Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Ultrashort metal–metal distances and extreme bond orders

Abstract

Chemical bonding is at the very heart of chemistry. Although main-group-element E–E′ bond orders range up to triple bonds, higher formal bond orders are known between transition metals. Here we review recent developments related to the synthesis of formally quintuply bonded transition metals in coordination compounds, and their theoretical description. The quadruple bond fascinated chemists for about 40 years. Recently, a stable molecule containing a formal quintuple bond initiated a renaissance in synthesizing and understanding bonds with high bond orders. Ultrashort metal–metal distances as low as 1.73 Å are one of the outcomes. First results indicate that the relevance of these bimetallic platforms to synthetic chemistry can be addressed through quintuple-bond reactivity studies. The theoretical description of the bonding situation in molecules with extreme bond orders has only just begun.

This is a preview of subscription content, access via your institution

Access options

Rent or buy this article

Prices vary by article type

from$1.95

to$39.95

Prices may be subject to local taxes which are calculated during checkout

Figure 1: Quadruple bonding in chromium homobimetallic complexes.
Figure 2: Molecular structure of the first stable compound in which quintuple bonding was observed.
Figure 3: Homobimetallic chromium compounds in which unusually short metal–metal distances were observed.
Figure 4: The role of the ligand in stabilizing ultrashort metal–metal bonds.
Figure 5: Molecular structure of the coordination compounds with the shortest metal–metal bond so far observed.
Figure 6: Carboalumination of a Cr–Cr quintuple bond.

References

  1. Pauling, L. The Nature of the Chemical Bond 3rd edn (VCH, 1973).

    Google Scholar 

  2. Lewis, G. N. The atom and the molecule. J. Am. Chem. Soc. 38, 762–785 (1916).

    Article  CAS  Google Scholar 

  3. Shaik, S. The Lewis legacy: the chemical bond—a territory and heartland of chemistry. J. Comput. Chem. 28, 51–61 (2007).

    Article  CAS  PubMed  Google Scholar 

  4. Heitler, W. & London, F. Interaction of neutral atoms and homopolar binding according to the quantum mechanics. Z. Phys. 44, 455–472 (1927).

    Article  CAS  Google Scholar 

  5. London, F. The quantum theory of monopolar valence numbers. Z. Phys. 46, 455–477 (1928).

    Article  CAS  Google Scholar 

  6. Cotton, F. A., Murillo, L. A. & Walton, R. A. Multiple Bonds Between Metal Atoms 3rd edn (Springer, 2005).

    Book  Google Scholar 

  7. Nguyen, T. et al. Synthesis of a stable compound with fivefold bonding between two chromium(I) centers. Science 310, 844–847 (2005).

    Article  CAS  PubMed  Google Scholar 

  8. Ruedenberg, K. & Schmidt, M. W. Why does electron sharing lead to covalent bonding? A variational analysis. J. Comput. Chem. 28, 391–410 (2007).

    Article  CAS  PubMed  Google Scholar 

  9. Kutzelnigg, W. in Theoretical Models of Chemical Bonding, Part 2: The Concept of the Chemical Bond (ed. Maksić, Z. B.) 1–43 (Springer, 1990).

    Google Scholar 

  10. Parr, R. G., Ayers, P. W. & Nalewajski, R. F. What is an atom in a molecule? J. Phys. Chem. A 109, 3957–3959 (2005).

    Article  CAS  PubMed  Google Scholar 

  11. Bader, R. F. W. Atoms in Molecules: A Quantum Theory (Clarendon, 1995).

    Google Scholar 

  12. Hirshfeld, F. L. Bonded-atom fragments for describing molecular charge densities. Theor. Chem. Acc. 44, 129–138 (1977).

    Article  CAS  Google Scholar 

  13. Hoffmann, R., Shaik, S. & Hiberty, P. C. A conversation on VB vs. MO theory: a never-ending rivalry? Acc. Chem. Res. 36, 750–756 (2003).

    Article  CAS  PubMed  Google Scholar 

  14. Frenking, G. & Krapp, A. Unicorns in the world of chemical bonding models. J. Comput. Chem. 28, 15–24 (2007).

    Article  CAS  PubMed  Google Scholar 

  15. Herzberg, G. Zum Aufbau der zweiatomigen Moleküle. Z. Phys. 57, 601–630 (1929).

    Article  CAS  Google Scholar 

  16. Mulliken, R. S. Bonding power of electrons and theory of valence. Chem. Rev. 9, 347–388 (1931).

    Article  CAS  Google Scholar 

  17. Mulliken, R. S. Electronic structure of polyatomic molecules and valence. II. General considerations. Phys. Rev. 41, 49–71 (1932).

