalytic events in a Ru–porphyrin mediated amination reaction

Zardi

Gallo

Solan

et al. 2016

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ABSTRACT:Resonance Raman microspectroscopy has been widely used to study the structure and dynamics of porphyrins and metal complexes containing the porphyrin ligand. Here, we have demonstrated that the same technique can be adapted to examine the mechanism of a homogeneously-catalysed reaction mediated by a transition-metal-porphyrin complex.Previously it has been challenging to study this type of reaction using in situ spectroscopic monitoring due to the low stability of the reaction intermediates and elevated-temperature conditions. We have made a straightforward modification to the sample stage on a microscope for time-lapsed Raman microspectroscopy from reaction mixtures in these media. The allylic amination of unsaturated hydrocarbons by aryl azides, which can be catalysed by a rutheniumporphyrin complex, has been used as an illustrative example of the methodology. The mechanism of this particular reaction has been studied previously using density-functional theory and kinetic approaches. The Raman measurements support the mechanism proposed in the earlier publications by providing the first experimental verification of a precursor reaction complex between the aryl azide and the ruthenium metal ion, and evidence for the formation of a mono-imido intermediate complex under conditions of high concentration of the reactant olefin.

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Bis(sulfonylimide)ruthenium(VI) Porphyrins: X‐ray Crystal Structure and Mechanism of CH Bond Amination by Density Functional Theory Calculations

Cited by 41 publications

References 158 publications

Ruthenium Porphyrins with Axial π‐Conjugated Arylamide and Arylimide Ligands

Ruthenium Porphyrins with Axial π‐Conjugated Arylamide and Arylimide Ligands

Expanding the Enzyme Universe: Accessing Non‐Natural Reactions by Mechanism‐Guided Directed Evolution

Resonance Raman spectroscopy as an in situ probe for monitoring catalytic events in a Ru–porphyrin mediated amination reaction

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