Dataset Information

Nacnac-Cobalt-Mediated P₄ Transformations.

ABSTRACT: A comparison of P₄ activations mediated by low-valent ?-diketiminato (L) cobalt complexes is presented. The formal Co⁰ source [K₂ (L³ Co)₂ (?₂ :?¹ ,?¹ -N₂ )] (1) reacts with P₄ to form a mixture of the monoanionic complexes [K(thf)₆ ][(L³ Co)₂ (?₂ :?⁴ ,?⁴ -P₄ )] (2) and [K(thf)₆ ][(L³ Co)₂ (?₂ :?³ ,?³ -P₃ )] (3). The analogue Co^I precursor [L³ Co(tol)] (4?a), however, selectively yields the corresponding neutral derivative [(L³ Co)₂ (?₂ :?⁴ ,?⁴ -P₄ )] (5?a). Compound 5?a undergoes thermal P atom loss to form the unprecedented complex [(L³ Co)₂ (?₂ :?³ ,?³ -P₃ )] (6). The products 2 and 3 can be obtained selectively by an one-electron reduction of their neutral precursors 5?a and 6, respectively. The electrochemical behaviour of 2, 3, 5?a, and 6 is monitored by cyclic voltammetry and their magnetism is examined by SQUID measurements and the Evans method. The initial Co^I -mediated P₄ activation is not influenced by applying the structurally different ligands L¹ and L² , which is proven by the formation of the isostructural products [(LCo)₂ (?₂ :?⁴ ,?⁴ -P₄ )] [L=L³ (5?a), L¹ (5?b), L² (5?c)].

SUBMITTER: Spitzer F

PROVIDER: S-EPMC5324690 | biostudies-literature | 2017 Feb

REPOSITORIES: biostudies-literature

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Publications

Nacnac-Cobalt-Mediated P4 Transformations.

Spitzer Fabian F Graßl Christian C Balázs Gábor G Mädl Eric E Keilwerth Martin M Zolnhofer Eva M EM Meyer Karsten K Scheer Manfred M

Chemistry (Weinheim an der Bergstrasse, Germany) 20170125 11

A comparison of P4 activations mediated by low-valent β-diketiminato (L) cobalt complexes is presented. The formal Co0 source [K2 (L3 Co)2 (μ2 :η1 ,η1 -N2 )] (1) reacts with P4 to form a mixture of the monoanionic complexes [K(thf)6 ][(L3 Co)2 (μ2 :η4 ,η4 -P4 )] (2) and [K(thf)6 ][(L3 Co)<s ...[more]

PMID: 28032678

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Project description:Oxidative O2 -dependent biotransformations are promising for chemical synthesis, but their development to an efficiency required in fine chemical manufacturing has proven difficult. General problem for process engineering of these systems is that thermodynamic and kinetic limitations on supplying O2 to the enzymatic reaction combine to create a complex bottleneck on conversion efficiency. We show here that continuous-flow microreactor technology offers a comprehensive solution. It does so by expanding the process window to the medium pressure range (here, ≤34 bar) and thus enables biotransformations to be conducted in a single liquid phase at boosted concentrations of the dissolved O2 (here, up to 43 mM). We take reactions of glucose oxidase and d-amino acid oxidase as exemplary cases to demonstrate that the pressurized microreactor presents a powerful engineering tool uniquely apt to overcome restrictions inherent to the individual O2 -dependent transformation considered. Using soluble enzymes in liquid flow, we show reaction rate enhancement (up to six-fold) due to the effect of elevated O2 concentrations on the oxidase kinetics. When additional catalase was used to recycle dissolved O2 from the H2 O2 released in the oxidase reaction, product formation was doubled compared to the O2 supplied, in the absence of transfer from a gas phase. A packed-bed reactor containing oxidase and catalase coimmobilized on porous beads was implemented to demonstrate catalyst recyclability and operational stability during continuous high-pressure conversion. Product concentrations of up to 80 mM were obtained at low residence times (1-4 min). Up to 360 reactor cycles were performed at constant product release and near-theoretical utilization of the O2 supplied. Therefore, we show that the pressurized microreactor is practical embodiment of a general reaction-engineering concept for process intensification in enzymatic conversions requiring O2 as the cosubstrate.

Dataset Information

Nacnac-Cobalt-Mediated P₄ Transformations.

Publications

Nacnac-Cobalt-Mediated P<sub>4</sub> Transformations.

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