Studies on bis(3,5-di-t-butyl-1,2-benzoquinone 1-oximato)manganese(II) and its mixed-ligand complexes

Abstract

The synthesis, spectroscopy, and redox-reactivity towards PPh3 of bis(3,5-di-t-butyl-1,2-benzoquinone 1-oximato)manganese(II), Mn(OX)2, and its mixed-ligand complexes, Mn(ox)L-x [L-x = 8-hydroxyquinolinato (L-1) 2,2'-bipyridine (bpy) (L-2), 1,10-Phenanthroline (phen) (L-3) and N-(2-hydroxyphenyl)-3,5-di-t-butylsalicylaldiminato (L-4)] complexes, are presented. While some complexes exhibit solid-state ESR spectra they were ESR-silent in toluene or CHCl3 at 300 K. The reduction of all ESR-silent complexes with an excess of PPh3, independently from the nature of secondary L-x ligands, results in the appearance of a six-line hyperfine coupling of Mn-55 (I = 5/2) (A(Mn) = 95-100 G) and a seven-line radical signal, which was assigned to phosphiniminophenoxyl type radicals (g = 2.0056-2.0075, A(P) = 8.5 G and A(N) = 1.875 G). (C) 2002 Elsevier Science B.V. All rights reserved.