Ligand Effects on the Oxidative Addition of Halogens to (dpp-nacnacR)Rh(phdi)

By Shaffer, David W.; Ryken, Scott A.; Zarkesh, Ryan A. & Heyduk, Alan F.
Published in Inorganic Chemistry NULL 2012

Abstract

The 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.

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