Some t-butylmagnesium and related complexes. Reactions between hydrides and organomagnesium compounds

Abstract

Solutions of di-t-butylmagnesium have been prepared by the dioxan precipitation method, and from them several dibutylmagnesium complexes have been obtained. These include But,Mg-dioxan, which is insoluble in toluene and soluble in ether, the bistetrahydrofuran complex which is partly dissociated in benzene, and the tetramethylethylenediamine complex. Reaction between trimethylethylenediamine and Pr' ,Mg and But,Mg gives (Pr'MgNMeC,H,NMe,), and (ButMgNMeC,H,NMe,),, the latter being slightly dissociated in benzene. Pyrolysis of these compounds leads to alkane, not alkene, evolution.Reactions between diethylmagnesium and alkali-metal hydrides either do not take place or result in attack on the solvent. Butyl-lithium gives LiBu"Me,Mg,OEt, on reaction with dimethylmagnesium in ether, but pyrolysis of this gives dimethylmagnesium and lithium hydride. Exchange reactions between sodium trialkylborohydrides and some alkylmagnesium compounds result in the precipitation of magnesium hydride containing occluded alkyl groups.The solid Grignard reagent, (ButMgCIOEt,),, is dimeric in benzene, and is believed to contain chlorine bridges.WHEREAS t-butylmagnesium chloride is a well known and much used Grignard reagent, nothing has been reported concerning di-t-butylmagnesium or its derivatives. The application of the dioxan precipitation method to the preparation of solvent-free di-isopropylmagnesium has been described by Strohmeier and Seifert who pointed out that a temperature of 115" must not be exceeded in the process of separating dioxan in vacuo (this being a lower temperature than some other magnesiumalkyls tolerate), and that they were unable to prepare di-isobutylmagnesium by this method on account of pyrolysis of the product. Though we did not obtain solvent-free di-t-butylmagnesium, on account of the ease with which it loses isobutene when heated, we were able to prepare solutions of it which served as a suitable source for several derivatives. The dioxan precipitation method suffers from two complications when applied to solutions of t-butylmagnesium chloride. Unlike the precipitated dioxan-magnesium bromide complex obtained from, for example, dioxan and methyl-or ethyl-magnesium bromide, the dioxanmagnesium chloride complex from Bu'MgCl does not settle readily and is difficult to remove by filtration, though it could be separated with a centrifuge. Secondly, we found that chloride and dioxan could both be present in solution at the same time, though in low concentration. This is in contrast to the precipitation of dioxan-magnesium bromide, which is virtually complete when the dioxan : total halide ratio exceeds unity. Though chloride can be removed from solution by addition of an excess of dioxan, this was undesirable for our purposes since the presence of dioxan in the resulting solution of di-t-butylmagnesium would have complicated the preparation of several of the other coordination complexes. We therefore added only one mole of dioxan for each mole of chloride, and used, for preparative purposes, ether solutions o...

Terminal beryllium–hydrogen bonding in dimeric (2-dimethylamino-N-methylethylamido)hydridoberyllium, [Be2(C5H13N2)2H2]

“…Compounds of the type RMN(Me)C2H4NMe 2 (R = alkyl) have been reported for M = Be (Coates & Green, 1962;Coates & Roberts, 1968), Mg (Coates & Heslop, 1968) and Zn (Coates & Ridley, 1965). All are dimeric in benzene solution and doubtless have structures similar to that found for [MeMgN(Me)C2HaNMe2] 2 (Magnuson & Stucky, 1969).…”

Deprotonierende Metallierungen mit 'at‐Verbindungen: Synergie, Synthese und Strukturaufbau

“…Richey [11,16] Mischen von Organolithiumverbindungen und Magnesiumhalogeniden im Verhältnis 3:1 oder 4:1 [17] und Reduktion von Dialkylmagnesium mit Lithiumverbindungen [18] -, dennoch blieben die Anwendungen von Magnesiumreagentien in der Synthese bis vor kurzem weitgehend unerforscht. [19] Oshima und Mitarbeiter berichteten 2000 über den effizienten Einsatz von Lithiumtriorganomagnesiaten in Halogen-Metall-Austauschreaktionen.…”

Titanium–Alkaline Earth Molecular Oxides as Supports for Carbanions Derived from μ3‐Ethylidyne Groups

“…[1] [MgR 2 (thf) 2 ] (R = CH 2 Ph, [17] CMe 3 [18] ), [Ba(CH 2 Ph) 2 ], [19] and [M{N(SiMe 3 ) 2 } 2 (thf) 2 ], (M = Mg, [20] Ca, [21] Sr, [21] Ba [21] ) were prepared following the literature methods. Pentamethylcyclopentadiene was purchased from Aldrich and Ph 3 COH from Fluka and sublimed before use.…”