    Article  CAS  Google Scholar 

  18. Hall, M. B. Problems in the theoretical description of metal–metal multiple bonds or how I learned to hate the electron correlation problem. Polyhedron 6, 679–684 (1987).

    Article  CAS  Google Scholar 

  19. Roos, B. O., Malmqvist, P.-A. & Gagliardi, L. Exploring the actinide–actinide bond in Ac2, Th2, Pa2, and U2 . J. Am. Chem. Soc. 128, 17000–17006 (2006).

    Article  CAS  PubMed  Google Scholar 

  20. Coulson, C. A. The electronic structure of some polyenes and aromatic molecules VII. Bonds of fractional order by the molecular orbital method. Proc. R. Soc. Lond. A 169, 413–428 (1939).

    Article  CAS  Google Scholar 

  21. Pauling, L., Brockway, L. O. & Beach, J. Y. The dependence of interatomic distance on single-bond-double-bond resonance. J. Am. Chem. Soc. 57, 2705–2709 (1935).

    Article  CAS  Google Scholar 

  22. Glendening, E. D. & Weinhold, F. Natural resonance theory: I. General formalism. J. Comput. Chem. 19, 593–609 (1998); Natural resonance theory: II. Natural bond order and valency. J. Comput. Chem. 19, 610–627 (1998); Natural resonance theory: III. Chemical applications. J. Comput. Chem. 19, 628–646 (1998).

    Article  CAS  Google Scholar 

  23. Weinhold, F. & Landis, C. Valence and Bonding: A Natural Bond Orbital Donor-Acceptor Perspective 1st edn (Cambridge Univ. Press, 2005).

    Book  Google Scholar 

  24. McWeeny, R. Charge densities in conjugated systems. J. Chem. Phys. 19, 1614–1615 (1951).

    Article  CAS  Google Scholar 

  25. Mulliken, R. S. Electronic population analysis on LCAO-MO molecular wave functions. I. J. Chem. Phys. 23, 1833–1840 (1955).

    Article  CAS  Google Scholar 

  26. Giambiagi, M., de Giambiagi, M. S., Grempel, D. R. & Heynmann, C. D. No. 3 – Sur la definition d'un indice de liaison (TEV) pour des bases non orthogonales. Proprietes et applications. J. Chim. Phys. 72, 15–22 (1975).

    Article  CAS  Google Scholar 

  27. Mayer, I. Charge, bond order and valence in the SCF theory. Chem. Phys. Lett. 97, 270–274 (1983).

    Article  CAS  Google Scholar 

  28. Wiberg, K. B. Application of the Pople-Santry-Segal CNDO method to the cyclopropylcarbinyl and cyclobutyl cation and to bicyclobutane. Tetrahedron 24, 1083–1096 (1968).

    Article  CAS  Google Scholar 

  29. Mayer, I. Bond orders and valence indices: a personal account. J. Comput. Chem. 28, 204–221 (2007).

    Article  CAS  PubMed  Google Scholar 

  30. De Giambiagi, M. S., Giambiagi, M. & Jorge, F. E. Bond index: relation to second order density matrix and charge fluctuations. Theor. Chim. Acta 68, 337–341 (1985).

    Article  CAS  Google Scholar 

  31. Bader, R. F. W. & Stephens, M. E. Spatial localization of the electron pair and number distributions in molecules. J. Am. Chem. Soc. 97, 7391–7399 (1975).

    Article  CAS  Google Scholar 

  32. Ángyán, J. G., Loos, M. & Mayer, I. Covalent bond orders and atomic valence indices in the topological theory of atoms in molecules. J. Phys. Chem. 98, 5244–5248 (1994).

    Article  Google Scholar 

  33. Matito, E., Mayer, I. & Solà, M. General discussion. Faraday Discuss. 135, 367–401 (2007).

    Article  Google Scholar 

  34. Fradera, X., Austen, M. A. & Bader, R. F. W. The Lewis model and beyond. J. Phys. Chem. A 103, 304–314 (1999).

    Article  CAS  Google Scholar 

  35. Matito, E., Solà, M., Salvador, P. & Duran, M. Electron sharing indexes at the correlated level. Application to aromaticity calculations. Faraday Discuss. 135, 325–345 (2007).

