Sterically directed nitronate complexes of 2,6-di-tert-butyl-4-nitrophenoxide with Cu(ii) and Zn(ii) and their H-atom transfer reactivity.
The bulky 2,6-di-tert-butyl-4-nitrophenolate ligand forms complexes with [TptBuCuII]+and [TptBuZnII]+binding via the nitro group in an unusual nitronato-quinone resonance form (TptBu= hydro-tris(3-tert-butyl-pyrazol-1-yl)borate). The Cu complex in the solid state has a five-coordinate κ2-nitronate structure, while the Zn analogue has a four-coordinate κ1-nitronate ligand. 4-Nitrophenol, without the 2,6-di-tert-butyl substituents, instead binds to [TptBuCuII]+through the phenolate oxygen. This difference in binding is very likely due to the steric difficulty in binding a 2,6-di-tert-butyl-phenolate ligand to the [TptBuMII]+unit. TptBuCuII(κ2-O2NtBu2C6H2O) reacts with the hydroxylamine TEMPO-H (2,2,6,6-tetramethylpiperidin-1-ol) by abstracting a hydrogen atom. This system thus shows an unusual sterically enforced transition metal-ligand binding motif and a copper-phenolate interaction that differs from what is typically observed in biological and chemical catalysis.
Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195-1700, USA and Laboratoire d'Electrochimie Moléculaire, Université Paris Diderot, Bâtiment Lavoisier, 15 rue Jean de Bäif, 75205 Paris Cedex 13, France.
Thomas R
http://orcid.org/0000-0003-4087-9243
TR
Porter
Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195-1700, USA.
Ellen C
EC
Hayes
Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195-1700, USA.
Werner
http://orcid.org/0000-0002-9100-4909
W
Kaminsky
Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195-1700, USA and Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, USA. james.mayer@yale.edu.
James M
JM
Mayer