Beyond Heme‐Thiolate Interactions: Roles of the Secondary Coordination Sphere in Cytochrome P450 Systems

Lu, Yi; Pfister, Thomas D.

doi:10.1002/9780470028155.ch9

Cited by 3 publications

(2 citation statements)

References 63 publications

(103 reference statements)

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“…Part of this discrepancy is due to a redox mismatch between O 2 and Ni(II): most known Ni–O 2 adducts require prior reduction to the Ni(I) state − or the use of already reduced O 2 units (H 2 O 2 and base). − Additional strategies to induce reactivity between Ni II and O 2 include incorporation of (1) auxiliary ligands that undergo a chemical reaction upon O 2 addition (e.g., thioether/thiolate oxygenation, ,− C–C reductive elimination, ,,, radical pathways), (2) ligand sets that impart highly reduced Ni centers, providing a driving force for electron transfer, ,,− and (3) redox-active ligands to store reducing equivalents . Incorporation of directed secondary sphere interactions provides a complementary synthetic strategy to enhance binding of otherwise inert substrates to metal sites, a design principle routinely exploited by metalloenzymes. − Although secondary coordination sphere hydrogen bonding interactions have been extensively explored for dioxygen activation, − reactivity of O 2 with complexes bearing appended borane Lewis acids is underexplored and unknown with Ni. The oxophilicity and tunable Lewis acidity of boranes provide a unique strategy to enable stoichiometric and ultimately catalytic reactions of O 2 with Ni(II) in systems that would otherwise be inert.…”

Section: Introductionmentioning

confidence: 99%

Appended Lewis Acids Enable Dioxygen Reactivity and Catalytic Oxidations with Ni(II)

Beagan,

Rivera,

Szymczak

2024

J. Am. Chem. Soc.

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We disclose a suite of Ni(II) complexes featuring secondary sphere Lewis acids of varied Lewis acidity and tether lengths. Several of these complexes feature atypical behavior of Ni(II): reactivity with O 2 that occurs only in the presence of a tethered Lewis acid. In situ UV−vis spectroscopy revealed that, although adducts are stable at −40 °C, complexes containing 9borabicyclo[3.3.1]nonane (9-BBN) Lewis acids underwent irreversible oxidative deborylation when warmed to room temperature. We computationally and experimentally identified that oxidative instability of appended 9-BBN moieties can be mitigated using weaker Lewis acids such as pinacolborane (BPin). These insights enabled the realization of catalytic reactions: hydrogen atom abstraction from phenols and room temperature oxygen atom transfer to PPh 3 .

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Section: Introductionmentioning

confidence: 99%

Appended Lewis Acids Enable Dioxygen Reactivity and Catalytic Oxidations with Ni(II)

Beagan,

Rivera,

Szymczak

2024

J. Am. Chem. Soc.

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“…Metalloenzymes, in particular, have evolved exquisite secondary spheres comprising ensembles of interactions that accelerate reactions by many orders of magnitude. For instance, nearly all naturally occurring cytochrome P450 enzymes, which catalyze the difficult oxidation of C–H bonds, share an identical primary coordination sphere defined by a heme cofactor and a cysteine; however, it is their unique secondary coordination spheres that govern which substrates are oxidized and the selectivity of the oxidation. , The modular scaffolding provided by the protein backbone enables evolution to discover the precise placement of amino acid side chains in the secondary sphere.…”

Section: Introductionmentioning

confidence: 99%

Peptidic Scaffolds Enable Rapid and Multivariate Secondary Sphere Evolution for an Abiotic Metallocatalyst

et al. 2022

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Metalloenzymes have benefited from the iterative process of evolution to achieve the precise arrangements of secondary sphere non-covalent interactions that enhance metal-centered catalysis. Iterative synthesis of scaffolds that display complex secondary sphere elements in abiotic systems can be highly challenging and time-intensive. To overcome this synthetic bottleneck, we developed a highly modular and rapid synthetic strategy, leveraging the efficiency of solid-phase peptide synthesis and conformational control afforded by non-canonical residues to construct a ligand platform displaying up to four unique residues of varying electronics and sterics in the secondary coordination sphere. As a proof-of-concept that peptidic secondary sphere can cooperate with the metal complex, we applied this scaffold to a well-known, modestly active C–H oxidizing Fe catalyst to evolve specific non-covalent interactions that is more than double its catalytic activity. Solution-state NMR structures of several catalyst variants suggest that higher activity is correlated with a hydrophobic pocket above the Fe center that may enhance the formation of a catalyst–substrate complex. Above all, we show that peptides are a convenient, highly modular, and structurally defined ligand platform for creating secondary coordination spheres that comprise multiple, diverse functional groups.

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Synthesis, structural studies and solubility properties of zinc(II), nickel(II) and copper(II) complexes of bulky tris(triazolyl)borate ligands

Bongiovanni

Rowe

Fadden

et al. 2010

Inorganica Chimica Acta

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Beyond Heme‐Thiolate Interactions: Roles of the Secondary Coordination Sphere in Cytochrome P450 Systems

Cited by 3 publications

References 63 publications

Appended Lewis Acids Enable Dioxygen Reactivity and Catalytic Oxidations with Ni(II)

Appended Lewis Acids Enable Dioxygen Reactivity and Catalytic Oxidations with Ni(II)

Peptidic Scaffolds Enable Rapid and Multivariate Secondary Sphere Evolution for an Abiotic Metallocatalyst

Synthesis, structural studies and solubility properties of zinc(II), nickel(II) and copper(II) complexes of bulky tris(triazolyl)borate ligands

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