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.

Actinide 2-metallabiphenylenes that satisfy Hückel’s rule

Abstract

Aromaticity and antiaromaticity, as defined by Hückel’s rule, are key ideas in organic chemistry, and are both exemplified in biphenylene1,2,3—a molecule that consists of two benzene rings joined by a four-membered ring at its core. Biphenylene analogues in which one of the benzene rings has been replaced by a different (4n + 2) π-electron system have so far been associated only with organic compounds4,5. In addition, efforts to prepare a zirconabiphenylene compound resulted in the isolation of a bis(alkyne) zirconocene complex instead6. Here we report the synthesis and characterization of, to our knowledge, the first 2-metallabiphenylene compounds. Single-crystal X-ray diffraction studies reveal that these complexes have nearly planar, 11-membered metallatricycles with metrical parameters that compare well with those reported for biphenylene. Nuclear magnetic resonance spectroscopy, in addition to nucleus-independent chemical shift calculations, provides evidence that these complexes contain an antiaromatic cyclobutadiene ring and an aromatic benzene ring. Furthermore, spectroscopic evidence, Kohn–Sham molecular orbital compositions and natural bond orbital calculations suggest covalency and delocalization of the uranium f2 electrons with the carbon-containing ligand.

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

Relevant articles

Open Access articles citing this article.

Access options

Buy article

Get time limited or full article access on ReadCube.

$32.00

All prices are NET prices.

Fig. 1: Known analogues of biphenylene.
Fig. 2: Synthetic outlines.
Fig. 3: X-ray crystallography.
Fig. 4: UV–visible spectroscopy and time-dependent DFT calculations.

Data availability

All data are available upon request from J.L.K. (synthetic and spectroscopic data) or L.G. (computational data). Crystallographic data of 4 and 5 have been uploaded to the Cambridge Crystallographic Data Centre under CCDC numbers 1526648 and 1526649.

References

  1. Karadakov, P. B., Hearnshaw, P. & Horner, K. E. Magnetic shielding, aromaticity, antiaromaticity, and bonding in the low-lying electronic states of benzene and cyclobutadiene. J. Org. Chem. 81, 11346–11352 (2016).

    CAS  Article  PubMed  Google Scholar 

  2. Balaban, A. T. & Vollhardt, K. P. C. Heliphenes and related structures. Open Org. Chem. J. 5, 117–126 (2011).

    CAS  Article  Google Scholar 

  3. Vollhardt, K. P. C. & Mohler, D. L. The phenylenes: synthesis, properties, and reactivity. Adv. Strain Org. Chem. 5, 121–160 (1996).

    CAS  Google Scholar 

  4. Lothrop, W. C. Biphenylene. J. Am. Chem. Soc. 63, 1187–1191 (1941).

  5. Garratt, P. J. & Vollhardt, K. P. C. Benzo[3,4]cyclobuta[1,2-c]thiophen (2-thianorbiphenylene). J. Chem. Soc. D., Chem. Commun. 109 (1970).

  6. Warner, B. P., Davis, W. M. & Buchwald, S. L. Synthesis and X-ray structure of a zirconocene complex of two alkynes. J. Am. Chem. Soc. 116, 5471–5472 (1994).

    CAS  Article  Google Scholar 

  7. Boese, R., Blaser, D. & Latz, R. Redetermination of biphenylene at 130 K. Acta Crystallogr. C C55, IUC9900067 (1999).

    Google Scholar 

  8. Fawcett, J. K. & Trotter, J. A Refinement of the structure of biphenylene. Acta Crystallogr. 20, 87–93 (1966).

    CAS  Article  Google Scholar 

  9. Fang, B., Hou, G., Zi, G., Fang, D.-C. & Walter, M. D. A thorium metallacyclopentadiene complex: a combined experimental and computational study. Dalton Trans. 44, 7927–7934 (2015).

    CAS  Article  PubMed  Google Scholar 

  10. Pagano, J. K., Dorhout, J. M., Waterman, R., Czerwinski, K. R. & Kiplinger, J. L. Phenylsilane as a safe, versatile alternative to hydrogen for the synthesis of actinide hydrides. Chem. Commun. 51, 17379–17381 (2015).

