Reversible Sigma C–C Bond Formation Between Phenanthroline Ligands Activated by (C₅Me ₅)₂Yb

Journal Article · Thu May 22 04:00:00 EDT 2014 · Journal of the American Chemical Society

DOI:https://doi.org/10.1021/ja502271q· OSTI ID:1469132

Nocton, Gregory ^[1]; Lukens, Wayne W. ^[2]; Booth, Corwin H. ^[2]; Rozenel, Sergio S. ^[3]; Medling, Scott A. ^[2]; Maron, Laurent ^[4]; Andersen, Richard A. ^[3]

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1. Ecole Polytechnique, Palaiseau (France). Lab. de Chimie Moléculaire, CNRS; Univ. of California, Berkeley, CA (United States). Dept. of Chemistry
2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Chemical Sciences Division
3. Univ. of California, Berkeley, CA (United States). Dept. of Chemistry; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Chemical Sciences Division
4. Univ. de Toulouse-CNRS, Toulouse (France)

The electronic structure and associated magnetic properties of the 1,10-phenanthroline adducts of Cp*₂Yb are dramatically different from those of the 2,2'-bipyridine adducts. The monomeric phenanthroline adducts are ground state triplets that are based upon trivalent Yb(III), f¹³, and (phen•– ) that are only weakly exchange coupled, which is in contrast to the bipyridine adducts whose ground states are multiconfigurational, open-shell singlets in which ytterbium is intermediate valent ( J. Am. Chem. Soc 2009, 131, 6480; J. Am. Chem. Soc 2010, 132, 17537). The origin of these different physical properties is traced to the number and symmetry of the LUMO and LUMO+1 of the heterocyclic diimine ligands. The bipy•– has only one π*₁ orbital of b₁ symmetry of accessible energy, but phen•– has two π* orbitals of b₁ and a₂ symmetry that are energetically accessible. The carbon pπ-orbitals have different nodal properties and coefficients and their energies, and therefore their populations change depending on the position and number of methyl substitutions on the ring. A chemical ramification of the change in electronic structure is that Cp*₂Yb(phen) is a dimer when crystallized from toluene solution, but a monomer when sublimed at 180–190 °C. When 3,8-Me2phenanthroline is used, the adduct Cp*₂Yb(3,8-Me₂phen) exists in the solution in a dimer–monomer equilibrium in which ΔG is near zero. The adducts with 3-Me, 4-Me, 5-Me, 3,8-Me₂, and 5,6-Me₂-phenanthroline are isolated and characterized by solid state X-ray crystallography, magnetic susceptibility and L_III-edge XANES spectroscopy as a function of temperature and variable-temperature ¹H NMR spectroscopy.

• Research Organization: Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Chemical Sciences, Geosciences & Biosciences Division; CNRS; Ecole Polytechnique, Palaiseau (France)
• DOE Contract Number: AC02-05CH11231
• OSTI ID: 1469132
• Report Number(s): LBNL--182091; ir:182091
• Journal Information: Journal of the American Chemical Society, Journal Name: Journal of the American Chemical Society Journal Issue: 24 Vol. 136; ISSN 0002-7863
• Publisher: American Chemical Society (ACS)
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY