Synthesis and characterisation of a series of alkylmagnesium amide and related oxygen-contaminated “alkoxy” compounds

Abstract

Synthesised either by an unusual tert-butyl metathesis between tert-butyllithium and a n,s-butylmagnesium amide or by reaction of an alkyl Grignard reagent and a sodium amide, five tert-butylmagnesium amides, Bu(t)MgDBA (5)(DBA=dibenzylamide), Bu(t)MgDA (6)(DA=diisopropylamide), Bu(t)MgHMDS (7)(HMDS=1,1,1,3,3,3-hexamethyldisilazide), Bu(t)MgTMP (8)(TMP=2,2,6,6-tetramethylpiperidide) and Bu(t)MgNCy2 (9)(cy=cyclohexyl) have been isolated as crystalline solids. All five amides have been characterised by X-ray crystallography and solution NMR spectroscopic studies. The former studies reveal a common dimeric molecular structure with amido bridges in a planar (MgN)2 ring and terminal Bu(t) ligands on the Mg atoms. Also described is the dodecameric primary amide [Bu(n)MgN(H)Dipp]12 (10a) and its monomeric solvate Bu(n)MgN(H)Dipp.TMEDA (10b)(Dipp=2,6-diisopropylphenyl; TMEDA=N,N,N',N'-tetramethylethylenediamine). The crystal structures of the oxo-insertion products Bu(t)MgOBu(t).THF (11), Bu(t)Mg(mu-OBu(t))(mu-TMP)MgTMP (12) and Mg(OBu(n))HMDS.solv [solv=THF (13a) or Et2O (13b)], made fortuitously during the course of this work, are also presented.

Advances in alkaline earth-nitrogen chemistry

“…where the larger amide ligands bridge the metal centers [105]. In the case of the TMP ligand, agostic interactions were observed arising from the methyl groups of the bridging ligand.…”

Oxygenation Chemistry of Magnesium Alkyls Incorporating β‐Diketiminate Ligands Revisited

“…In this instance, the reaction was conducted ac-Chem. [19] We also investigatedt he oxygenationo fb enzylmagnesium complex 1c under various conditions. 2016, 22,17776 -17783 www.chemeurj.org 2016 Wiley-VCH Verlag GmbH &Co. KGaA, Weinheim cording to the slightly modified Bailey's procedure by controlled exposure of the corresponding alkylmagnesium complex to an excess of dry dioxygen at À20 8Cf or 1h.T he desired alkylperoxide[ ( F3 BDI)Mg(m-OOtBu)] 2 (2b)w as isolated in high yield as light-yellow crystals( Figure 1b).…”

Synthesis of an alkylmagnesium amide and interception of a ring-opened isomer of the important utility amide 2,2,6,6-tetramethylpiperidide (TMP)

“…One ligand prefers the common chair conformation (N1 ligand in Fig. 1), which is adopted in the vast majority of s-block homo-and heterometallic complexes; but, the second TMP ligand adopts a rarer, less thermodynamicallypreferred twisted boat conformation [45] (N2 ligand in Fig. 1).…”

“…[55] Therefore a further potential pathway which could account for the ringopening of TMP − , is that sterically-driven self-deprotonation of the amide takes place, followed by alkene formation, ring opening and reprotonation of the imido N atom [45]] to ascertain whether species akin to 3 can be isolated.…”