    Article  CAS  PubMed  Google Scholar 

  36. Fradera, X., Poater, J., Simon, S., Duran, M. & Solà, M. Electron-pairing analysis from localization and delocalization indices in the framework of the atoms-in-molecules theory. Theor. Chem. Acc. 108, 214–224 (2002).

    Article  CAS  Google Scholar 

  37. Peligot, E. Sur un nouvel oxide de chrome. C. R. Acad. Sci. 19, 609–618 (1844); Recherches sur le chrome. Ann. Chim. Phys. 12, 528–579 (1844).

    Google Scholar 

  38. Cotton, F. A., Curtis, N. F., Johnson, B. F. G. & Robinson, W. R. Compounds containing dirhenium(III) octahalide anions. Inorg. Chem. 4, 326–330 (1965).

    Article  CAS  Google Scholar 

  39. Cotton, F. A. & Harris, C. B. The crystal and molecular structure of dipotassium octachlorodirhenate(III) dihydrate, K2[Re2Cl8]·2H2O. Inorg. Chem. 4, 330–333 (1965).

    Article  CAS  Google Scholar 

  40. Cotton, F. A. Metal-metal bonding in [Re2X8]2− ions and other metal atom clusters. Inorg. Chem. 4, 334–336 (1965).

    Article  CAS  Google Scholar 

  41. Cotton, F. A. et al. Mononuclear and polynuclear chemistry of rhenium(III): its pronounced homophilicity. Science 145, 1305–1307 (1964).

    Article  CAS  PubMed  Google Scholar 

  42. Kotel'nikov, A. S. & Tronev, V. G. Study of the complex compounds of divalent rhenium. J. Inorg. Chem. USSR 3, 1008–1027 (1958).

    Google Scholar 

  43. Kuznetzov, B. G. & Koz'min, P. A. The determination of the structure of (PyH)HReCl4. Zh. Strukt. Khim. 4, 55–62 (1963).

    Google Scholar 

  44. Trogler, W. C. & Gray, H. B. Electronic spectra and photochemistry of complexes containing quadruple metal–metal bonds. Acc. Chem. Res. 11, 232–239 (1978).

    Article  CAS  Google Scholar 

  45. Gagliardi, L. & Roos, B. O. The electronic spectrum of Re2Cl82−: a theoretical study. Inorg. Chem. 42, 1599–1603 (2003).

    Article  CAS  PubMed  Google Scholar 

  46. Krapp, A., Lein, M. & Frenking, G. The strength of the σ-, π- and δ-bonds in Re2Cl82−. Theor. Chem. Acc. 120, 313–320 (2008).

    Article  CAS  Google Scholar 

  47. Cotton, F. A. & Koch, S. A. Rational preparation and structural study of a dichromium o-oxophenyl compound: the shortest metal-to-metal bond yet observed. Inorg. Chem. 17, 2021–2024 (1978).

    Article  CAS  Google Scholar 

  48. Hein, F. & Tille, D. Zur Existenz substituierter Chromphenylverbindungen. Z. Anorg. Allg. Chem. 329, 72–82 (1964).

    Article  CAS  Google Scholar 

  49. Cotton, F. A., Koch, S. A. & Millar, M. Tetrakis(2-methoxy-5-methylphenyl)dichromium. Inorg. Chem. 17, 2084–2086 (1978).

    Article  CAS  Google Scholar 

  50. Edema, J. H. H. & Gambarotta, S. Short and supershort Cr–Cr distances: a vanishing borderline between metal–metal bonds, magnetic coupling and ligand artefacts. Comments. Inorg. Chem. 11, 195–214 (1991).

    CAS  Google Scholar 

  51. Edema, J. H. H., Gambarotta, S., Van der Sluis, P., Smeets, W. J. J. & Spek, A. L. Preparation and X-ray structure of (tetramethyldibenzotetraaza[14]annulene)chromium dimer [(tmtaa)Cr]2. A multiply bonded complex of dichromium(II) without bridging ligands. Inorg. Chem. 28, 3782–3784 (1989).

    Article  CAS  Google Scholar 

  52. Hao, S., Edema, J. H. H., Gambarotta, S. & Bensimon, C. Reversible cleavage of the chromium–chromium multiple bond in [(TAA)Cr]2 (TAA = tetramethyldibenzotetraaza[14]annulene). Inorg. Chem. 31, 2676–2678 (1992).

    Article  CAS  Google Scholar 

  53. Horvath, S., Gorelsky, S. I., Gambarotta, S. & Korobkov, I. Breaking the 1.80 Å barrier of the Cr–Cr multiple bond between CrII atoms. Angew. Chem. Int. Ed. 47, 9937–9940 (2008).

