Hydrocarbon-soluble, hexaanionic fulleride complexes of magnesium.

Samuel R Lawrence,C André Ohlin,Andreas Stasch,David B Cordes,Alexandra M Z Slawin

doi:10.1039/c9sc03857d

Samuel R Lawrence, C André Ohlin + Show 3 more

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https://doi.org/10.1039/c9sc03857d

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Abstract

The reaction of the magnesium(i) complexes [{(Arnacnac)Mg}2], (Arnacnac = HC(MeCNAr)2, Ar = Dip (2,6-iPr2C6H3), Dep (2,6-Et2C6H3), Mes (2,4,6-Me3C6H2), Xyl (2,6-Me2C6H3)) with fullerene C60 afforded a series of hydrocarbon-soluble fulleride complexes [{(Arnacnac)Mg} n C60], predominantly with n = 6, 4 and 2. 13C{1H} NMR spectroscopic studies show both similarities (n = 6) and differences (n = 4, 2) to previously characterised examples of fulleride complexes and materials with electropositive metal ions. The molecular structures of [{(Arnacnac)Mg} n C60] with n = 6, 4 and 2 can be described as inverse coordination complexes of n [(Arnacnac)Mg]+ ions with C60 n- anions showing predominantly ionic metal-ligand interactions, and include the first well-defined and soluble complexes of the C60 6- ion. Experimental studies show the flexible ionic nature of the {(Arnacnac)Mg}+···C60 6- coordination bonds. DFT calculations on the model complex [{(Menacnac)Mg}6C60] (Menacnac = HC(MeCNMe)2) support the formulation as an ionic complex with a central C60 6- anion and comparable frontier orbitals to C60 6- with a small HOMO-LUMO gap. The reduction of C60 to its hexaanion gives an indication about the reducing strength of dimagnesium(i) complexes.

Highlights

The reaction of the magnesium(I) complexes [{(Arnacnac)Mg}2], (Arnacnac 1⁄4 HC(MeCNAr)2, Ar 1⁄4 Dip (2,6iPr2C6H3), Dep (2,6-Et2C6H3), Mes (2,4,6-Me3C6H2), Xyl (2,6-Me2C6H3)) with fullerene C60 afforded a series of hydrocarbon-soluble fulleride complexes [{(Arnacnac)Mg}nC60], predominantly with n 1⁄4 6, 4 and 2. 13C{1H} NMR spectroscopic studies show both similarities (n 1⁄4 6) and differences (n 1⁄4 4, 2) to previously characterised examples of fulleride complexes and materials with electropositive metal ions
In this work we report on the facile formation of soluble fulleride complexes from reactions of dimeric magnesium(I) compounds LMgMgL with C60
The most accessible dimagnesium(I) compounds are the b-diketiminate complexes [{(Arnacnac)Mg}2] 1, where Arnacnac 1⁄4 HC(MeCNAr)2, and Ar 1⁄4 Dip (2,6-diisopropylphenyl) 1a,26 Dep (2,6-diethylphenyl) 1b,27 Mes 1c,28 and Xyl 1d.1c,4 Treating a partially dissolved mixture of C60 in deuterated benzene with [{(Arnacnac)Mg}2] 1 at room temperature leads in all cases to a change in colour from the characteristic light purple of the fullerene, to dark brown owing to the formation of [{(Arnacnac)

Summary

Introduction

Dimagnesium(I) compounds LMgMgL, where L is a sterically demanding monoanionic ligand, have been employed as soluble, selective, strong, stoichiometric and safe reducing agents towards a range of organic, organometallic and inorganic substrates.1 They have, for example, been employed as reductants to afford compounds with magnesium(I),2 zinc(I) and zinc(0),3 aluminium(I),4 and germanium(0) centres,5 as well as reduced anthracene to its dianion, benzophenone to the ketyl radical,6 reversibly added to the C]C bonds of selected alkenes,7 and a er activation reductively coupled CO.8 they can be regarded as strong to very strong reducing agents,9 the reduction potentials of these reagents have not yet been experimentally determined due to decomposition reactions.1a Reactions of dimagnesium(I) compounds towards substrates with a known series of reduction potentials could give some indication about the reducing strength of these complexes.Buckminsterfullerene, C60, shows ve degenerate orbitals at the HOMO level of hu symmetry, and three degenerate orbitalsEdge Article spin state.13,16 The M3C60 class materials have received considerable attention because some phases with M 1⁄4 K, Rb, Cs are superconductors.16,17 Other fulleride materials with s-block metal ions can show structures with C–C bonded polymeric. 13C{1H} NMR spectroscopic studies show both similarities (n 1⁄4 6) and differences (n 1⁄4 4, 2) to previously characterised examples of fulleride complexes and materials with electropositive metal ions.

Results

Conclusion