An Azobenzenyl Anion Radical Complex of Magnesium: Synthesis, Structure, and Reactivity Studies

Abstract

Azobenzenyl anion radical complex of magnesium [HC(C(Me)N-2,6-PrCH)]Mg(PhNNPh) (THF) (2) was obtained for the first time through the reaction of [HC(C(Me)N-2,6-PrCH)]MgBr (1) with potassium graphite in the presence of azobenzene. Complex 2 is a useful electron-transfer reagent as shown by the reactivity with diphenyl disulfide, diphenyl diselenide, oxygen, sulfur, and MeSiN yielding the magnesium thiolate [HC(C(Me)N-2,6-PrCH)]Mg(SPh)(THF) (3), magnesium selenolate [HC(C(Me)N-2,6-PrCH)]Mg(SePh)(THF) (4), peroxido complex {[HC(C(Me)N-2,6-PrCH)]Mg(THF)}(μ-η-η-O) (5), persulfido complex {[HC(C(Me)N-2,6-PrCH)]Mg(THF)}(μ-η-η-S) (6), and azido complex [HC(C(Me)N-2,6-PrCH)]MgN (7), respectively. Furthermore, treatment of 2 with MeSiCHN results in a rearrangement product {[HC(C(Me)N-2,6-PrCH)]Mg[CNN(SiMe)]} (8).

An Isolable Magnesium(II)-Radical Dianion Complex

“…Very recently, Ren et al , and Gilliard et al reported the magnesium-bipyridine and -diazo complexes D – G . Analyses of the electronic structures reveal that the bipyridine and diazo ligands are in a radical anion state due to the redox-active properties, and the magnesium center is essentially in the +2 oxidation state.…”

“…6,17 Until now, no stable mononuclear magnesium(I) compounds have been isolated, although Schnockel et al showed that the metastable donor-stabilized magnesium(I) halides could be obtained in solution at low temperature. 18,19 Very recently, Ren et al 20,21 and Gilliard et al 22 reported the magnesium-bipyridine and -diazo complexes D−G. Analyses of the electronic structures reveal that the bipyridine and diazo ligands are in a radical anion state due to the redox-active properties, and the magnesium center is essentially in the +2 oxidation state.…”

Lithium and magnesium complexes by using pyridyl-pendanted unsymmetrical β-diketiminates: syntheses and application as catalysts for the hydroboration of carbonyl compounds

“…The bond angles around the metal centres are 106.28( 8 57 Complex 3 joins a family of magnesium complexes supported by β-diketiminate ligands. [58][59][60][61][62][63][64][65][66][67][68][69][70][71][72][73][74][75][76] Nevertheless, mag-…”

Stepwise Reduction at Magnesium and Beryllium: Cooperative Effects of Carbenes with Redox Non-Innocent α-Diimines

“…The most defining characteristic of group 2 organometallic compounds is the highly polarized M–R bond (M = alkaline earth element, R = organic fragment), due to the low electronegativity of the alkaline earth metals. This bond polarization means that group 2 organometallic compounds exhibit an interesting dichotomy of reactivity, in which the metal center can behave as a highly potent Lewis acid − and the organic fragment can behave as an exceptionally strong nucleophile or Lewis base for heterolytic bond activation. ,, Much of the recent work in the field of molecular group 2 chemistry has focused on exploiting the high reactivity of the metal centers in order to activate and functionalize energy-relevant targets such as O 2 , H 2 , CO, and CO 2 ,− and even recently to achieve the unprecedented nucleophilic alkylation of benzene. , …”

“…As an alternative to the aforementioned low-valent alkaline earth complexes, which contain a highly reactive formally reduced metal center, substantial progress has been achieved in the study of alkaline earth complexes containing redox non-innocent ligands including α-diimines ,,− and azobenzene . The use of redox active proxy ligands allows the metal center to maintain its strongly preferred 2+ oxidation state while allowing facile, reversible electron transfers at the ligand.…”