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.
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 CC coupled dinuclear methoxide [(MeZn)2(tBu‐DAB‐DAB(H)‐tBu)(μ‐OMe)], the formation of which involves initial ZnOOMe 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.
Over the past 150 years,acertain mythology has arisen around the mechanistic pathwaysofthe oxygenation of organometallics with non-redox-active metal centers as well as the character of products formed. Notably,t here is aw idespread perception that the formation of commonly encountered metal alkoxide species results from the auto-oxidation reaction, in whichaparent metal alkylc ompound is oxidized by the metal alkylperoxide via oxygen transfer reaction. Now, harnessing awell-defined zinc ethylperoxide incorporating a bdiketiminate ligand, the investigated alkylperoxide compounds do not react with the parent metal alkyl complex as well as Et 2 Zn to form az inc alkoxide.U pon treatment of the zinc ethylperoxide with Et 2 Zn, ap reviously unobserved ligand exchange process is favored. Isolation of az inc hydroxide carboxylate as ap roduct of decomposition of the parent zinc ethylperoxide demonstrates the susceptibility of the latter to OÀ Ob ond homolysis.Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.
The first systematic theoretical and experimental studies of reaction systems involving ZnR(2) (R=Me, Et or tBu) with dibenzoyl (dbz) as a non-innocent ligand revealed that the character of the metal-bonded R group as well as the ratio of the reagents and the reaction temperature significantly modulate the reaction outcome. DFT calculations showed four stable minima for initial complexes formed between ZnR(2) and dbz and the most stable structure proved to be the 2:1 adduct; among the 1:1 adducts three structural isomers were found of which the most stable complex had the monodentate coordination mode and the chelate complex with the s-cis conformation of the dbz unit appeared to be the least stable form. Interestingly, the reaction involving ZnMe(2) did not lead to any alkylation product, whereas the employment of ZntBu(2) resulted in full conversion of dbz to the O-alkylated product [tBuZn{PhC(O)C(OtBu)Ph}] already at -20 °C. A more complicated system was revealed for the reaction of dbz with ZnEt(2). Treatment of a solution of dbz in toluene with one equivalent of ZnEt(2) at room temperature afforded a mixture of the O- and C-alkylated products [EtZn{PhC(O)C(OEt)Ph}] and [EtZn{OC(Ph)C(O)(Et)Ph}], respectively. The formation of the C-alkylated product was suppressed by decreasing the initial reaction temperature to -20 °C. Moreover, in the case of the dbz/ZnEt(2) system monitoring of the dbz conversion over the entire reaction course revealed a product inhibition effect, which highlights possible participation of multiple equilibria of different zinc alkoxide/ZnEt(2) aggregates. Diffusion NMR studies indicated that dbz forms an adduct with the O-alkylated product, which is a competent species for executing the inhibition of the alkylation event.
O, was für eine Reaktion: Die Oxygenierung von Me2Zn⋅tBu‐DAB (tBu‐DAB= 1,4‐Di‐tert‐butyl‐1,4‐diazabutadien) liefert das neuartige Oxo(methylperoxid)‐Cuban 1, das entsprechende doppelt cubische Oxo(methoxid) 2 und das C‐C‐verknüpfte zweikernige Methoxid [(MeZn)2(tBu‐DAB‐DAB(H)‐tBu)(μ‐OMe)], dessen Bildung mit der Homolyse einer ZnO‐OMe‐Bindung beginnt.
In the Full Paper by Lewiń ski et al., Figure 3 in the Results and Discussion section has been found to contain two mistakes. In Figure 3 a, the schematic representation of compound IV was incorrectly drawn and in Figure 3 b, structures III and IV were exchanged by mistake. The correct version of Figure 3 is presented below. The authors apologise for this oversight.
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