Actinide 2-metallabiphenylenes that satisfy Hückel's rule

Justin K Pagano; Jing Xie; Karla A Erickson; Stephen K Cope; Brian L Scott; Ruilian Wu; Rory Waterman; David E Morris; Ping Yang; Laura Gagliardi; Jaqueline L Kiplinger

doi:10.1038/s41586-020-2004-7

Actinide 2-metallabiphenylenes that satisfy Hückel's rule

Nature. 2020 Feb;578(7796):563-567. doi: 10.1038/s41586-020-2004-7. Epub 2020 Feb 26.

Authors

Justin K Pagano^#^{1

2}, Jing Xie^#^{3

4}, Karla A Erickson¹, Stephen K Cope¹, Brian L Scott⁵, Ruilian Wu⁶, Rory Waterman², David E Morris⁷, Ping Yang⁸, Laura Gagliardi⁹, Jaqueline L Kiplinger¹⁰

Affiliations

¹ Chemistry Division, Los Alamos National Laboratory, Los Alamos, NM, USA.
² Department of Chemistry, University of Vermont, Burlington, VT, USA.
³ Department of Chemistry, University of Minnesota, Minneapolis, MN, USA.
⁴ Key Laboratory of Cluster Science of Ministry of Education, School of Chemistry and Engineering, Beijing Institute of Technology, Beijing, China.
⁵ Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, NM, USA.
⁶ Bioscience Division, Los Alamos National Laboratory, Los Alamos, NM, USA.
⁷ Chemistry Division, Los Alamos National Laboratory, Los Alamos, NM, USA. demorris@lanl.gov.
⁸ Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM, USA. pyang@lanl.gov.
⁹ Department of Chemistry, University of Minnesota, Minneapolis, MN, USA. gagliard@umn.edu.
¹⁰ Chemistry Division, Los Alamos National Laboratory, Los Alamos, NM, USA. kiplinger@lanl.gov.

^# Contributed equally.

PMID: 32103196
DOI: 10.1038/s41586-020-2004-7

Abstract

Aromaticity and antiaromaticity, as defined by Hückel's rule, are key ideas in organic chemistry, and are both exemplified in biphenylene^1-3-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 Biphenylene analogues in which one of the benzene rings has been replaced by a different (4n + 2) π-electron system have so far been associated only with organic compounds^4,5. 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.