ic300733j_si_001.pdf (3.53 MB)
Ligand Effects on the Oxidative Addition of Halogens to (dpp-nacnacR)Rh(phdi)
journal contribution
posted on 2012-11-19, 00:00 authored by David
W. Shaffer, Scott A. Ryken, Ryan A. Zarkesh, Alan F. HeydukThe treatment of (dpp-nacnacR)Rh(phdi) {(dpp-nacnacR)− = CH[C(R)(N-iPr2C6H3)]2–; R = CH3, CF3; phdi = 9,10-phenanthrenediimine}
with X2 oxidants afforded octahedral rhodium(III) products
in the case of X = Cl and Br. The octahedral complexes exhibit well-behaved
cyclic voltammograms in which a two-electron reduction is observed
to regenerate the initial rhodium(I) complex. When treated with I2, (dpp-nacnacCH3)Rh(phdi) produced a square pyramidal
η1-I2 complex, which was characterized
by NMR and UV–vis spectroscopies, mass spectrometry, and X-ray
crystallography. The more electron poor complex (dpp-nacnacCF3)Rh(phdi) reacted with I2 to give a mixture of two products
that were identified by 1H NMR spectroscopy as a square
pyramidal η1-I2 complex and an octahedral
diiodide complex. Reaction of the square pyramidal (dpp-nacnacCH3)Rh(I2)(phdi) with HBF4 resulted in
protonation of the (dpp-nacnacCH3)− backbone
to provide an octahedral rhodium(III) diiodide species. These reactions
highlight the impact that changes in the electron-withdrawing nature
of the supporting ligands can have on the reactivity at the metal
center.