    CAS  Article  Google Scholar 

  11. Evans, W. J., Kozimor, S. A. & Ziller, J. W. [(C5Me5)2U][(μ-Ph)2BPh2] as a four electron reductant. Chem. Commun. 37,4681–4683 (2005).

    Article  CAS  Google Scholar 

  12. Pagano, J. K. et al. Tuning the oxidation state, nuclearity, and chemistry of uranium hydrides with phenylsilane and temperature: the case of the classic uranium(III) hydride complex [(C5Me5)2U(μ-H)]2. Organometallics 35, 617–620 (2016).

    CAS  Article  Google Scholar 

  13. Bettinger, H. F., Schleyer, P. R. & Schaefer, H. F., III. Tetraphenyldihydrocyclobutaarenes—what causes the extremely long 1.72 Å C–C single bond? Chem. Commun. 769–770 (1998).

    Article  Google Scholar 

  14. Toda, F. Naphthocyclobutenes and benzodicyclobutadienes: synthesis in the solid state and anomalies in the bond lengths. Eur. J. Org. Chem. 2000, 1377–1386 (2000).

    Article  Google Scholar 

  15. Shannon, R. D. Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides. Acta Crystallogr. A 32, 751–767 (1976).

    ADS  Article  Google Scholar 

  16. Jantunen, K. C. et al. Thorium(IV) and uranium(IV) ketimide complexes prepared by nitrile insertion into actinide–alkyl and –aryl bonds. Organometallics 23, 4682–4692 (2004).

    CAS  Article  Google Scholar 

  17. Lu, E. et al. Synthesis, characterization, and reactivity of a uranium(VI) carbene imido oxo complex. Angew. Chem. Int. Ed. 53, 6696–6700 (2014).

    CAS  Article  Google Scholar 

  18. Schleyer, P. R., Maerker, C., Dransfeld, A., Jiao, H. & van Eikema Hommes, N. J. Nucleus-independent chemical shifts: a simple and efficient aromaticity probe. J. Am. Chem. Soc. 118, 6317–6318 (1996).

    CAS  Article  PubMed  Google Scholar 

  19. Merino, G., Heine, T. & Seifert, G. The induced magnetic field in cyclic molecules. Chem. Eur. J. 10, 4367–4371 (2004).

    CAS  Article  PubMed  Google Scholar 

  20. Adamo, C. & Barone, V. Toward reliable density functional methods without adjustable parameters: the PBE0 model. J. Chem. Phys. 110, 6158–6170 (1999).

    ADS  CAS  Article  Google Scholar 

  21. Andersson, K., Malmqvist, P. Å. & Roos, B. O. Second-order perturbation theory with a complete active space self-consistent field reference function. J. Chem. Phys. 96, 1218–1226 (1992).

    ADS  CAS  Article  Google Scholar 

  22. Roos, B. O., Taylor, P. R. & Sigbahn, P. E. M. A complete active space SCF method (CASSCF) using a density matrix formulated super-CI approach. Chem. Phys. 48, 157–173 (1980).

    MathSciNet  CAS  Article  Google Scholar 

  23. Heit, Y. N., Gendron, F. & Autschbach, J. Calculation of dipole-forbidden 5f absorption spectra of uranium(V) hexa-halide complexes. J. Phys. Chem. Lett. 9, 887–894 (2018).

    CAS  Article  PubMed  Google Scholar 

  24. Lever, A. B. P. (ed.) Inorganic Electronic Spectroscopy 2nd edn, Ch. 4, 161–202 (Elsevier, 1999).

  25. Pagano, J. K. et al. Synthesis and characterization of a new and electronically unusual uranium metallacyclocumulene, (C5Me5)2U(η4-1,2,3,4-PhC4Ph). J. Organomet. Chem. 829, 79–84 (2017).

