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Cite this: Dalton Trans., 2018, 47,12546

Received 18th April 2018,Accepted 15th May 2018

DOI: 10.1039/c8dt01542b

rsc.li/dalton

Dimethylmagnesium revisited†

Christoph Stuhl and Reiner Anwander *

A compilation of solvent-free homometallic methyl compounds of the type MMex (x = 1–6) is provided

and categorised according to their method of characterisation (powder or single crystal X-ray diffraction,

gas electron diffraction (GED), reactivity, unconfirmed). Recrystallisation of polymeric [MgMe2]n from excess

GaMe3 led to the formation of highly pure [MgMe2]n suitable for single crystal X-ray crystallographic studies.

Transient Mg(GaMe4)2 could be detected in excess GaMe3 by NMR spectroscopy, but its isolation as

Mg(GaMe4)2 failed. On one occasion tetrameric [Mg(GaMe4)(OMe)]4 could be isolated as a minor co-

product. The formation of single-crystalline [MgMe2]n from a saturated ethereal solution could be repro-

duced as reported earlier by Coates et al. Assessing the reactivity of potassium methoxide methanol adduct

toward Mg(AlMe4)2, the protonolysis reaction with MeOH gave unprecedented [Mg(AlMe4){Al(OMe)2Me2}]2featuring one 8-membered [MgOAlO]2 metalloxane ring and two 4-membered metallacycles.

Introduction

Homoleptic metal methyl complexes are regarded as archety-pal organometallics par excellence. It was, in particular,Frankland’s discovery of dimethyl mercury in 18641 which trig-gered immense research efforts to identity such metal methylderivatives across the entire periodic table,‡ as represented byLiMe (s-block),3 WMe6 (d-block),4 AlMe3 (p-block)5 or HoMe3(f-block).6 The fundamental understanding of the M–C(CH3)bonding (ionic versus covalent) has a major impact on aca-demic research and industrial processes alike.7–14 The metalmethyl compounds MMex (x = 1–6), which were isolated andunequivocally structurally characterised by X-ray diffraction,are compiled in Fig. 1 and can be extrapolated to sixpowder15–21 and 19 single-crystal studies.§,4,5,22–41 Moreover,the molecular structure of 13 volatile metal alkyls was revealedby gas electron diffraction (GED).¶,40,42–50 Entries of MMexspecies with associated reactivity studies1,6,25,51–54 and uncon-firmed existence55–64 are also included in Fig. 1. In the mid-20th century, the first single-crystal X-ray structure of a per-methylated donor solvent-free compound, namely dimethylberyllium, was reported.22 However, the characterisation ofhomoleptic metal methyl complexes via single-crystal X-ray

diffraction has remained challenging. In particular the poly-meric s-block compounds still remain elusive due to reactivityand solubility issues. Previous studies from our laboratory onrare-earth and alkaline-earth metal methyl complexes led tothe isolation of X-ray amorphous [LnMe3]n (Ln = Y, Ho, Lu)6,51

and [CaMe2]n, respectively.52 The atomic arrangement of the

lighter homologue [MgMe2]n, which is isostructural to theberyllium congener, was studied by Weiss in 1964 via powderX-ray diffraction experiments.21 Single-crystalline [MgMe2]nobtained from a saturated ethereal solution has been reportedearlier, but unfortunately not examined in detail.65 It was thislatter work by Coates et al., which encouraged us to revisit[MgMe2]n for a more elaborate investigation of its formationand reactivity.

Results and discussionSynthesis and characterisation of single-crystalline [MgMe2]n

[MgMe2]n (1) was prepared following standard procedures froman ethereal [MeMgBr] “Grignard” solution via addition ofdioxane and separation of co-product MgBr2(dioxane).

66–68

Treatment of donor solvent-free 1 with two equiv. AlMe3 gaveMg(AlMe4)2,

69 in analogy to rare-earth metal alkyls “in disguise”of the type Ln(AlMe4)3, which have been studied extensively.70

It is important to note that the addition of the heaviergroup 3 homologue GaMe3 to [LnMe3]n gave homolepticLn(GaMe4)3.

6,71 Accordingly, polymeric [MgMe2]n was treatedwith excess trimethylgallium aiming at putative Mg(GaMe4)2 (2)(Scheme 1). Previous studies in our group have revealed that[MgMe2]n readily dissolves in neat GaMe3,

72 but the formationof Mg(GaMe4)2 could not be unequivocally proven.

†Electronic supplementary information (ESI) available: NMR and crystallo-graphic data. CCDC 1837386–1837388. For ESI and crystallographic data in CIFor other electronic format see DOI: 10.1039/c8dt01542b

Institut für Anorganische Chemie, Eberhard Karls Universität Tübingen (EKUT),

Auf der Morgenstelle 18, 72076, Germany. E-mail: reiner.anwander@uni-tuebingen.de

‡ZnMe2 was earlier reported in 1849,2 but the preparation of HgMe2 wasdescribed in more detail.§Secondary metal⋯CH3 interactions in the solid state.¶B. Beagley, A. G. Robiette and G. M. Sheldrick, unpublished work, 1967.

12546 | Dalton Trans., 2018, 47, 12546–12552 This journal is © The Royal Society of Chemistry 2018

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Heating a clear solution of 1 in neat GaMe3 at 100 °C in apressure tube afforded a small amount of clear colourless crys-tals of 3 (vide supra), upon cooling to ambient temperature.

Separation of the supernatant and evaporation of excessGaMe3 (bp. 56 °C) afforded block-like single crystals of 1*(Fig. 2).

Fig. 1 Overview of homoleptic solvent-free metal methyls MMex. Compounds shown in italics are unconfirmed.

Dalton Transactions Paper

This journal is © The Royal Society of Chemistry 2018 Dalton Trans., 2018, 47, 12546–12552 | 12547

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X-ray structure analysis revealed the molecular structure ofdonor solvent-free [MgMe2]n (1*) (orthorhombic, Ibam) (Fig. 2).Each magnesium in 1* is coordinated by four methyl carbonatoms in a tetrahedral fashion. The Mg–C(CH3) bond length of2.234(2) Å and the interatomic Mg⋯Mg distance of 2.7162(4) Åare in accordance with the metrical parameters determined byWeiss (Mg1–C1 2.24(3) Å, Mg1⋯Mg1 2.72(2) Å).21 The H⋯Hinteratomic distances found between two individual polymerstrands are >3 Å. The 1H NMR spectrum of 1* in thf-d8 atambient temperature revealed one sharp singlet for the mag-nesium methyl groups at −1.79 ppm, indicating high methylgroup mobility when assuming that the polymeric networkconverted into dimeric species [MgMe(µ-Me)(thf)]2.∥72–77 Asolution of 1 in diethyl ether was allowed to evaporate over aperiod of 2 h under ambient conditions and resulted in clearcolourless plate-like crystals of 1* (Scheme 1), confirming theprevious findings by Coates et al.65

Adopting the synthesis strategy by Dietrich et al. establishedfor the conversion of [LnMe3]n into Ln(GaMe4)3,

6 dimethyl-magnesium was reacted with neat GaMe3 in order to isolateputative Mg(GaMe4)2 (2). Combining both metal methyl com-pounds at ambient temperature resulted in a clear solutionwhich was examined by NMR spectroscopy. In order to avoidany reactions with deuterated NMR solvents and formation ofside products, an internal standard of dmso-d6/ethylene glycol

(20 : 80) in a sealed glass ampoule was inserted into a J. Youngvalve NMR tube. The 1H and 13C{1H} NMR spectra revealedthe Mg/Ga–CH3 groups of labile 2 to resonate at −0.22 and2.2 ppm, respectively (see Fig. S3–S5†). Unfortunately, the crys-tallisation of 2 was impeded by the low boiling point of GaMe3(bp. 56 °C) and the high tendency of [MgMe2]n to crystalliseunder these very conditions.

Another attempt at recrystallizing 1 from GaMe3 yielded asmall crop of colourless crystals, which were identified asheteroleptic species [Mg(GaMe4)(OMe)]4 (3). Apparently, smalltraces of adventitious oxygen led to a partial oxidation of[MgMe2]n, while preparing [MgMe2(dioxane)]n at a Schlenkline. Tetrameric 3 (tetragonal, I41/a) has a cuboid arrangementwith magnesium and oxygen atoms at alternating apices. Eachmagnesium centre adopts a distorted octahedral geometry andis surrounded by one η3-coordinated [GaMe4] unit. TheMg1–O1 bond lengths of 2.066(2) to 2.0746(9) Å match thosefound in [Mg4(mhp)4(MeO)4(MeOH)8] (mhp = 6-methylpridine)(2.066(2)–2.095(2) Å), featuring an identical Mg4O4 corestructure (Fig. 3).78

With complex 3 structurally authenticated, we probed thegeneral accessibility of heteroleptic magnesium alkylalumi-nate–alkoxide species. Synthesis protocols applying the reac-tion of MgR2 with stoichiometric amounts of ROH79 or potass-ium alkoxide80 have been reported earlier. Accordingly, thereaction of Mg(AlMe4)2 with substoichiometric amountsof KOMe·MeOH in toluene gave complex [Mg(AlMe4)2{Al(OMe)2Me2}]2 (4, Scheme 2). For comparison, the reactionof Mg(AlMe4)2 with KOMe afforded only traces of methoxyligands detectable by 1H NMR spectroscopy, suggesting proto-nolysis as the dominant reaction pathway. Applying >1 equiv.KOMe·MeOH led to the formation of intricate product mix-tures. Since bimetallic Mg[Al(OiPr)4]2 and Mg[Al(OtBu)4]2 were

Fig. 2 Pentameric section of the polymeric solid-state structure of[MgMe2]n (1*). Atomic displacement ellipsoids are shown at 50% prob-ability. Selected bond lengths (Å) and angles (°) for 1*: Mg1–C1 2.234(2),Mg1⋯Mg1’ 2.7162(4), C1–H1 0.92(3), C1–H2 0.82(2); Mg1–C1–Mg1’ 74.88(4),C1–Mg1–C1’ 110.23(7), Mg1–C1–H1 109.2(14), Mg1–C1–H2 84.7(12).

Scheme 1 Quantitative access to single-crystalline [MgMe2]n (1*) viarecrystallisation from GaMe3 or by evaporation of a saturated etherealsolution.

Fig. 3 Molecular structure of [Mg(GaMe4)(OMe)]4 (3, left) and drawingof the molecular Mg4O4 core structure (right). Atomic displacementellipsoids are shown at 50% probability. Selected bond lengths (Å) andangles (°) for 3: Mg1–C2 2.455(2), Mg1–C3 2.667(3), Mg1–C4 2.604(3),Mg1–O1 2.072(2), Ga1–C2 2.073(2), Ga1–C3 2.037(2), Ga1–C4 2.049(2),Ga1–C5 1.959(2), O1–C1 1.446(2), O1–Mg1–O1’ 83.28(4) O1–Mg1–O1’’83.07(4), O1’–Mg–O1’’ 82.54(5), Ga1–C2–Mg1 69.17(4), Ga1–C3–Mg165.21(6), Ga1–C4–Mg1 66.43(5), C2–Ga1–C3 103.90(9), C2–Ga1–C4104.69(7), C3–Ga1–C4 106.04(7) C2–Ga1–C5 111.78(8), C3–Ga1–C5114.59(8), C4–Ga1–C5 114.79(8).

∥Further known dimethylmagnesium complexes supported by Lewis bases avail-able in the CSD database: [{MgMe2(thf )}2(μ-dabco)] (dabco = 1,4-diazabicyclo[2.2.2]octane),73 [{MgMe2(thf)}(pmdta)] (pmdta = N,N,N′,N″,N″-pentamethyldi-ethylenetriamine),73,74 [MgMe2(tmeda)]2 (tmeda = N,N,N′,N′-tetramethyl-ethylenediamine),75 [MgMe2(quinuclidine)] (quinuclidine = 1-azabicyclo[2.2.2]octane),76 [MgMe2(Me6tren)] (Me6tren = tris(2-dimethylaminoethyl)amine).77

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already described,81,82 compounds such as mixed-ligandMg[Al(OMe)xMe4−x] or homoleptic Mg[Al(OMe)4]2 might befeasible (Scheme 2).

Concentrating the toluene solution of crude 4 and frac-tional crystallisation led to the isolation of two specieswith different crystal morphologies, dimeric [Mg(AlMe4){Al(OMe)2Me2}]2 (4) and unreacted Mg(AlMe4)2. The molecularstructure of 4 features a central 8-membered [MgOAlO]2 metal-oxane ring which is flanked by two 4-membered [MgCAlC]metallacycles. The four-coordinate magnesium centres in 4(monoclinic, P21/n) display symmetrically arranged methyl andmethoxy ligands (Fig. 4). The Mg–O1 and Al2–O1 bond lengthsin 4 of 1.938(2) Å and 1.811(2) Å, respectively, are slightlyshorter than those in polymeric [Mg{Al(OMe)2Me2}2(dioxane)]n(Mg–O1 2.05(1) Å, Al2–O1 1.80(2) Å).83 Not surprisingly, theinteratomic Mg⋯Al distance of 3.304(2) Å in κ1-coordinated[Al(OMe2)Me2] is significantly longer than in the η2-coordinatedunit (Mg⋯Al 2.93(1) Å).

