Details

Autor(en) / Beteiligte

• Lionetti, Davide
• Medvecz, Andrew J
• Ugrinova, Vesela
• Quiroz-Guzman, Mauricio
• Noll, Bruce C
• Brown, Seth N

Titel

Redox-Active Tripodal Aminetris(aryloxide) Complexes of Titanium(IV)

Ist Teil von

• Inorganic chemistry, 2010-05, Vol.49 (10), p.4687-4697

Ort / Verlag

United States: American Chemical Society

Erscheinungsjahr

2010

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• New sterically encumbered tripodal aminetris(aryloxide) ligands N(CH2C6H2-3- t Bu-5-X-2-OH)3 ( tBu,XLH3) with relatively electron-rich phenols are prepared by Mannich condensation (X = OCH3) or by a reductive amination/Hartwig−Buchwald amination sequence on the benzyl-protected bromosalicylaldehyde (X = N[C6H4-p-OCH3]2), followed by debenzylation using Pearlman’s catalyst (Pd(OH)2/C). The analogous dianisylamino-substituted compound lacking the tert-butyl group ortho to the phenol (H,An2NLH3) is also readily prepared. The ligands are metalated by titanium(IV) tert-butoxide to form the five-coordinate alkoxides LTi(O t Bu). Treatment of the tert-butoxides with aqueous HCl yields the five-coordinate chlorides LTiCl, and with acetylacetone gives the six-coordinate diketonates LTi(acac). The diketonate complexes tBu,XLTi(acac) show reversible ligand-based oxidations with first oxidation potentials of +0.57, +0.33, and −0.09 V (vs ferrocene/ferrocenium) for X = t Bu, MeO, and An2N, respectively. Both dianisylamine-substituted complexes R,An2NLTi(acac) (R = t Bu, H) show similar electrochemistry, with three one-electron oxidations closely spaced at ∼0 V and three oxidations due to removal of a second electron from each diarylaminoaryloxide arm at ∼ + 0.75 V. The new electron-rich tripodal ligands therefore have the capacity to release multiple electrons at unusually low potentials for aryloxide groups.