    CAS  Article  Google Scholar 

  26. Morris, D. E., Da Re, R. E., Jantunen, K. C., Castro-Rodriguez, I. & Kiplinger, J. L. Trends in electronic structure and redox energetics for early-actinide pentamethylcyclopentadienyl complexes. Organometallics 23, 5142–5153 (2004).

    CAS  Article  Google Scholar 

  27. Cantat, T., Scott, B. L., Morris, D. E. & Kiplinger, J. L. What a difference a 5f element makes: trivalent and tetravalent uranium halide complexes supported by one and two bis[2-(diisopropylphosphino)-4-methylphenyl]amido (PNP) ligands. Inorg. Chem. 48, 2114–2127 (2009).

    CAS  Article  PubMed  Google Scholar 

  28. Schelter, E. J. et al. Actinide redox-active ligand complexes: reversible intramolecular electron-transfer in U(dpp-BIAN)2/U(dpp-BIAN)2(THF). Inorg. Chem. 49, 924–933 (2010).

    CAS  Article  PubMed  Google Scholar 

  29. Schelter, E. J. et al. Systematic studies of early actinide complexes: uranium(IV) fluoroketimides. Inorg. Chem. 46, 7477–7488 (2007).

    CAS  Article  PubMed  Google Scholar 

  30. Cantat, T. et al. Evidence for the involvement of 5f orbitals in the bonding and reactivity of organometallic actinide compounds: thorium(IV) and uranium(IV) bis(hydrazonato) complexes. J. Am. Chem. Soc. 130, 17537–17551 (2008).

    CAS  Article  PubMed  Google Scholar 

  31. Da Re, R. E., Jantunen, K. C., Golden, J. T., Kiplinger, J. L. & Morris, D. E. Molecular spectroscopy of uranium(IV) bis(ketimido) complexes. Rare observation of resonance-enhanced Raman scattering from organoactinide complexes and evidence for broken-symmetry excited states. J. Am. Chem. Soc. 127, 682–689 (2005).

    Article  CAS  Google Scholar 

  32. Minasian, S. G. et al. New evidence for 5f covalency in actinocenes determined from carbon K-edge XAS and electronic structure theory. Chem. Sci. 5, 351–359 (2014).

    CAS  Article  Google Scholar 

  33. Peterson, P. W. et al. Orbital crossings activated through electron injection: opening communication between orthogonal orbitals in anionic C1–C5 cyclizations of enediynes. J. Am. Chem. Soc. 138, 15617–15628 (2016).

    CAS  Article  PubMed  Google Scholar 

  34. Fagan, P. J., Manriquez, J. M., Maatta, E. A., Seyam, A. M. & Marks, T. J. Synthesis and properties of bis(pentamethylcyclopentadienyl) actinide hydrocarbyls and hydrides. A new class of highly reactive f-element organometallic compounds. J. Am. Chem. Soc. 103, 6650–6667 (1981).

    CAS  Article  Google Scholar 

  35. APEX2 v.2014.7-1 (Bruker AXS, 2014).

  36. SAINT v.8.34A (Bruker AXS, 2013).

  37. SADABS v.2014/3 (Bruker AXS, 2013).

  38. SHELXTL v.6.14 (Bruker AXS, 2000).

  39. Gaussian 09, revision E.01 (Gaussian Inc., 2009).

  40. Becke, A. D. Density-functional thermochemistry. III. The role of exact exchange. J. Chem. Phys. 98, 5648–5652 (1993).

    ADS  CAS  Article  Google Scholar 

  41. Su, J. et al. Energy-degeneracy-driven covalency in actinide bonding. J. Am. Chem. Soc. 140, 17977–17984 (2018).

    CAS  Article  PubMed  Google Scholar 

  42. Vukovic, S., Hay, B. P. & Bryantsev, V. S. Predicting stability constants for uranyl complexes using density functional theory. Inorg. Chem. 54, 3995–4001 (2015).

    CAS  Article  PubMed  Google Scholar 

  43. Hu, H.-S., Wei, F., Wang, X., Andrews, L. & Li, J. Actinide–silicon multiradical bonding: infrared spectra and electronic structures of the Si(μ-X)AnF3 (An = Th, U; X = H, F) molecules. J. Am. Chem. Soc. 136, 1427–1437 (2014).