The 1H NMR spectrum of 4 in benzene-d6 at ambient tem-perature displays four dominant singlets each for the methoxy(δ 3.28, 3.05, 3.04 and 3.01 ppm) and methyl groups (δ −0.43,−0.49, −0.63 and −0.73 ppm), with an overall integral ratio of1 : 3 (Fig. S6 and S7†). A variable temperature (VT) 1H NMRspectroscopic study of 4 in toluene-d8 revealed enhanced flux-

ionality at elevated temperature as indicated by two broadsignals each for the methoxy (δ 3.33, 3.17 ppm) and methylgroups at 80 °C (δ −0.58, −0.72 ppm), but retaining the com-bined integral ratio of 1 : 3 (Fig. S8 and S9†). Cooling thesample to −80 °C resulted in extensive signal splitting and verycomplicated signal patterns. This might originate from abroad variety of possible bridging and terminal positions forboth ligands. This phenomenon for bimetallic magnesiumaluminium species was also observed in Mg[Al(OiPr)4]2.

81 Forcomplex 4 such a fluxionality might involve exchange pro-cesses like Schlenk equilibria and redistribution of the hetero-aluminate ligands. These assumptions were further supportedby the 1H NOESY NMR spectra of 4, revealing the expectedclose contacts between methyl and methoxy ligands andassociated exchange processes (Fig. S10/S11†).

Conclusions

Encouraged by a compilation of already synthesised andcharacterised homoleptic metal methyl complexes, we havesuccessfully pursued the fabrication of single-crystalline[MgMe2]n. The formation of such [MgMe2]n of high purity wasachieved via crystallisation from trimethylgallium involvingtransient Mg(GaMe4)2. The reported single crystal X-ray data of[MgMe2]n are only the second for an s-block metal methyl (cf.,isostructural [BeMe2]n), while the structure parameters are inaccordance with those previously determined by powder X-raydiffraction.21 Attempts at isolating putative Mg(GaMe4)2 led tothe isolation of tetrameric [Mg(GaMe4)(OMe)]4 (through thepresence of adventitious oxygen), representing the first mag-nesium complex coordinated by the GaMe4 moiety. Althoughobtained serendipitously, the octametallic cluster points outthe stabilising effect of alkoxy ligands on Mg–GaMe4 bonding,thus paving the way for further investigations of this class ofbimetallic compounds. The targeted synthesis of such mixedmagnesium alkyl alkoxide species by treating methylaluminateMg(AlMe4)2 with substoichiometric amounts of MeOH gavedimeric [Mg(AlMe4){Al(OMe)2Me2}]2, which revealed an intri-cate dynamic behaviour in solution.

ExperimentalCrystallography and crystal structure determination

Single crystals were grown using standard techniques fromsaturated solutions (1, GaMe3/diethyl ether; 3, neat GaMe3; 4,toluene). When 1 was heated in neat GaMe3 single crystals of 3formed at 50 °C. Single crystals suitable for X-ray structure ana-lysis were selected in a glovebox and coated with Parabar10 312 (previously known as Paratone N, Hampton Research)and fixed on a nylon loop/glass fibre. Crystallographic data forcompounds 1, 3 and 4 were collected on a Bruker APEX DUOinstrument equipped with an IμS microfocus sealed tube andQUAZAR optics for MoKα radiation (λ = 0.71073 Å). The datacollection strategy was determined using COSMO84 employing

Scheme 2 Synthesis protocol for [Mg(AlMe4){Al(OMe)2Me2}]2 (4, top)and Schlenk equilibrium between 4 and homoleptic Mg(AlMe4)2 andMg[Al(OMe)4]2 (bottom).

Fig. 4 Molecular structure of [Mg(AlMe4){Al(OMe)2Me2}]2 (4). Atomicdisplacement ellipsoids are shown at 50% probability. Selected bondlengths (Å) and angles (°) for 4: Mg1–C1 2.246(4), Mg1–C2 2.249(4),Mg1–O1 1.938(2), Mg1–O2’ 1.943(2), Al1–C1 2.080(4), Al1–C2 2.080(4),Al1–C3 1.969(4), Al1–C4 1.961(4), Al1–Mg1 2.691(2), Al2–C6 1.961(3),Al2–C7 1.973(3), Al2–O1 1.811(2), Al2–O2 1.817(2); Al1–C1–Mg1 76.8(2),Al1–C2–Mg2 76.8(2) Mg1–O1–Al2 123.6(2), C1–Al1–C2 107.7(2), C1–Al1–C3 107.2(2), C1–Al1–C4 107.7(2), C2–Al1–C3 109.2(2), C2–Al1–C4105.9(2).

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ω- and ϕ scans. Raw data were processed using APEX85 andSAINT,86 corrections for absorption effects were applied usingSADABS.87 The structures were solved by direct methods andrefined against all data by full-matrix least-squares methodson F2 using SHELXTL88 and Shelxle.89 Both hydrogen atoms of1 were located by difference Fourier synthesis and refined iso-tropically with no further restraints. The occupancy of H(2) in1 was set to 10.5 due to its special position. All graphics wereproduced employing ORTEP-390 and POV-Ray.91 Furtherdetails of the refinement and crystallographic data are listed inTable S1† and in the CIF files. CCDCs 1837386 (1), 1837387 (3)and 1837388 (4)† contain all the supplementary crystallo-graphic data for this paper.

General experimental procedures and instrumentation

All manipulations were performed in a glovebox (MBraun200B; <0.1 ppm O2, <0.1 ppm H2O) or by using Schlenk tech-niques under an argon atmosphere and in oven-dried glass-ware. Solvents (THF, n-hexane and toluene) were purified viaGrubbs columns (MBraun SPS, solvent purification system),and stored inside a glovebox. Methanol (99.98%), methyl-magnesium bromide (3.0 M in Et2O) and potassium metalwere purchased from Sigma Aldrich and used as received.GaMe3 (Dockweiler Chemicals, optoelectronic grade) wasused as received. KOMe,92 KOMe·MeOH,92 [MgMe2]n (1)68 andMg(AlMe4)2

69 were synthesised according to literature pro-cedures. 1,4-Dioxane was dried over sodium metal, distilledand degassed prior to use. Benzene-d6 and thf-d8 were pur-chased from Eurisotop, dried over NaK alloy for two days andfiltered (benzene-d6) or distilled off (thf-d8) prior to use.1H NMR and 13C{1H} NMR spectra were recorded on a BrukerAVII + 400 (1H: 400.13 MHz; 13C: 125.76 MHz) spectrometer at299 K. 1H NMR spectra of Mg(GaMe4)2 were recorded by usinga J. Young valve NMR tube at variable temperatures on aBruker AVII + 500 instrument (1H: 500.13 MHz; 13C:125.76 MHz). Infrared spectra were recorded on a Nicolet 6700FTIR spectrometer (ν̃ = 4000–600 cm−1) using a DRIFTchamber with dry KBr/sample mixtures. Elemental analyseswere performed on an Elementar Vario MICRO cube.

Preparation and characterisation of compounds 1–3

[MgMe2]n (1*). Method (a): Fully desolvated [MgMe2]n(100 mg, 1.84 mmol) was dissolved in 2 mL diethyl ether atambient temperature. The solution was slowly evaporated for2 h at ambient temperature under inert atmospheres to affordcolourless single crystals of 1* (98.8 mg, 1.82 mmol, 99%) suit-able for X-ray structure analysis. The amount of residual Et2Owas determined by 1H NMR spectroscopy and verified bymicroanalysis. 1H NMR (400 MHz, THF-d8, 26 °C): δ = −1.79 (s,6 H, Mg–CH3) ppm. 13C{1H} NMR (126 MHz, THF-d8, 26 °C):δ = −17.0 (Mg–CH3) ppm. DRIFT (KBr): 2868s, 2830m, 2791m,1205s, 1190s, 609s, 596s, 443s, 431s cm−1. Elemental analysiscalcd (%) for C2H6Mg (54.38 g mol−1): C 44.18, H 11.12;Found: C 44.92, H 11.12.

Method (b): [MgMe2]n (100 mg, 1.84 mmol) of high purity(handled in a glovebox, residual solvent evaporated under high

vacuum prior to use) was dissolved in neat GaMe3 (700 mg,6.10 mmol). Fast evaporation of GaMe3 at ambient conditionsin a glovebox led to formation of single-crystalline 1*.

Mg(GaMe4)2 (2). [MgMe2]n (50.0 mg, 920 μmol) of highpurity was dissolved in neat GaMe3 (500 μL, 8.07 mmol) andtransferred into a J. Young valve NMR tube with an internalstandard (dmso-d6/ethylene glycol 20 : 80). 1H NMR (400 MHz,dmso-d6, 26 °C): δ = −0.22 (s, 24 H, Mg–CH3/Ga–CH3) ppm.13C NMR (126 MHz, dmso-d6, 26 °C): δ = 2.2 (Mg–CH3/Ga–CH3) ppm. Attempts to crystallise 2 were hampered by the lowboiling point of GaMe3 (bp. 56 °C) and the high tendency of[MgMe2]n to crytallise under these conditions.

[Mg(GaMe4)(OMe)]4 (3). Method (a): Residual etherealsolvent in [MgMe2]n (100 mg, 1.84 mmol) was evaporatedunder high vacuum until dry, while adventitious oxygen waspresent. The white solid was dissolved in neat GaMe3 (700 mg,6.10 mmol) and heated to 100 °C for 3 h in a pressure tube. Asmall crop of clear colourless single crystals of 3 suitable forX-ray diffraction analysis had formed when the reactionmixture was chilled to ambient temperature (3, minorproduct).

