“Oxidative Addition” to a Zirconium(IV) Redox-Active Ligand Complex

Abstract

A strategy to enable reactivity analogous to oxidative addition is presented for d 0 transition-metal complexes. The reaction of the redox-active ligand 2,4-di-tert-butyl-6-tert-butylamidophenolate (ap) with ZrCl 4 (THF) 2 affords the new complex Zr IV (ap) 2 (THF) 2 . This compound is formally zirconium(IV) and contains no d electrons; however, exposure of Zr IV (ap) 2 (THF) 2 to chlorine gas results in swift chlorine addition at the zirconium metal center via one-electron oxidation of each ap ligand. The diradical product, Zr IV Cl 2 (isq) 2 (isq ) 2,4-di-tert-butyl-6-tert-butyliminosemiquinone), has been characterized by X-ray crystallography, electron paramagnetic resonance spectroscopy, and SQUID magnetometery.

A Redox‐Active Ligand as a Reservoir for Protons and Electrons: O2 Reduction at Zirconium(IV)

“…Thus, in the reaction the ligands serve as an electron reservoir to help effect multielectron reactivity at a non-redox-active metal. Similar reactions with redox-active ligands have been elucidated for oxidative addition, [12][13][14] reductive elimination, [15] and nitrene trans- fer [16,17] reactivity at d 0 complexes of the group 4 and 5 metals. In this report, we extend this approach beyond the utilization of the ligands as just electron reservoirs to develop a redox-active ligand that serves as both an electron and proton reservoir for O 2 reduction.…”

Transition metal complexes with bulky 4,6-di-tert-butyl-N-aryl(alkyl)-o-iminobenzoquinonato ligands: Structure, EPR and magnetism

“…We have found only seven examples of such complexes in the literature. There is a nickel complex [Ni II (IBQ L4 ) 2 (OClO 3 ) 2 ] (36) [62], rhenium complex Re II (ISQ L2 ) 2 (CO) 2 (37) [61] and a number of zirconium complexes Zr IV (AP tBu ) 2 (THF) 2 (38), [63,64] (Scheme 12).…”

“…Oxidation of 38 by gaseous chlorine at −78 • C leads to the bis-o-iminobenzosemiquinonato product Zr IV (ISQ tBu ) 2 Cl 2 (39) [63]. The latter complex was also prepared by the oxidation of bis-o-amidophenolate complex 38 with PhICl 2 at low temperature and from ZrCl 4 and two equivalents of lithium o-iminobenzosemiquinone (ISQ tBu )Li.…”

Group IV Coordination Chemistry of a Tetradentate Redox‐Active Ligand in Two Oxidation States

“…[5] We have been interested in developing further the coordination and reaction chemistry of redox-active ligands with early transition metals in order to bring late-transition-metal reactions, such as oxidative addition, reductive elimination, and group transfer, to electrophilic d 0 metal complexes. Oxidative addition and reductive elimination have been established as viable reaction pathways for group IV redoxactive ligand complexes., [6,7] Halogens were found to react 2-= 4,6-di-tert-butyl-2-(tert-butylamido)phenolate}, resulting in ligand oxidation and halide addition to the metal atom. This reaction resembles a traditional oxidative addition sequence in that the halides add to the metal center; however, it is differentiated by the formal assignment of the reducing equivalents, which come from the amidophenolate ligands.…”

“…s, 4 H, thf), 6.35 (dd, 3 J HH = 9.0 and 3.6 Hz, 2 H, aryl-H), 7.52 (dd, 3 J HH = 9.0 and 3.6 Hz, 2 H, aryl-H), 7.63 (s, 2 H, aryl-H), 7.68 (s, 2 H, aryl-H) ppm. 13 3 ], 117.7 (aryl-C), 124.9 (aryl-C), 129.5 (aryl-C), 129.9 (aryl-C), 134.5 (aryl-C), 141.0 (aryl-C), 143.1 (aryl-C), 145.9 (aryl-C), 153.…”