posted on 2013-05-06, 00:00authored bySubramaniam Kuppuswamy, Tamara
M. Powers, Bruce M. Johnson, Mark W. Bezpalko, Carl K. Brozek, Bruce M. Foxman, Louise A. Berben, Christine M. Thomas
The tris(phosphinoamide)-bridged FeIIFeII diiron complex Fe(μ-iPrNPPh2)3Fe(η2-iPrNPPh2) (1) can be reduced
in the
absence or presence of PMe3 to generate the mixed-valence
FeIIFeI complexes Fe(μ-iPrNPPh2)3Fe(PPh2NHiPr) (2) or Fe(μ-iPrNPPh2)3Fe(PMe3) (3), respectively. Following a typical oxidative group transfer procedure,
treatment of 2 or 3 with organic azides
generates the mixed-valent FeIIFeIII imido complexes
Fe(iPrNPPh2)3FeNR
(R = tBu (4), Ad (5), 2,4,6-trimethylphenyl (6)). These complexes represent
the first examples of first-row bimetallic complexes featuring both
metal–ligand multiple bonds and metal–metal bonds. The
reduced complexes 2 and 3 and imido complexes 4–6 have been characterized via X-ray
crystallography, Mössbauer spectroscopy, cyclic voltammetry,
and SQUID magnetometry, and a theoretical description of the bonding
within these diiron complexes has been obtained using computational
methods. The effect of the metal–metal interaction on the electronic
structure and bonding in diiron imido complexes 4–6 is discussed in the context of similar monometallic iron
imido complexes.