Abstract
The chemistry of the Group 13 metals is dominated by the +1 and +3 oxidation states, and simple monomeric M(II) species are typically short-lived, highly reactive species. Here we report the first thermally robust monomeric MX2 radicals of gallium, indium and thallium. By making use of sterically demanding boryl substituents, compounds of the type M(II)(boryl)2 (M = Ga, In, Tl) can be synthesized. These decompose above 130 °C and are amenable to structural characterization in the solid state by X-ray crystallography. Electron paramagnetic resonance and computational studies reveal a dominant metal-centred character for all three radicals (>70% spin density at the metal). M(II) species have been invoked as key short-lived intermediates in well-known electron-transfer processes; consistently, the chemical behaviour of these novel isolated species reveals facile one-electron shuttling processes at the metal centre.
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References
Downs, A. J. & Himmel, H-J. The Group 13 Metals Aluminium, Gallium, Indium and Thallium: Chemical Patterns and Peculiarities (eds Aldridge, S. & Downs, A. J.) Ch. 1 (Wiley, 2011).
Uhl, W. & Layh, M. The Group 13 Metals Aluminium, Gallium, Indium and Thallium: Chemical Patterns and Peculiarities (eds Aldridge, S. & Downs, A. J.) Ch. 4 (Wiley, 2011).
Knight, L. B. Jr, Banisaukas, J. J. III, Babb, R. & Davidson, E. R. Electron spin resonance matrix isolation and ab initio theoretical investigations of 69,71GaH2, 69,71GaD2, H69,71GaCH3, and D69,71GaCD3 . J. Chem. Phys. 105, 6607–6615 (1996).
Kaim, W. & Matheis, W. Bis(1,4-di-tert-butyl-1,4-diazabutadiene)gallium is not a gallium(II) compound. Chem. Commun. 597–598 (1991).
Pardoe, J. A. J. & Downs, A. J. Development of the chemistry of indium in formal oxidation states lower than +3. Chem. Rev. 107, 2–45 (2007).
Khoshtariya, D. E., Dolidze, T. D., Zusman, L., Lindberg, G. & Glaser, J. Two-electron transfer for Tl(aq)3+/Tl(aq)+ revisited. Common virtual [Tl(II)–Tl(II)]4+ intermediate for homogeneous (superexchange) and electrode (sequential) mechanisms. Inorg. Chem. 41, 1728–1738 (2002).
Falcinella, B., Felgate, P. D. & Laurence, G. S. Aqueous chemistry of thallium(II). Part I. Kinetics of reaction of thallium(II) with cobalt(III) and iron(III) ions and oxidation–reduction potentials of thallium(II). J. Chem. Soc., Dalton Trans. 1367–1373 (1974).
Segawa, Y., Yamashita, M. & Nozaki, K. Boryllithium: isolation, characterization, and reactivity as a boryl anion. Science 314, 113–115 (2006).
Saleh, L. M. A. et al. Group 3 and lanthanide boryl compounds: syntheses, structures and bonding analysis of Sc–B, Y–B and Lu–B σ-coordinated NHC analogues. J. Am. Chem. Soc. 133, 3836–3839 (2011).
Protchenko, A. V. et al. A stable two-coordinate acyclic silylene. J. Am. Chem. Soc. 134, 6500–6503 (2012).
Eichler, B. E., Hardman, N. J. & Power, P. P. In 8(C6H3-2,6-Mes2)4 (Mes=C6H2-2,4,6-Me3): a metal-rich main-group cluster with a distorted cubane structure. Angew. Chem. Int. Ed. 39, 383–385 (2000).
Albright, T. A., Burdett, J. K. & Whangbo, M. H. Orbital Interactions in Chemistry 2nd edn (Wiley, 2013).
Cooke, A. H. & Duffus, H. J. The magnetic susceptibility of nitric oxide in a clathrate compound. Proc. Phys. Soc. A 67, 525–527 (1954).
Leininger, T. et al. Spin–orbit interaction in heavy group 13 atoms and TlAr. Chem. Phys. 217, 19–27 (1997).
Power, P. P. Main group elements as transition metals. Nature 463, 171–177 (2010).
Davidson, P. J., Hudson, A., Lappert, M. F. & Lednor, P. W. Tris[bis(trimethylsilyl)methyl]tin(III), R3Sn•: an unusually stable stannyl radical, from photolysis of R2Sn. J. Chem. Soc., Chem. Commun. 829–830 (1973).
Power, P. P. Persistent and stable radicals of the heavier main group elements and related species. Chem. Rev. 103, 789–810 (2003).
Lee, V. Y. & Sekiguchi, A. Stable silyl, germyl, and stannyl cations, radicals, and anions: heavy versions of carbocations, carbon radicals, and carbanions. Acc. Chem. Res. 40, 410–419 (2007).
Rodriguez, A., Prasang, C., Gandon, V., Bourg, J-B. & Bertrand, G. Stable singlet diradicals based on boron and phosphorus. ACS Symp. Ser. 917, 81–93 (2007).
Sprague, E. D. & Williams, F. ESR spectrum of BH3•− in gamma-irradiated tetramethylammonium borohydride. Mol. Phys. 20, 375–378 (1971).
Pluta, C., Pörschke, K-R., Krüger, C. & Hildebrand, K. An Al–Al one-electron π bond. Angew. Chem. Int. Ed. Engl. 32, 388–390 (1993).
