52777-93-2Relevant articles and documents
Resurgence of Organomanganese(I) Chemistry. Bidentate Manganese(I) Phosphine-Phenol(ate) Complexes
Kadassery, Karthika J.,MacMillan, Samantha N.,Lacy, David C.
, p. 10527 - 10535 (2019/07/08)
As part of the United Nations 2019 celebration of the periodic table of elements, we are privileged to present our studies with the element manganese in this Forum Article series. Catalysis with organomanganese(I) complexes has recently emerged as an important area with the discovery that pincer manganese(I) complexes that can activate substrates through metal-ligand cooperative mechanisms are active (de)hydrogenation catalysts. However, this rapidly growing field faces several challenges, and we identify these in this Forum Article. Some of our efforts in addressing these challenges include using alternative precursors to Mn(CO)5Br to prepare manganese(I) dicarbonyl complexes, the latter of which is usually a component of active catalysts. Specifically, the synthesis of a new bidentate phosphine-phenol ligand along with its corresponding coordination chemistry of five new manganese(I) complexes is described. The complexes having two phenol-phenolate moieties interact with the secondary coordination sphere to enable facile loss of the bromido ligand and even one of the CO ligands to afford manganese(I) dicarbonyl centers.
New bis(aryloxy)-Ti(iv) complexes and their use for the selective dimerization of ethylene to 1-butene
Grasset, Fabien,Cazaux, Jean-Benoit,Magna, Lionel,Oliver-Bourbigou, Helene,Braunstein, Pierre
, p. 10396 - 10404,9 (2020/08/31)
New titanium complexes of general formula [(ArO)nTi(Oi-Pr) (4-n)] were synthesized and used as pre-catalysts for the selective dimerization of ethylene to 1-butene. The complexes were prepared in cyclohexane using [Ti(Oi-Pr)4] and one or two equivalents of the corresponding phenols (ArOH) at room temperature. In this work, both monodentate and chelating phenols were evaluated. For alkyl-substituted phenols, it was demonstrated that large steric hindrance at both ortho and ortho′ positions selectively yielded the mono-substituted complexes [(ArO)Ti(Oi-Pr)3]. Substitution at only one of the ortho positions allowed both the mono- and the di-substituted Ti complexes to be isolated. When a heteroatom was introduced on the phenol backbone, di-substitution systematically occurred except with phenols presenting a hemilabile -CH2NR2 group at the ortho position. Upon activation with 3 equiv. of AlEt3 at 20 bar and 60 °C, all the complexes selectively dimerized ethylene to 1-butene (>86% of butenes among which 99% of 1-butene). An increase of the steric bulk at the ortho position of the ligand or the introduction of a functional group led to decreased activity compared to [Ti(Oi-Pr)4].
Heterocyclic Spirocyclohexadienones from Substituted Phenols
Moehrle, H.,Schake, D.
, p. 1859 - 1868 (2007/10/03)
Mannich bases were prepared from substituted phenols with aliphatic amines and formaldehyde.Amine exchange with N-methyl-2-naphthylamine followed by a Hofmann Martius rearrangement gave rise to o,o'-amino-hydroxy-diphenylmethane derivatives.Under cyclization conditions some of these compounds produced spirocyclohexadienones, which are the ipso analogs to the hypothetic intermediates postulated in the aminomethylation mechanism of phenols. - Keywords: Mannich Reaction; Phenol Dienone Tautomerism; Hofmann Martius Rearrangement
