Developing catalytic applications of cooperative bimetallics: competitive hydroamination/trimerization reactions of isocyanates catalysed by sodium magnesiates

Abstract

Mixed-metal reagents [NaMg(CH2SiMe3)3] (1) and [(THF)NaMg(NPh2)3(THF)] [3-(THF)(2)] can act as precatalysts to selectively promote the hydroamination/trimerization of isocyanates (RNCO) depending on the steric bulk of the R substituent.

Structural and Mechanistic Insights into s‐Block Bimetallic Catalysis: Sodium Magnesiate‐Catalyzed Guanylation of Amines

“…www.chemeurj.org 2016 Wiley-VCH Verlag GmbH &Co. KGaA, Weinheim which are consistent with the presence in solution of monoanionic [(THF) 3 NaMg 2 (NHAr) 6 ] À (5A;( M r = 769.66 gmol À1 )a nd dianionic [Mg 2 (NHAr)6 ] 2À (5B; M r = 1008.97gmol À1 )s pecies (1 %e rror for both species) [25]. Scheme4.Proposed magnesiate species 5A and 5B observed in [D 8 ]THF.…”

“…[21] Three molecules of THF complete the coordinations phere of each sodium atom, which is also coordinated by two amido groups with NaÀNc ontacts (mean value 2.54(4) )t hat are significantly elongated compared with that reported for the homometal-lic sodium anilide [{(PMDETA)NaNHPh} 2 ]( meanv alue 2.42(3) ). [6] Multinuclear NMR spectroscopy characterization of compound 5 was performed in C 6 D 6 . Compound 6 results from as imilar reactiono f1 with three equivalents of diphenylamine, and displays am onomeric arrangement in which the amido groups coordinate terminallyt oM gt hrough their N atoms; whereas the Na center has p interactions with two phenylgroups in addition to binding to two THF ligands.…”

“…[6,19,37] LiCH 2 SiMe 3 ,a mines, phosphines, and carbodiimides were purchased from Sigma-Aldrich and used as received. Hexane, benzene, and THF were dried by heating to reflux over sodium benzophenone ketyl and distilled under nitrogen or were passed through ac olumn of activated alumina (Innovative Te ch.…”

“…Most initiala pplications have involved the hydroamination of unsaturated organic substrates,s uch as alkenesa nd alkynes, in which heavier Ca or Sr complexes have demonstratedr emarkable catalytic capabilities. [6] Cooperativee ffects betweent he two metals underpin this catalytic transformation, [7] in whichL ewis acidicN aa nchors and activates the isocyanate to enable intramolecular attack by the highly nucleophilic Lewis basic tris(amido) magnesiate, which facilitates as ynergistic scenariot hat is not availableinthe aforementioned single-metal systems. [5] To overturn this trend, we have shown recently that Mg activated within asodium magnesiate platform can outperform Ca and Ba systemsi nt he hydroamination of isocyanates, secureh ighery ields, and show superior substrate scope under milderc onditions.…”

Backbone Reactivity of Lithium β‐Diketiminate (NacNac) Complexes with CO2, tBuNCO and iPrNCO

“…The lithium centrei sb onded to an oxygen from each symmetry equivalent carboxylate unit [LiÀO 1 1.867 (7) ;L i ÀO 2 ' 1.923 (5) ]. CÀOb ond distances in the carboxylate unit are elongated comparedt ot hose in the parentC O 2 molecule (1.1615 ), [22] indicating significant p-delocalisation within the CO 2 moiety [C 30 ÀO 1 and C 30 ÀO 2 distances are 1.245(4) and 1.250(4) respectively].S uch elongation of CÀOb onds has been observed in several studies of carboxylates, all of which contained bonds of similarl ength to those in 1. [23] Of special interest in 1 is the fact that the CO 2 does not insert into the seemingly more reactive LiÀNb ond present in the alkali metal complex, instead redistributingt ot he NacNac backbonea nd forming an ew carbon-carbon bond, providing on one hand carboxylate functionality in the backbone at the g-carbonp osition, and on the other hand diimine (C=N) functionality in the main body of the NacNac ligand ( Figure 3).…”