Method (b): Residual ethereal solvent in [MgMe2] (45.0 mg,828 μmol) was evaporated under high vacuum until dry, whileadventitious oxygen was present. The white solid was dissolvedin neat GaMe3 (285 mg, 2.48 mmol) and sealed in a glassampoule. Same observations have been made as withmethod (a). Fast evaporation of GaMe3 under ambient con-ditions in a glovebox led to formation of a second crystallinespecies (1*, major product). Single crystal X-ray diffractionanalysis revealed the formation of 1*.

[Mg(AlMe4){Al(OMe)2Me2}]2 (4). To a solution of Mg(AlMe4)2(182 mg, 920 μmol) dissolved in 2 mL toluene solidKOMe·MeOH (129 mg) (elemental analysis calcd (%) forKOCH3·MeOH (102.17 g mol−1): C: 23.51, H 6.91; Found: C20.16, H 5.49) was added. Instant gas evolution was observed.The reaction mixture was stirred for 2 h and then the toluenesolution was separated from solid KOMe by filtration. Afterevaporation of the volatiles, 4 was obtained as clear colourlesscrystals (72.3 mg, 314 μmol, 34%). Prolonged drying resultedin loss of product. Using fully desolated KOMe (elemental ana-lysis calcd (%) for KOCH3 (70.13 g mol−1): C: 17.13, H 4.13;Found: C 16.97, H 4.22) for the synthesis only small traces ofproduct were detected via 1H NMR spectroscopy. 1H NMR(400 MHz, benzene-d6, 26 °C): δ = 3.28/3.05/3.04/3.01 (4xs,12H, Mg–OCH3, Al–OCH3), −0.43/−0.49/−0.63/−0.73 (4xs, 36H, Mg–CH3, Al–CH3) ppm. 13C NMR (126 MHz, benzene-d6,26 °C): δ = 51.9/51.2/50.9/50.3 (Mg–OCH3, Al–OCH3),−7.5/−8.5/−9.4/−11.1 (Mg–CH3, Al–CH3) ppm. Elemental ana-lysis calcd (%) for C8H24MgAl2O2 (230.55 g mol−1): C: 41.68,H 10.49; Found: C 41.57, H 10.48.

Conflicts of interest

There are no conflicts of interest.

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Acknowledgements

We are grateful to the German Science Foundation DFG forgenerous support (Grant AN 238/15-2). We thank to Dr KlausEichele and Kristina Strohmeier for supporting NMR spectro-scopic measurements.

Notes and references

1 E. Frankland and B. F. Duppa, Liebigs Ann. Chem., 1864,130, 104–117.

2 E. Frankland, Liebigs Ann. Chem., 1849, 71, 213–216.3 W. Schlenk and J. Holtz, Ber. Dtsch. Chem. Ges., 1917, 50,

262–274.4 V. Pfennig and K. Seppelt, Science, 1996, 271, 626–628.5 R. G. Vranka and E. L. Amma, J. Am. Chem. Soc., 1967, 89,

3121–3126.6 H. M. Dietrich, G. Raudaschl-Sieber and R. Anwander,

Angew. Chem., Int. Ed., 2005, 44, 5303–5306.7 J. Campos, J. López-Serrano, R. Peloso and E. Carmona,

Chem. – Eur. J., 2016, 22, 6432–6457.8 M. Bochmann, Organometallics and catalysis: an introduc-

tion, Oxford University Press, USA, 2015.9 R. H. Crabtree, The organometallic chemistry of the transition

metals, John Wiley & Sons, 2009.10 M. Schlosser, Organometallics in synthesis: third manual,

John Wiley & Sons, 2013.11 S. Alexander Jacob and K. Ruhlandt-Senge, Eur. J. Inorg.

Chem., 2002, 2002, 2761–2774.12 W. D. Buchanan, D. G. Allis and K. Ruhlandt-Senge, Chem.

Commun., 2010, 46, 4449–4465.13 M. Westerhausen, Angew. Chem., Int. Ed., 2001, 40, 2975–

2977.14 M. Westerhausen, A. Koch, H. Görls and S. Krieck, Chem. –

Eur. J., 2017, 23, 1456–1483.15 E. Weiss and E. A. C. Lucken, J. Organomet. Chem., 1964, 2,

197–205.16 E. Weiss and G. Hencken, J. Organomet. Chem., 1970, 21,

265–268.17 E. Weiss, G. Sauermann and G. Thirase, Chem. Ber., 1983,

116, 74–85.18 E. Weis and G. Sauermann, Chem. Ber., 1970, 103, 265–271.19 E. Weiss and G. Sauermann, Angew. Chem., 1968, 80, 123–124.20 E. Weiss and H. Köster, Chem. Ber., 1977, 110, 717–720.21 E. Weiss, J. Organomet. Chem., 1964, 2, 314–321.22 A. I. Snow and R. E. Rundle, Acta Crystallogr., 1951, 4, 348–352.23 B. Roessler, S. Kleinhenz and K. Seppelt, Chem. Commun.,

