Issue 9, 2020

Spin state and reactivity of iron(iv)oxido complexes with tetradentate bispidine ligands

Abstract

The iron(IV)oxido complex [(bispidine)FeIV[double bond, length as m-dash]O(Cl)]+ is shown by experiment and high-level DLPNO-CCSD(T) quantum-chemical calculations to be an extremely short-lived and very reactive intermediate-spin (S = 1) species. At temperatures as low as −90 °C, it decays with a half-life of approx. two minutes, and this is the reason why, so far, it remained undetected and why it is extremely difficult to trap and fully characterize this interesting and extremely efficient oxidant. The large difference in reactivity between [(bispidine)FeIV[double bond, length as m-dash]O(Cl)]+ and [(bispidine)FeIV[double bond, length as m-dash]O(MeCN)]2+ (at least two orders of magnitude), while both oxido-iron(IV) complexes have very similar structures and an S = 1 electronic ground state, is presumably due to the large difference in the energy gap between the triplet and quintet electronic states. In presence of cyclohexane as substrate, [(bispidine)FeIV[double bond, length as m-dash]O(Cl)]+ oxidizes cyclohexane with a rate that is approx. 25 times faster than the self-decay of the oxidant, and selectively leads to chlorocyclohexane in moderate yield. The S = 1 electronic ground state of [(bispidine)FeIV[double bond, length as m-dash]O(Cl)]+ and a relatively low gap to the S = 2 state (approx. 6 kJ mol−1vs. approx. 75 kJ mol−1 for [(bispidine)FeIV[double bond, length as m-dash]O(MeCN)]2+) is also predicted by DLPNO-CCSD(T) quantum-chemical calculations. The method used was benchmarked with a set of six ferryl complexes with experimentally known electronic ground states.

Graphical abstract: Spin state and reactivity of iron(iv)oxido complexes with tetradentate bispidine ligands

Supplementary files

Article information

Article type
Paper
Submitted
29 nov 2019
Accepted
07 feb 2020
First published
07 feb 2020

Dalton Trans., 2020,49, 2888-2894

Spin state and reactivity of iron(IV)oxido complexes with tetradentate bispidine ligands

P. Comba, D. Faltermeier, S. Krieg, B. Martin and G. Rajaraman, Dalton Trans., 2020, 49, 2888 DOI: 10.1039/C9DT04578C

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements