Investigations of Iridium-Mediated Reversible C−H Bond Cleavage: Characterization of a 16-Electron Iridium(III) Methyl Hydride Complex

2009 ◽  
Vol 131 (24) ◽  
pp. 8603-8613 ◽  
Author(s):  
Wesley H. Bernskoetter ◽  
Susan Kloek Hanson ◽  
Sara K. Buzak ◽  
Zoe Davis ◽  
Peter S. White ◽  
...  
Keyword(s):  
Bond Cleavage ◽  
Hydride Complex

A general synthesis approach in action: preparation and characterization of polyoxomolybdenum(vi) organophosphonates through oxidative Mo–Mo bond cleavage in {MoV2O4}

CrystEngComm ◽  
2012 ◽  
Vol 14 (14) ◽  
pp. 4826 ◽  
Author(s):  
Lijuan Zhang ◽  
Jingmei Sun ◽  
Yunshan Zhou ◽  
Sadaf ul Hassan ◽  
Enbo Wang ◽  
...  
Keyword(s):  
Bond Cleavage ◽  
Action Preparation ◽  
General Synthesis ◽  
Synthesis Approach

scholarly journals Unveiling the crucial intermediates in androgen production

2015 ◽  
Vol 112 (52) ◽  
pp. 15856-15861 ◽  
Author(s):  
Piotr J. Mak ◽  
Michael C. Gregory ◽  
Ilia G. Denisov ◽  
Stephen G. Sligar ◽  
James R. Kincaid
Keyword(s):  
Bond Cleavage ◽  
Nucleophilic Attack ◽  
Reaction Intermediates ◽  
Structural Determinants ◽  
Initial Product ◽  
Androgen Synthesis ◽  
Ferric Peroxo ◽  
Enzymatic Mechanisms ◽  
Primary Substrate

Ablation of androgen production through surgery is one strategy against prostate cancer, with the current focus placed on pharmaceutical intervention to restrict androgen synthesis selectively, an endeavor that could benefit from the enhanced understanding of enzymatic mechanisms that derives from characterization of key reaction intermediates. The multifunctional cytochrome P450 17A1 (CYP17A1) first catalyzes the typical hydroxylation of its primary substrate, pregnenolone (PREG) and then also orchestrates a remarkable C17–C20 bond cleavage (lyase) reaction, converting the 17-hydroxypregnenolone initial product to dehydroepiandrosterone, a process representing the first committed step in the biosynthesis of androgens. Now, we report the capture and structural characterization of intermediates produced during this lyase step: an initial peroxo-anion intermediate, poised for nucleophilic attack on the C20 position by a substrate-associated H-bond, and the crucial ferric peroxo-hemiacetal intermediate that precedes carbon–carbon (C-C) bond cleavage. These studies provide a rare glimpse at the actual structural determinants of a chemical transformation that carries profound physiological consequences.

scholarly journals Crystallization and preliminary X-ray characterization of the 2,4′-dihydroxyacetophenone dioxygenase fromAlcaligenessp. 4HAP

2014 ◽  
Vol 70 (6) ◽  
pp. 823-826 ◽  
Author(s):  
G. Beaven ◽  
A. Bowyer ◽  
P. Erskine ◽  
S. P. Wood ◽  
A. McCoy ◽  
...  
Keyword(s):  
Synchrotron Radiation ◽  
Formic Acid ◽  
Molecular Oxygen ◽  
Aromatic Ring ◽  
Bond Cleavage ◽  
Its Sequence ◽  
Hydroxybenzoic Acid ◽  
X Ray

The enzyme 2,4′-dihydroxyacetophenone dioxygenase (or DAD) catalyses the conversion of 2,4′-dihydroxyacetophenone to 4-hydroxybenzoic acid and formic acid with the incorporation of molecular oxygen. Whilst the vast majority of dioxygenases cleave within the aromatic ring of the substrate, DAD is very unusual in that it is involved in C—C bond cleavage in a substituent of the aromatic ring. There is evidence that the enzyme is a homotetramer of 20.3 kDa subunits each containing nonhaem iron and its sequence suggests that it belongs to the cupin family of dioxygenases. By the use of limited chymotrypsinolysis, the DAD enzyme fromAlcaligenessp. 4HAP has been crystallized in a form that diffracts synchrotron radiation to a resolution of 2.2 Å.

scholarly journals Vibrational characterization of a diiron bridging hydride complex – a model for hydrogen catalysis