2000, 1039–1040.24 B. Roessler and K. Seppelt, Angew. Chem., Int. Ed., 2000, 39,

1259–1261.25 R. R. Schrock and P. Meakin, J. Am. Chem. Soc., 1974, 96,

5288–5290.26 J. Bacsa, F. Hanke, S. Hindley, R. Odedra, G. R. Darling,

A. C. Jones and A. Steiner, Angew. Chem., Int. Ed., 2011, 50,11685–11687.

27 F. Hanke, S. Hindley, A. C. Jones and A. Steiner, Chem.Commun., 2016, 52, 10144–10146.

28 S. K. Byram, J. K. Fawcett, S. C. Nyburg and R. J. O’Brien,J. Chem. Soc. D, 1970, 16–17.

29 H.-G. Stammler, S. Blomeyer, R. J. F. Berger andN. W. Mitzel, Angew. Chem., Int. Ed., 2015, 54, 13816–13820.

30 N. W. Mitzel, C. Lustig, R. J. F. Berger and N. Runeberg,Angew. Chem., Int. Ed., 2002, 41, 2519–2522.

31 E. L. Amma and R. E. Rundle, J. Am. Chem. Soc., 1958, 80,4141–4145.

32 A. J. Blake and S. Cradock, J. Chem. Soc., Dalton Trans.,1990, 2393–2396.

33 G. M. Sheldrick and W. S. Sheldrick, J. Chem. Soc. A, 1970,28–30.

34 B. Krebs, G. Henkel and M. Dartmann, Acta Crystallogr.,1989, 45, 1010–1012.

35 H. Fleischer, S. Parsons and C. R. Pulham, Acta Crystallogr.,2003, 59, m11–m13.

36 S. Wallenhauer and K. Seppelt, Inorg. Chem., 1995, 34, 116–119.

37 S. Schulz, A. Kuczkowski, D. Bläser, C. Wölper, G. Jansenand R. Haack, Organometallics, 2013, 32, 5445–5450.

38 S. Wallenhauer and K. Seppelt, Angew. Chem., Int. Ed. Engl.,1994, 33, 976–978.

39 P. H. Lewis and R. E. Rundle, J. Chem. Phys., 1953, 21, 986–992.

40 A. J. Blake, C. R. Pulham, T. M. Greene, A. J. Downs,A. Haaland, H. P. Verne, H. V. Volden, C. J. Marsden andB. A. Smart, J. Am. Chem. Soc., 1994, 116, 6043–6044.

41 J. Lewiński, J. Zachara, K. B. Starowieyski, I. Justyniak,J. Lipkowski, W. Bury, P. Kruk and R. Woźniak,Organometallics, 2005, 24, 4832–4837.

42 A. Haaland, A. Hammel, K. Rypdal, H. P. Verne,H. V. Volden and C. Pulham, Angew. Chem., Int. Ed. Engl.,1992, 31, 1464–1467.

43 H. T. Almenningen, A. Haaland and S. Samdal, Acta Chem.Scand., Ser. A, 1982, 36, 159–166.

44 H. A. Blom and R. Seip, Acta Chem. Scand., Ser. A, 1983, 37,1983.

45 A. Haaland, H. P. Verne, H. V. Volden and J. A. Morrison,J. Am. Chem. Soc., 1995, 117, 7554–7555.

46 B. Beagley and D. G. Schmidling, J. Mol. Struct., 1974, 21,437–444.

47 A. Almenningen, S. Halvorsen and A. Haaland, Acta Chem.Scand., 1971, 25, 1937–1945.

48 L. Pauling and A. W. Laubengayer, J. Am. Chem. Soc., 1941,63, 480–481.

49 M. Nagashima, H. Fujii and M. Kimura, Bull. Chem. Soc.Jpn., 1973, 46, 3708–3711.

50 É. Csákvári, B. Rozsondai and I. Hargittai, J. Mol. Struct.,1991, 245, 349–355.

51 M. Zimmermann, D. Rauschmaier, K. Eichele,K. W. Törnroos and R. Anwander, Chem. Commun., 2010,46, 5346–5348.

52 B. M. Wolf, C. Stuhl, C. Maichle-Mössmer andR. Anwander, J. Am. Chem. Soc., 2018, 140, 2373–2383.

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53 L. M. Dennis and F. E. Hance, J. Phys. Chem., 1925, 30,1055–1059.

