Electron Distribution and Bonding in η3-Cyclopropenyl-Metal Complexes

Dennis L. Lichtenberger, Martin L. Hoppe, Lalitha Subramanian, Edward M. Kober, Russell P. Hughes, John L. Hubbard, David S. Tucker

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27 Scopus citations


The synthesis of (η3-C3R3)Ir(CO)3 and He I and He II photoelectron spectra of (η3-C3R3)Co(CO)3, (η3-C3R3)Ir(CO)3, and (η3-C3R3)Fe(CO)2(NO) (where R = tert-butyl) are reported. The shifts and splittings in ionization energies with the metal and ligand perturbations in this series, the changes in ionization peak areas as a function of the excitation energy, and Fenske-Hall molecular orbital calculations assist in the assignment and interpretation of the spectra. The cobalt complex reveals three peaks in the low ionization energy region that are primarily metal-based, consistent with the two states of e symmetry and one state of a1 symmetry from the five d orbitals of a formally d10 metal in C symmetry. The spectrum of the iridium complex has five peaks in this region due to large spin-orbit coupling that splits the e symmetry ionizations. The doubly degenerate peaks of the cobalt complex are also expected to be split in the photoelectron spectrum of the iron-nitrosyl complex due to the lowering to Cs symmetry. Only four distinct peaks are seen for the iron-nitrosyl complex, with two ionization bands at higher energy being merged in a broad envelope. The ionization cross-sections indicate that the η3-bound C3R3 ligand in these complexes is best described formally as a cation with a large amount of mixing and backbonding from the metal dπ orbitals to the eπ* orbitals of the cyclopropenyl ring. This is compared to the NO+ ligand.

Original languageEnglish (US)
Pages (from-to)2025-2031
Number of pages7
Issue number6
StatePublished - 1993

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Inorganic Chemistry


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