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 C3ν 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.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Organic Chemistry
- Inorganic Chemistry