Issue 27, 2024

Oxidatively-induced C(sp3)–C(sp3) bond formation at a tucked-in iron(iii) complex

Abstract

Carbon–carbon (C–C) bond formation is a cornerstone of synthetic chemistry, relying on routes such as transition-metal mediated cross-coupling for the introduction of new carbon-based functionality. For {[M]n+–C} (M = metal) structural units, studies that offer well-defined relationships between metal oxidation state, hydrocarbon strain, and {[M]n+–C} bond thermochemistry are thus informative, providing a means to reliably access new product classes. Here, we show that one-electron oxidation of the iron tucked-in complex [(η6-C5Me4[double bond, length as m-dash]CH2)Fe(dnppe)] (dnppe = 1,2-bis(di-n-propylphosphino)ethane) results in C(sp3)–C(sp3) bond formation giving unique {Fe2} dimers. Freeze-quenched CW X-band EPR spectroscopy allowed for spectroscopic identification of the reactive [(η6-C5Me4[double bond, length as m-dash]CH2)Fe(dnppe)]+ intermediate. Density functional theory (DFT) calculations reveal a primarily Fe-centered radical and a weak {[Fe]–C} bond (BDE[Fe]–C = 24.5 kcal mol−1, c.f. BDEC–C(ethane) = 90 kcal mol−1). For comparison, a structurally analogous Fe(III) methyl complex was prepared, [Cp*Fe(dnppe)(CH3)]+ (Cp* = C5Me5), where C(sp3)–C(sp3) coupling was not observed, consistent with a larger calculated BDE[Fe]–C value of 47.8 kcal mol−1. These data are analogized to the simple hydrocarbons ethane and cyclopropane, where a strain-induced BDEC–C decrease of 33 kcal mol−1 is witnessed on cyclization.

Graphical abstract: Oxidatively-induced C(sp3)–C(sp3) bond formation at a tucked-in iron(iii) complex

Supplementary files

Article information

Article type
Edge Article
Submitted
20 May 2024
Accepted
06 Jun 2024
First published
14 Jun 2024
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY-NC license

Chem. Sci., 2024,15, 10359-10365

Oxidatively-induced C(sp3)–C(sp3) bond formation at a tucked-in iron(III) complex

J. A. Zurakowski, C. S. Durfy, N. B. Stocek, G. Fanchini and M. W. Drover, Chem. Sci., 2024, 15, 10359 DOI: 10.1039/D4SC03292F

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