    CAS  Article  PubMed  Google Scholar 

  44. Safi, S. et al. Osteopontin: a uranium phosphorylated binding-site characterization. Chem. Eur. J. 19, 11261–11269 (2013).

    CAS  Article  PubMed  Google Scholar 

  45. Minasian, S. G. et al. Determining relative f and d orbital contributions to M–Cl covalency in MCl6 2– (M = Ti, Zr, Hf, U) and UOCl5 using Cl K-edge X-ray absorption spectroscopy and time-dependent density functional theory. J. Am. Chem. Soc. 134, 5586–5597 (2012).

    CAS  Article  PubMed  Google Scholar 

  46. Tsushima, S., Brendler, V. & Fahmy, K. Aqueous coordination chemistry and photochemistry of uranyl (VI) oxalate revisited: a density functional theory study. Dalton Trans. 39, 10953–10958 (2010).

    CAS  Article  PubMed  Google Scholar 

  47. Kubicki, J. D., Halada, G. P., Jha, P. & Phillips, B. L. Quantum mechanical calculation of aqueous uranium complexes: carbonate, phosphate, organic and biomolecular species. Chem. Cent. J. 3, 10 (2009).

    PubMed  PubMed Central  Article  CAS  Google Scholar 

  48. Graves, C. R. et al. Organometallic uranium(V)−imido halide complexes: from synthesis to electronic structure and bonding. J. Am. Chem. Soc. 130, 5272–5285 (2008).

    CAS  Article  PubMed  Google Scholar 

  49. Gutowski, K. E. et al. Interactions of 1-methylimidazole with UO2(CH3CO2)2 and UO2(NO3)2: structural, spectroscopic, and theoretical evidence for imidazole binding to the uranyl ion. J. Am. Chem. Soc. 129, 526–536 (2007).

    CAS  Article  PubMed  Google Scholar 

  50. Cao, X., Dolg, M. & Stoll, H. Valence basis sets for relativistic energy-consistent small-core actinide pseudopotentials. J. Chem. Phys. 118, 487–496 (2003).

    ADS  CAS  Article  Google Scholar 

  51. Hehre, W. J., Ditchfield, R. & Pople, J. A. Self-consistent molecular orbital methods. XII. Further extensions of Gaussian-type basis sets for use in molecular orbital studies of organic molecules. J. Chem. Phys. 56, 2257–2261 (1972).

    ADS  CAS  Article  Google Scholar 

  52. Krishnan, R., Binkley, J. S., Seeger, R. & Pople, J. A. Self-consistent molecular orbital methods. XX. A basis set for correlated wave functions. J. Chem. Phys. 72, 650–654 (1980).

    ADS  CAS  Article  Google Scholar 

  53. Weigend, F. & Ahlrichs, R. Balanced basis sets of split valence, triple zeta valence and quadruple zeta valence quality for H to Rn: design and assessment of accuracy. Phys. Chem. Chem. Phys. 7, 3297–3305 (2005).

    CAS  Article  PubMed  Google Scholar 

  54. Yanai, T., Tew, D. P. & Handy, N. C. A new hybrid exchange-correlation functional using the Coulomb-attenuating method (CAM-B3LYP). Chem. Phys. Lett. 393, 51–57 (2004).

    ADS  CAS  Article  Google Scholar 

  55. Perdew, J. P., Burke, K. & Ernzerhof, M. Generalized gradient approximation made simple. Phys. Rev. Lett. 77, 3865–3868 (1996).

    ADS  CAS  PubMed  Article  Google Scholar 

  56. Zhao, Y. & Truhlar, D. G. A new local density functional for main-group thermochemistry, transition metal bonding, thermochemical kinetics, and noncovalent interactions. J. Chem. Phys. 125, 194101 (2006).

    ADS  Article  CAS  PubMed  Google Scholar 

  57. Wolinski, K., Hinton, J. F. & Pulay, P. Efficient implementation of the gauge-independent atomic orbital method for NMR chemical shift calculations. J. Am. Chem. Soc. 112, 8251–8260 (1990).

