A New Spin on Cyclooctatetraene (COT) Redox Activity:
Low-Spin Iron(I) Complexes That Exhibit Antiferromagnetic Coupling
to a Singly Reduced η<sup>4</sup>‑COT Ligand
Tufan
K. Mukhopadhyay
Marco Flores
Russell K. Feller
Brian L. Scott
R. Dean Taylor
Moshe Paz-Pasternak
Neil J. Henson
Francisca N. Rein
Nathan C. Smythe
Ryan J. Trovitch
John C. Gordon
10.1021/om500909h.s002
https://acs.figshare.com/articles/dataset/A_New_Spin_on_Cyclooctatetraene_COT_Redox_Activity_Low_Spin_Iron_I_Complexes_That_Exhibit_Antiferromagnetic_Coupling_to_a_Singly_Reduced_sup_4_sup_COT_Ligand/2223403
Formally
zerovalent (κ<sup>3</sup>-phosphine)Fe(η<sup>4</sup>-COT)
complexes supported by either Triphos (PhP(CH<sub>2</sub>CH<sub>2</sub>PPh<sub>2</sub>)<sub>2</sub>) or Triphos* (H<sub>3</sub>CC(CH<sub>2</sub>PPh<sub>2</sub>)<sub>3</sub>) have been prepared
following chelate addition to (COT)<sub>2</sub>Fe (COT = 1,3,5,7-cyclooctatetraene)
and by reduction of the respective dibromide complexes in the presence
of excess COT. The solid-state structure of each complex was determined
by single-crystal X-ray diffraction, and close inspection of the metrical
parameters revealed significant COT ligand reduction, independent
of the coordination geometry about iron. While the neutral and dianionic
forms of the redox-active COT ligand have historically received a
great deal of attention, a dearth of information regarding the often-evoked
radical monoanion form of this ligand prompted the full electronic
structure investigation of these complexes using a range of techniques.
Comparison of the Mössbauer spectroscopic data collected for
both (Triphos)Fe(η<sup>4</sup>-COT) complexes with data obtained
for two appropriate reference compounds indicated that they possess
a low-spin Fe(I) center that is antiferromagnetically coupled to a
COT radical monoanion. Further evidence for this electronic structure
determination by EPR spectroscopy and cyclic voltammetry is presented.
A comparison of the solid-state metrical parameters determined in
this study to those of related first-row transition-metal complexes
has provided insight into the electronic structure analysis of related
organometallic complexes.
2014-12-22 00:00:00
COT ligand reduction
Redox Activity
cyclic voltammetry
dianionic forms
structure investigation
EPR spectroscopy
Exhibit Antiferromagnetic
dibromide complexes
structure analysis
organometallic complexes
New Spin
reference compounds
coordination geometry
chelate addition
Tripho
monoanion form
H 3CC
structure determination