    Article  CAS  Google Scholar 

  54. Künding, E. P., Moskovits, M. & Ozin, G. A. Matrix synthesis and characterisation of dichromium. Nature 254, 503–504 (1975).

    Article  Google Scholar 

  55. Klotzbücher, W. & Ozin, G. A. Niniobium, Nb2, and dimolybdenum, Mo2. Syntheses, ultraviolet-visible spectra and molecular orbital investigations of diniobium and dimolybdenum. Spectral and bonding comparison with divanadium (V2) and dichromium (Cr2). Inorg. Chem. 16, 984–987 (1977).

    Article  Google Scholar 

  56. Bondybey, V. E. & English, J. H. Electronic structure and vibrational frequency of diatomic chromium (Cr2). Chem. Phys. Lett. 94, 443–447 (1983).

    Article  CAS  Google Scholar 

  57. Efremov, Yu. M., Samoilova, A. N. & Gurvich, L. V. The λ = 4600 Å band in a spectrum by pulsed photolysis of chromium carbonyl. Opt. Spektrosc. 36, 654–657 (1974).

    CAS  Google Scholar 

  58. Morse, M. D. Clusters of transition metal atoms. Chem. Rev. 86, 1049–1109 (1986).

    Article  CAS  Google Scholar 

  59. Schiemenz, B. & Power, P. P. Synthesis and structure of a unique monomeric σ-bonded aryllithium compound stabilized by a weak Li-benzene π interaction. Angew. Chem. Int. Edn Engl. 35, 2150–2152 (1996).

    Article  CAS  Google Scholar 

  60. La Macchia, G., Gagliardi, L., Power, P. P. & Brynda, M. Large differences in secondary metal–arene interactions in the transition-metal dimers ArMMAr (Ar = Terphenyl; M = Cr, Fe, or Co): implications for Cr–Cr quintuple bonding. J. Am. Chem. Soc. 130, 5104–5114 (2008).

    Article  CAS  PubMed  Google Scholar 

  61. Frenking, G. Building a quintuple bond. Science 310, 796–797 (2005).

    Article  CAS  PubMed  Google Scholar 

  62. Landis, C. R. & Weinhold, F. Origin of trans-bent geometries in maximally bonded transition metal and main group molecules. J. Am. Chem. Soc. 128, 7335–7345 (2006).

    Article  CAS  PubMed  Google Scholar 

  63. Merino, G., Donald, K. J., D'Acchioli, J. S. & Hoffmann, R. The many ways to have a quintuple bond. J. Am. Chem. Soc. 129, 15295–15302 (2007).

    Article  CAS  PubMed  Google Scholar 

  64. Brynda, M., Gagliardi, L., Widmark, P.-O., Power, P. P. & Roos, B. O. A quantum chemical study of the quintuple bond between two chromium centers in [PhCrCrPh]: trans-bent versus linear geometry. Angew. Chem. Int. Ed. 45, 3804–3807 (2006).

    Article  CAS  Google Scholar 

  65. Roos, B. O. The ground state potential for the chromium dimer revisited. Collect. Czech. Chem. Commun. 68, 265–274 (2003).

    Article  CAS  Google Scholar 

  66. Kreisel, K. A., Yap, G. P. A., Dmitrenko, O., Landis, C. R. & Theopold, K. H. The shortest metal–metal bond yet: molecular and electronic structure of a dinuclear chromium diazadiene complex. J. Am. Chem. Soc. 129, 14162–14163 (2007).

    Article  CAS  PubMed  Google Scholar 

  67. DuPré, D. Multiple bonding in the chromium dimer supported by two diazadiene ligands. J. Phys. Chem. A 113, 1559–1563 (2009).

    Article  PubMed  CAS  Google Scholar 

  68. La Macchia, G., Aquilante, F., Veryazov, V., Roos, B. O. & Gagliardi, L. Bond length and bond order in one of the shortest Cr–Cr bonds. Inorg. Chem. 47, 11455–11457 (2008).

    Article  CAS  PubMed  Google Scholar 

  69. Wolf, R. et al. Substituent effects in formally quintuple bonded ArCrCrAr compounds (Ar = terphenyl) and related species. Inorg. Chem. 46, 11277–11290 (2007).

    Article  CAS  PubMed  Google Scholar 

  70. Noor, A., Wagner, F. R. & Kempe, R. Metal–metal distances at the limit:a coordination compound with an ultrashort chromium–chromium bond. Angew. Chem. Int. Ed. 47, 7246–7249 (2008).

