2,2′-Pyridylpyrrolide Ligand Redistribution Following Reduction
journal contribution
posted on 2013-05-06, 00:00 authored by Keith Searles, Atanu K. Das, René W. Buell, Maren Pink, Chun-Hsing Chen, Kuntal Pal, David Gene Morgan, Daniel J. Mindiola, Kenneth G. CaultonThe potential redox activity of the
2,2′-pyridylpyrrolide
ligand carrying two CF<sub>3</sub> substituents (L<sup>2</sup>) is
investigated. Synthesis and characterization of d<sup>6</sup> and
d<sup>7</sup> species M(L<sup>2</sup>)<sub>2</sub> for M = Fe and
Co are described (both are nonplanar, but not tetrahedral), as are
the Lewis acidity of each. In spite of CV evidence for quasireversible
reductions to form M(L<sup>2</sup>)<sub>2</sub><sup><i>q</i>–</sup> where <i>q</i> = 1 and 2, chemical reductants
instead yield divalent metal complexes KM(L<sup>2</sup>)<sub>3</sub>, which show attractive interactions of K<sup>+</sup> to pyrrolide,
to F, and to lattice toluene π cloud. The collected evidence
on these products indicates that pyridylpyrrolide is a weak field
ligand here, but CO can force spin pairing in Fe(L<sup>2</sup>)<sub>2</sub>(CO)<sub>2</sub>. Evidence is presented that the overall reductive
reaction yields 33 mol % of bulk metal, which is the fate of the reducing
equivalents, and a mechanism for this ligand redistribution is proposed.
Analogous ligand redistribution behavior is also seen for nickel and
for trimeric monovalent copper analogues; reduction of Cu(L<sup>2</sup>)<sub>2</sub> simply forms Cu(L<sup>2</sup>)<sub>2</sub><sup>–</sup>.
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