    CAS  Article  Google Scholar 

  58. Andersson, K., Malmqvist, P. A., Roos, B. O., Sadlej, A. J. & Wolinski, K. Second-order perturbation theory with a CASSCF reference function. J. Phys. Chem. 94, 5483–5488 (1990).

    CAS  Article  Google Scholar 

  59. Aquilante, F. et al. MOLCAS 8: new capabilities for multiconfigurational quantum chemical calculations across the periodic table. J. Comput. Chem. 37, 506–541 (2016).

    CAS  Article  PubMed  Google Scholar 

  60. Roos, B. O., Lindh, R., Malmqvist, P. Å., Veryazov, V. & Widmark, P. O. Main group atoms and dimers studied with a new relativistic ano basis set. J. Phys. Chem. A 108, 2851–2858 (2004).

    CAS  Article  Google Scholar 

  61. Roos, B. O., Lindh, R., Malmqvist, P. Å., Veryazov, V. & Widmark, P. O. New relativistic ano basis sets for actinide atoms. Chem. Phys. Lett. 409, 295–299 (2005).

    ADS  CAS  Article  Google Scholar 

  62. Douglas M. & Kroll, N. M. Quantum electrodynamical corrections to fine-structure of helium. Ann. Phys. 82, 89–155 (1974).

    ADS  CAS  Article  Google Scholar 

  63. Hess, B. A. Applicability of the no-pair equation with free-particle projection operators to atomic and molecular-structure calculations. Phys. Rev. A 32, 756–763 (1985).

    ADS  CAS  Article  Google Scholar 

  64. Aquilante, F., Pedersen, T. B. & Lindh, R. Unbiased auxiliary basis sets for accurate two-electron integral approximations. J. Chem. Phys. 127, 114107 (2007).

    ADS  Article  CAS  PubMed  Google Scholar 

  65. Marenich, A. V., Cramer, C. J. & Truhlar, D. G. Universal solvation model based on solute electron density and on a continuum model of the solvent defined by the bulk dielectric constant and atomic surface tensions. J. Phys. Chem. B 113, 6378–6396 (2009).

    CAS  Article  PubMed  Google Scholar 

Download references

Acknowledgements

For financial support of this work, we acknowledge the US Department of Energy (DOE) through the Los Alamos National Laboratory (LANL) Laboratory Directed Research and Development Program; the LANL G. T. Seaborg Institute for Transactinium Science (Postdoctoral Fellowships to J.K.P., K.A.E. and S.K.C.); the Office of Workforce Development for Teachers and Scientists, Office of Science Graduate Student Research (SCGSR) program (GRA Fellowship to J.K.P.); and the Office of Basic Energy Sciences, Heavy Element Chemistry program (to J.L.K., P.Y. and B.L.S., for materials and supplies). We thank R. Michalczyk and L. A. Silks (LANL) for assistance with two-dimensional NMR experiments, and J. Thompson and P. Rosa (LANL) for assistance in collecting magnetometry data. This work was in part funded by the Division of Chemical Sciences, Geosciences, and Biosciences, Office of Basic Energy Sciences of the US DOE through grant USDOE/DESC002183 (to J.X. and L.G.). We also acknowledge the US National Science Foundation (grants CHE-1265608 and CHE-1565658 to R. Waterman). The SCGSR program is administered by the Oak Ridge Institute for Science and Education for the DOE (contract DE-AC05-06OR23100). LANL is operated by Los Alamos National Security, LLC, for the National Nuclear Security Administration of the US DOE (contract DE-AC52-06NA25396).