    Article  CAS  Google Scholar 

  71. Tsai, Y.-C. et al. Remarkably short metal–metal bonds: a lantern-type quintuply bonded dichromium(I) complex. Angew. Chem. Int. Ed. 47, 7250–7253 (2008).

    Article  CAS  Google Scholar 

  72. Hsu, C.-W. et al. Quintuply-bonded dichromium(I) complexes featuring metal–metal bond lengths of 1.74 Å. Angew. Chem. Int. Ed. 47, 9933–9936 (2008).

    Article  CAS  Google Scholar 

  73. Kohout, M. Bonding indicators from electron pair density functionals. Faraday Discuss. 135, 43–54 (2007).

    Article  CAS  PubMed  Google Scholar 

  74. Wagner, F. R., Bezugly, V., Kohout, M. & Grin, Yu. Charge decomposition of the electron localizability indicator - a bridge between the direct and Hilbert space representation of the chemical bond. Chem. Eur. J. 13, 5724–5741 (2007).

    Article  CAS  PubMed  Google Scholar 

  75. Llusar, R., Beltrán, A., Andrés, J., Fuster, F. & Silvi, B. Topological analysis of multiple metal–metal bonds in dimers of the M2(formamidinate)4 type withM = Nb, Mo, Tc, Ru, Rh, and Pd. J. Phys. Chem. A 105, 9460–9466 (2001).

    Article  CAS  Google Scholar 

  76. Ge, S., Meetsma, A. & Hessen, B. Highly efficient hydrosilylation of alkenes by organoyttrium catalysts with sterically demanding amidinate and guanidinate ligands. Organometallics 27, 3131–3135 (2008).

    Article  CAS  Google Scholar 

  77. Noor, A. et al. Metal-metal distances at the limit: Cr-Cr 1.73 Å - the importance of the ligand and its fine tuning. Z. Anorg. Allg. Chem. 635, 1149–1152 (2009).

    Article  CAS  Google Scholar 

  78. Brynda, M., Gagliardi, L. & Roos, B. O. Analysing the chromium–chromium multiple bonds using multiconfigurational quantum chemistry. Chem. Phys. Lett. 471, 1–10 (2009).

    Article  CAS  Google Scholar 

  79. Gorokhov, L. N., Emelyanov, A. M. & Khodeev, Y. S. Mass-spectroscopic investigation of stability of gaseous molecules of U2O2 and U2 . High Temp. 12, 1156–1158 (1974).

    Google Scholar 

  80. Gagliardi, L. & Roos, B. O. Quantum chemical calculations show that the uranium molecule U2 has a quintuple bond. Nature 433, 848–851 (2005).

    Article  CAS  PubMed  Google Scholar 

  81. Glukhovtsev, M. N. & v Schleyer, P. R. Polyatomic molecules without electron-pair bonds: high-spin trigonal, tetrahedral, and octahedral lithium clusters. Isr. J. Chem. 33, 455–466 (1993).

    Article  CAS  Google Scholar 

  82. Roos, B. O., Borin, A. C. & Gagliardi, L. Reaching the maximum multiplicity of the covalent bond. Angew. Chem. Int. Ed. 46, 1469–1472 (2007).

    Article  CAS  Google Scholar 

  83. Noor, A., Glatz, G., Müller, R., Kaupp, M., Demeshko, S. & Kempe, R. Carboalumination of a chromium–chromium quintuple bond. Nature Chem. 1, 322–325 (2009).

    Article  CAS  Google Scholar 

  84. Ni, C., Ellis, B. D., Long, G. J., Power, P. P. Reactions of Ar′CrCrAr′ with N2O or N3(1-Ad) : complete cleavage of the Cr–Cr quintuple interaction. Chem. Commun. 2332–2334 (2009).

  85. Tsai, Y.-C. et al. Journey from Mo–Mo quadruple bonds to quintuple bonds. J. Am. Chem. Soc. 131, 12534–12535 (2009).

    Article  CAS  PubMed  Google Scholar 

Download references

Author information

Authors and Affiliations

Authors

Corresponding authors

Correspondence to Frank R. Wagner or Rhett Kempe.

Rights and permissions

Reprints and permissions

About this article

Cite this article

Wagner, F., Noor, A. & Kempe, R. Ultrashort metal–metal distances and extreme bond orders. Nature Chem 1, 529–536 (2009). https://doi.org/10.1038/nchem.359

Download citation

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/nchem.359

This article is cited by

Search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing