Homotropic cooperativity in iron-catalyzed alkyne cyclotrimerizations

Geer, Ana M., Navarro, Janeth, Alamán-Valtierra, Pablo, Coles, Nathan T. ORCID: https://orcid.org/0000-0001-6190-9080, Kays, Deborah L. ORCID: https://orcid.org/0000-0002-4616-6001 and Tejel, Cristina 2023. Homotropic cooperativity in iron-catalyzed alkyne cyclotrimerizations. ACS Catalysis 13 (10) , 6610–6618. 10.1021/acscatal.3c00764

Preview

PDF - Published Version Available under License Creative Commons Attribution. Download (3MB) | Preview

Abstract

Enhancing catalytic activity through synergic effects is a current challenge in homogeneous catalysis. In addition to the well-established metal–metal and metal–ligand cooperation, we showcase here an example of self-activation by the substrate in controlling the catalytic activity of the two-coordinate iron complex [Fe(2,6-Xyl2C6H3)2] (1, Xyl = 2,6-Me2C6H3). This behavior was observed for aryl acetylenes in their regioselective cyclotrimerization to 1,2,4-(aryl)-benzenes. Two kinetically distinct regimes are observed dependent upon the substrate-to-catalyst ratio ([RC≡CH]0/[1]0), referred to as the low ([RC≡CH]0/[1]0 < 40) and high ([RC≡CH]0/[1]0 > 40) regimes. Both showed sigmoidal kinetic response, with positive Hill indices of 1.85 and 3.62, respectively, and nonlinear Lineweaver–Burk replots with an upward curvature, which supports positive substrate cooperativity. Moreover, two alkyne molecules participate in the low regime, whereas up to four are involved in the high regime. The second-order rate dependence on 1 indicates that binuclear complexes are the catalytically competent species in both regimes, with that in the high one being 6 times faster than that involved in the low one. Moreover, Eyring plot analyses revealed two different catalytic cycles, with a rate-determining step more endergonic in the low regime than in the high one, but with a more ordered transition state in the high regime than in the low one.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Chemistry
Publisher:	American Chemical Society
ISSN:	2155-5435
Date of First Compliant Deposit:	7 August 2024
Date of Acceptance:	28 April 2023
Last Modified:	25 Oct 2024 13:22
URI:	https://orca.cardiff.ac.uk/id/eprint/170302

Actions (repository staff only)

Edit Item