54 R. R. Schrock, J. Organomet. Chem., 1976, 122, 209–225.55 D. A. Payne and R. T. Sanderson, J. Am. Chem. Soc., 1958,

80, 5324–5324.56 K. Clauss and C. Beermann, Angew. Chem., 1959, 71,

627.57 R. E. Rundle and J. H. Sturdivant, J. Am. Chem. Soc., 1947,

69, 1561–1567.58 H. Gilman, R. G. Jones and L. A. Woods, J. Org. Chem.,

1952, 17, 1630–1634.59 G. Semerano and L. Riccoboni, Ber. Dtsch. Chem. Ges.,

1941, 74, 1089–1099.60 H. J. Berthold and G. Groh, Angew. Chem., 1966, 78,

495.61 R. Riemschneider, H. G. Kassahn and W. Schneider,

Z. Naturforsch., B: Anorg. Chem. Org. Chem. Biochem. Biophys.Biol., 1960, 15, 547.

62 C. Beermann and K. Clauss, Angew. Chem., 1959, 71,627.

63 W. Mowat, A. J. Shortland, N. J. Hill and G. Wilkinson,J. Chem. Soc., Dalton Trans., 1973, 770–778.

64 H. J. Berthold and G. Groh, Z. Anorg. Allg. Chem., 1963, 319,230–235.

65 G. E. Coates, J. A. Heslop, M. E. Redwood and D. Ridley,J. Chem. Soc. A, 1968, 1118–1125.

66 W. Schlenk and W. Schlenk, Ber. Dtsch. Chem. Ges., 1929,62, 920–924.

67 W. Schlenk, Ber. Dtsch. Chem. Ges., 1931, 64, 734–736.68 A. C. Cope, J. Am. Chem. Soc., 1935, 57, 2238–2240.69 J. L. Atwood and G. D. Stucky, J. Am. Chem. Soc., 1969, 91,

2538–2543.70 M. Zimmermann and R. Anwander, Chem. Rev., 2010, 110,

6194–6259.71 M. Zimmermann, R. Litlabø, K. W. Törnroos and

R. Anwander, Organometallics, 2009, 28, 6646–6649.72 O. Michel, C. Meermann, K. W. Törnroos and R. Anwander,

Organometallics, 2009, 28, 4783–4790.

73 R. I. Yousef, B. Walfort, T. Rüffer, C. Wagner, H. Schmidt,R. Herzog and D. Steinborn, J. Organomet. Chem., 2005,690, 1178–1191.

74 H. Viebrock and E. Weiss, J. Organomet. Chem., 1994, 464,121–126.

75 T. Greiser, J. Kopf, D. Thoennes and E. Weiss, J. Organomet.Chem., 1980, 191, 1–6.

76 J. Toney and G. D. Stucky, J. Organomet. Chem., 1970, 22,241–249.

77 L. M. Guard and N. Hazari, Organometallics, 2013, 32,2787–2794.

78 G. S. Nichol and W. Clegg, Inorg. Chim. Acta, 2006, 359,3474–3480.

79 S. Heitz, Y. Aksu, C. Merschjann and M. Driess, Chem.Mater., 2010, 22, 1376–1385.

80 E. M. Hanawalt, J. Farkas and H. G. Richey,Organometallics, 2004, 23, 416–422.

81 J. A. Meese-Marktscheffel, R. Fukuchi, M. Kido,G. Tachibana, C. M. Jensen and J. W. Gilje, Chem. Mater.,1993, 5, 755–757.

82 S. Mathur, H. Shen, E. Hemmer, T. Ruegamer andC. Holzapfel, MRS Proc., 2011, 848, FF1.10.

83 J. L. Atwood and G. D. Stucky, J. Organomet. Chem., 1968,13, 53–60.

84 COSMO v. 1.61, Bruker AXS Inc., Madison, WI, USA, 2012.85 APEX v. 2012.10_0, Bruker AXS Inc., Madison, WI, USA,

2012.86 SAINT v. 7.99A, Bruker AXS Inc., Madison, WI, USA, 2010.87 G. M. Sheldrick, SADABS v. 2012/1, Bruker AXS Inc.,

Madison, WI, USA, 2012.88 G. M. Sheldrick, SHELXTL v. 2012.10_2, Bruker AXS Inc.,

Madison, WI, USA, 2012.89 C. B. Hübschle, G. M. Sheldrick and B. Dittrich, J. Appl.

Crystallogr., 2011, 44, 1281–1284.90 L. J. Farrugia, J. Appl. Crystallogr., 1997, 30, 565.91 POV-Ray v. 3.6, Persistence of Vision Pty. Ltd., Williamstown,

Victoria, Australia, 2004. http://www.povray.org/.92 E. Weiss, Helv. Chim. Acta, 1963, 46, 2051–2054.

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