β‐Ketoimine ligands stabilize zinc compounds: The dimeric zinc alkylperoxide [{(LL)ZnOOEt}2] (where LL=HC{(CMe)(2,6‐iPr2C6H3N)}2) has been prepared and structurally characterized (see picture, Zn green, N blue, O red, C gray). This compound, which is formed by the insertion of dioxygen into the ZnEt bond, is very active in the epoxidation of enones.

Despite the fact that extensive research has been carried out, the oxygenation of alkyl magnesium species still remains a highly unexplored research area and significant uncertainties concerning the mechanism of these reactions and the composition of the resulting products persist. This case study compares the viability of the controlled oxygenation of alkylmagnesium complexes supported by β-diketiminates. The structural tracking of the reactivity of (N,N)MgR-type complexes towards O at low temperature showed that their oxygenation led exclusively to the formation of magnesium alkylperoxides (N,N)MgOOR. The results also highlight significant differences in the stability of the resulting alkylperoxides in solution and demonstrate that [(BDI)Mg(μ-η :η -OOBn)] (in which BDI=[(ArNCMe) CH] and Ar=C H iPr -2,6) can be easily transformed to the corresponding magnesium alkoxide [(BDI)MgOBn] at ambient temperature, whilst [( BDI)Mg(μ-OOtBu)] (in which BDI=[(ArNCMe) CH] and Ar=C H F -2,4,6) is stable under similar conditions. The observed selective oxygenation of (N,N)MgR-type complexes to the corresponding (N,N)MgOOR alkylperoxides strongly contradicts the widely accepted radical-chain mechanism for the oxygenation of the main-group-metal alkyls. Furthermore, either the observed transformation of the alkylperoxide [(BDI)MgOOBn] to the alkoxide [(BDI)MgOBn] as well as the formation of an intractable mixture of products in the control reaction between the alkylperoxide [( BDI)MgOOtBu] and the parent alkylmagnesium [( BDI)MgtBu] complex are not in line with the common wisdom that magnesium alkoxide complexes' formation results from the metathesis reaction between MgOOR and Mg-R species. In addition, a high catalytic activity of well-defined magnesium alkylperoxides, in combination with tert-butyl hydroperoxide (TBHP) as an oxygen source, in the epoxidation of trans-chalcone is presented.

The reaction of MMe3 with 1 molar equiv of N-phenylsalicylideneimine (HsaldPh) yields the O,N-chelate complexes Me2M(saldPh) (where M = Al (1), Ga (2), In (3)) in high yields. The reaction of 1 with γ-picoline results in a ligand redistribution reaction and the formation of the five-coordinate complex MeAl(saldPh)2 (4), while the gallium and indium compounds are stable in the presence of γ-picoline. The resulting compounds have been characterized in a solution by NMR and IR spectroscopy and cryoscopic molecular weight measurements, and their molecular and crystal structure have been determined by X-ray crystallography. Compounds 1 and 2 exist as monomeric tetrahedral complexes, while the indium analogue 3 is dimeric with the In2(μ-O)2 bridges and five-coordinate metal centers. The five-coordinate methylaluminum compound 4 exhibits trigonal-bipyramidal geometry of the metal center. The obtained results show that a Schiff base acts as a strongly coordinating chelate ligand and, in this regard, it resembles the symmetrical acetylacetonato ligand and related β-diketonates. An extended crystal structure analysis reveals that the isostructural crystalline complexes 1 and 2 comprise monomeric four-coordinate molecules linked by C−Himino···O hydrogen bonds, forming helical chains. Parallel left- and right-handed helices joined by C−H···π interactions give rise to the 3D extended tetragonal framework, with voids filled by solvent molecules. In the crystalline complex 4 the C−Haryl···O hydrogen bonds organize molecules into H-bonded dimers.

Reactions between O 2 and organometallics with non-redox-active metal centers have received continuous interest foro ver1 50 years, althoughs ignificant uncertainties concerningt he character and details of the actual mechanism of these reactions persist. Harnessingd inuclear threecoordinate alkylzinc derivatives of an N,N-coupled bis(b-diketimine) proligand (LH 2 )a sam odel system, we demonstrate for the first time that as light modification of the reaction conditions might have ad ramatic influence on the oxygenation reaction outcomes, leading to an unprecedented variety of products originating from as ingle reaction system,t hat is, partially and fully oxygenated zinc alkoxides,zinc alkylperoxides, and zinc hydroxide compounds. Our studies indicate that accessibility of the three-coordinate zinc center by the O 2 molecule, coupled with the lower reactivity of Zn-Me vs.

A novel organozinc initiator with a clear mechanistic signature for organic radical reactions has been developed.

O what a reaction: The oxygenation of Me2Zn⋅tBu‐DAB (tBu‐DAB=1,4‐di‐tert‐butyl‐1,4‐diazabutadiene) affords the unprecedented oxo(methylperoxide) cubane 1, the corresponding double cubic oxo(methoxide) 2, and the CC coupled dinuclear methoxide [(MeZn)2(tBu‐DAB‐DAB(H)‐tBu)(μ‐OMe)], the formation of which involves initial ZnOOMe bond homolysis.

The epoxidation of enones by zinc alkylperoxides is a challenging task receiving considerable attention in contemporary research; however, until now no welldefined zinc alkylperoxide based systems have been described. Here, a new catalytic method of epoxidation of enones in the presence of zinc alkylperoxides supported by N,N-bidentate ligands and tert-butyl hydroperoxide is reported. A new dimeric zinc alkylperoxide complex supported by an aminotroponiminate ligand is also presented. The studied catalytic systems show high activity in the epoxidation of trans-chalcone, and in the case of a chiral catalyst with the (S,S)-N,N′-bis(1-phenylethyl)aminotroponiminate ligand a moderate enantioselectivity was achieved.

β‐Ketoiminliganden stabilisieren Zinkkomplexe: Das dimere Zinkalkylperoxid [{(LL)ZnOOEt}2] (LL=HC{(CMe)(2,6‐iPr2C6H3N)}2) wurde isoliert und strukturell charakterisiert (siehe Bild, Zn grün, N blau, O rot, C grau). Der Komplex, der durch Insertion von Disauerstoff in die Zn‐Et‐Bindung gebildet wird, ist hoch aktiv in der Epoxidierung von Enonen.