2020 ◽  
Vol 11 (21) ◽  
pp. 5487-5493 ◽  
Author(s):  
Leland B. Gee ◽  
Vladimir Pelmenschikov ◽  
Hongxin Wang ◽  
Nakul Mishra ◽  
Yu-Chiao Liu ◽  
...  
Keyword(s):  
Dft Calculations ◽  
Model Systems ◽  
Hydride Complex ◽  
Vibrational Characterization

Fe–H–Fe bridging iron hydrides in model systems and metalloenzymes: benefits and challenges in revealing their vibrational signatures using NRVS spectroscopy and DFT calculations.

scholarly journals Synthesis and Characterization of New Diiron and Diruthenium μ-Aminocarbyne Complexes Containing Terminal S-, P- and C-Ligands

2007 ◽  
Vol 62 (3) ◽  
pp. 427-438 ◽  
Author(s):  
Vincenzo G. Albano ◽  
Luigi Busetto ◽  
Fabio Marchetti ◽  
Magda Monari ◽  
Stefano Zacchini ◽  
...  
Keyword(s):  
Molecular Structure ◽  
Diffraction Study ◽  
Coordination Mode ◽  
Bond Cleavage ◽  
Synthesis And Characterization ◽  
X Ray Diffraction ◽  
X Ray ◽  
Dithiocarbamate Ligand ◽  
High Yields

The diiron aminocarbyne complexes [Fe2{μ-CN(Me)(R)}(μ-CO)(CO)(NCMe)(Cp)2][SO3CF3] (R = Xy1, 1a; R = Me, 1b; R = CH2Ph, 1c; Xy1 = 2,6-Me2C6H3) undergo replacement of the coordinated nitrile by halides, diethyldithiocarbamate, and dicyanomethanide to give [Fe2{μ-CN(Me) (R)}(μ-CO)(CO)(X)(Cp)2] complexes (R = Me, X = Br, 4a; R = Me, X = I, 4b; R = CH2Ph, X = Cl, 4c; R = CH2Ph, X = Br, 4d; R = CH2Ph, X = I, 4e; R = Xy1, X = SC(S)NEt2, 5a; R = Me, X = SC(S)NEt2, 5b; R = Xy1, X = CH(CN)2, 7), in good yields. The molecular structure of 5a shows an unusual η1 coordination mode of the dithiocarbamate ligand. Similarly, treatment of [M2{μ-CN(Me) (R)}(μ-CO)(CO)(NCMe)(Cp)2][SO3CF3] (M = Fe, R = Xy1, 1a; M = Fe, R = Me, 1b; M = Ru, R = Xy1, 2a; M = Ru, R = Me, 2b) with a series of phosphanes generates the cationic complexes [M2{μ- CN(Me)(R)}(μ-CO)(CO)(P)(Cp)2][SO3CF3] (M = Fe, R = Xy1, P = PPh2H, 6a; M = Fe, R = Xy1, P = PPh3, 6b; M = Fe, R = Xy1, P = PMe3, 6c; M = Fe, R = Me, P = PMe2Ph, 6d; M = Fe, R = Me, P = PPh3, 6e; M = Fe, R = Me, P = PMePh2, 6f; M = Ru, R = Xy1, P = PPh2H, 6g; M = Ru, R = Me, P = PPh2H, 6h), in high yields. The molecular structure of 6a has been elucidated by an X-ray diffraction study. The reactions of [Fe2{μ-CN(Me)(Xyl)}(μ-CO)(CO)(NCR′)(Cp)2][SO3CF3] [R′ = Me, 1a; R′ = tBu, 3] with PhLi and PPh2Li yield [Fe2{μ-CN(Me)(Xy1)}(μ-CO)(CO)(Ph)(Cp)2] (8) and [Fe2{μ-CN(Me)(Xy1)}(μ-CO)(CO)(PPh2)(Cp)2] (9), respectively. The molecular structure of 8 has been ascertained by X-ray diffraction. Conversely, the reaction of 1a with MeLi generates the aminoalkylidene compound [Fe2{C(Me)N(Me)(Xy1)}(μ-CO)2(CO)(Cp)2] (10).Finally, the acetone complex [Fe2{μ-CN(Me)(Xy1)}(μ-CO)(CO)(OCMe2)(Cp)2][SO3CF3] (12) reacts with lithium acetylides to give complexes [Fe2{μ-CN(Me)(Xy1)}(μ-CO)(CO)(C≡CR)(Cp)2] (R = p-C6H4Me, 11a; R = Ph, 11b; R = SiMe3, 11c), in high yields. Filtration through alumina of a solution of 11a in CH2Cl2 results in hydration of the acetylide group and C-Si bond cleavage, affording [Fe2{μ-CN(Me)(Xy1)}(μ-CO)(CO){C(O)Me}(Cp)2] (12).

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