He, X. et al. Reduction of a tetraaryldigallane to afford a radical anion with Ga–Ga multiple bonding character. Angew. Chem. Int. Ed. Engl. 32, 717–719 (1993).
Dohmeier, C. et al. [AltBu]6•−: EPR spectroscopic evidence and ab initio calculations. Angew. Chem. Int. Ed. Engl. 32, 1428–1430 (1993).
Wehmschulte, R. J. et al. Reduction of a tetraaryldialane to generate aluminum–aluminum π-bonding. Inorg. Chem. 32, 2983–2984 (1993).
Uhl, W., Vester, A., Kaim, W. & Poppe, J. Dialan-radikalanionen [R2Al–AlR2]•−. J. Organomet. Chem. 454, 9–13 (1993).
Uhl, W., Schütz, U., Kaim, W. & Waldhör, E. Das tetraalkyldigallan-radikalanion [R2Ga–GaR2]•− [R=CH(SiMe3)2] mit langer einelektron-π-bindung. J. Organomet. Chem. 501, 79–85 (1995).
Haaland, A. et al. Gas-phase structure of the monomeric alkylgallium(I) compound Ga[C(SiMe3)3] and the electrochemical behavior of Ga4[C(SiMe3)3]4 and In4[C(SiMe3)3]4 with EPR evidence for a Ga4R4 radical anion. Organometallics 15, 1146–1150 (1996).
Wiberg, N., Amelunxen, K., Nöth, H., Schmidt, M. & Schwenk, H. Tetrasupersilyldiindium (In–In) and tetrasupersilyldithallium (Tl–Tl): (tBu3Si)2M–M(SitBu3)2 (M=In, Tl). Angew. Chem. Int. Ed. Engl. 35, 65–67 (1996).
Uhl, W., Cuypers, L., Kaim, W., Schwederski, B. & Koch, R. [Ga9(CMe3)9]•− – a persistent cluster radical anion, boron-analogous chemistry with the heavier homologue gallium. Angew. Chem. Int. Ed. 42, 2422–2423 (2003).
Uson, R., Fornies, J., Tomas, M., Garde, R. & Alonso, P. J. Synthesis and structure of [nBu4N]2[Tl{Pt(C6F5)4}2], the first paramagnetic compound containing thallium(III). J. Am. Chem. Soc. 117, 1837–1838 (1995).
Nakamoto, M., Yamasaki, T. & Sekiguchi, A. Stable mononuclear radical anions of heavier group 13 elements: [(tBu2MeSi)3E•–][K+(2.2.2-cryptand)] (E=Al, Ga). J. Am. Chem. Soc. 127, 6954–6955 (2005).
Hitchcock, P. B., Huang, Q., Lappert, M. F. & Zhou, M. The coordination chemistry of the C1-symmetric bis(silyl)methyl ligand [CH(SiMe3){SiMe(OMe)2}]− revisited: Li/M- (M=Zn, Tl, Ce), Li4- or Ce2-methoxy-bridged alkyls. Dalton Trans. 2988–2993 (2005).
Acknowledgements
We thank the Leverhulme Trust (F/08699/E), the Oxford University John Fell Fund, the Australian Research Council (DP120101300 and FT120100421) and the Engineering and Physical Sciences Research Council (EPSRC) (EP/F019181/1, EP/F055412/1 and access to the NMSF, Swansea). We are grateful for computational resources from the EPSRC's National Service for Computational Chemistry Software, http://www.nsccs.ac.uk), and also thank the University College London's High Performance Computing Facility (Legion@UCL) and associated support services, and the e-Infrastructure South consortium's Centre for Innovation for computing resources via its ‘Iridis’ facility.
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A.V.P. and D.D. synthesized and characterized the compounds. J.R.H. carried out the EPR studies. C.Y.T., A.D.S., M.J.K., N.P. and C.J. mounted the crystals, collected the single-crystal X-ray crystallographic data and solved the crystal structures. K.H.B. and N.K. carried out the DFT calculations. R.T. carried out the electrochemical measurements. N.K., P.M., C.J. and S.A. generated and managed the project and wrote the manuscript. All authors discussed the results and commented on the manuscript.
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Supplementary information
Supplementary information
Supplementary information (PDF 6896 kb)
Supplementary information
Crystallographic data for compound 2-Ga. (CIF 24 kb)
Supplementary information
Crystallographic data for compound 2-In. (CIF 22 kb)
Supplementary information
Crystallographic data for compound 2-Tl. (CIF 22 kb)
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Crystallographic data for compound 3-Ga. (CIF 38 kb)
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Crystallographic data for compound 3-In. (CIF 37 kb)
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Crystallographic data for compound 4-Ga. (CIF 33 kb)
Supplementary information
Crystallographic data for compound 4-In. (CIF 50 kb)
Supplementary information
Crystallographic data for compound Tl8{B(NDippCH)2}4. (CIF 50 kb)
Supplementary information
Crystallographic data for compound [K(18-crown-6)][2-Tl]. (CIF 45 kb)
Supplementary information
Crystallographic data for compound [2-Tl][B{C6H3(CF3)2-3,5}]. (CIF 116 kb)
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Protchenko, A., Dange, D., Harmer, J. et al. Stable GaX2, InX2 and TlX2 radicals. Nature Chem 6, 315–319 (2014). https://doi.org/10.1038/nchem.1870
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DOI: https://doi.org/10.1038/nchem.1870
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