Author information

Authors and Affiliations

Authors

Contributions

J.K.P. synthesized and fully characterized compounds 4 and 5, including collecting and solving single-crystal X-ray data. J.X. performed computational calculations and wrote the calculation part of the manuscript. J.X. used the Minnesota Supercomputing Institute (University of Minnesota) for computational resources. K.A.E. provided the alternative synthesis of compound 5 and spectroscopically characterized compound 1. S.K.C. performed two-dimensional NMR experiments on compounds 4 and 5 and interpreted the data. D.E.M. interpreted electronic spectra and wrote that section of the manuscript. B.L.S. maintained the X-ray facility and provided assistance with solutions. R. Wu synthesized 1,2-bis(phenylethynyl)benzene. P.Y. assisted with time-dependent DFT calculations on compounds 4 and 5. J.K.P., J.X., K.A.E. and J.L.K. wrote the initial manuscript. J.L.K. and R. Waterman supervised the synthetic research. D.E.M. and J.L.K. supervised the spectroscopic characterization. L.G. supervised the computational calculations. J.L.K. initiated the research. All authors edited the manuscript.

Corresponding authors

Correspondence to David E. Morris, Ping Yang, Laura Gagliardi or Jaqueline L. Kiplinger.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Peer review information Nature thanks Joy Farnaby and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Extended data figures and tables

Extended Data Fig. 1 NIR spectroscopy as a covalency indicator.

NIR spectra of U(iv)-containing compounds 5 and 7 collected in toluene at 298 K. Band energies and relative intensities are strongly correlated in these spectra, but the absolute intensities in the bands for 5 are around two to four times those in the bands for 7, which suggests a greater degree of U–C covalency.

Extended Data Fig. 2 NICS profiles to assess aromaticity/antiaromaticity.

A, NICS and Bindz values were computed in the axis perpendicular to the four-membered ring and six-membered ring planes of compounds 4 and 5. The points at which the shielding tensors were calculated are represented here by small blue spheres; the points pass through the corresponding non-mass-weighted centre of each ring. BD, NICS and Bindz profiles of the four-membered ring and six-membered ring for compounds 4 (B; An = Th), 5 (C; An = U), and cyclobutadiene and benzene (D). The PBE0/6-31G(d,p)&SDD level of theory was used. R is the distance from the centre of each ring along the axis, in Å.

Extended Data Fig. 3 NICS profiles of classic compounds to assess aromaticity/antiaromaticity.

AD, NICS and Bindz profiles of the four-membered ring and six-membered ring for biphenylene (1) (A), 2-thianorbiphenylene (2) (B), 2-thianorbiphenylene sulfone (3) (C), and benzo[3,4]cyclobuta[1,2]furan (D).

Extended Data Fig. 4 Calculated Kohn–Sham molecular orbitals of compound 5.

Molecular orbitals for triplet (C5Me5)2U(2,5-Ph2-cyclopenta[3,4]cyclobuta[1,2]benzene) (5-triplet) as computed with PBE0/631G(d,p)&SDD. An isocontour value of 0.04 was used. The left column shows the α-spin molecular orbitals and the right column shows the β-spin molecular orbitals. For both spins, the orbitals are labelled according to their energetic order among those of the same spin. Orbitals are paired here with the closest corresponding orbital of the opposite spin. The positive and negative phases of the Kohn–Sham molecular orbitals are in red and blue, respectively.

Extended Data Fig. 5 Calculated active molecular orbitals and natural bond orbitals.

AF, Active molecular orbitals for the CAS(6,6) model of 5a-triplet (An = U) in its triplet ground spin state, with the occupation number given in parentheses. The positive and negative phases of the active molecular orbitals are in blue and white. GI, Representative natural bond orbitals for 5-triplet (An = U) in the triplet state. The positive and negative phases of the natural bond orbitals are in red and yellow. U, green; C, silver. H atoms are omitted for clarity.

Supplementary information

Supplementary Information

This file includes Experimental SI, Figures S1–S9, Table S1, Computational SI, Figures S10–S20, Tables S2–S18 and Calculated Structures Coordinates.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Pagano, J.K., Xie, J., Erickson, K.A. et al. Actinide 2-metallabiphenylenes that satisfy Hückel’s rule. Nature 578, 563–567 (2020). https://doi.org/10.1038/s41586-020-2004-7

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/s41586-020-2004-7

Further reading

Comments

By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.

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