Metal-acetylide bonding in ([eta][sup 5]-C[sub 5]H[sub 5])Fe(CO)[sub 2]C[triple bond]CR compounds. Measures of metal-d[pi]-acetylide-[pi] interactions from photoelectron spectroscopy

Journal Article · Wed Apr 21 00:00:00 EDT 1993 · Journal of the American Chemical Society; (United States)

DOI:https://doi.org/10.1021/ja00061a028· OSTI ID:6235437

Lichtenberger, D L; Renshaw, S K ^[1]; Bullock, R M ^[2]

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1. Univ. of Arizona, Tucson (United States)
2. Brookhaven National Lab., Upton, NY (United States)

Gas-phase He I and He II photoelectron spectroscopy is used to experimentally determine the bonding interactions of [eta][sup 1]-acetylide ligands in ([eta][sup 5]-C[sub 5]H[sub 5])Fe(CO)[sub 2]C[triple bond]CR compounds (R = H, [sup t]Bu, or phenyl). The spectra show a large amount of interaction between the metal d[pi] orbitals and the acetylide [pi] orbitals. Evidence for this is obtained from the splitting of metal-based ionization bands, from the shifts in Cp-based and acetylide-based ionizations, from the changes in ionization cross sections between the He I and He II spectra, and from vibrational fine structure in the metal-based ionizations. The data indicate that the predominant [pi] interactions between the acetylide ligands and the metal are filled/filled interactions between the occupied acetylide [pi] bonds and the occupied metal d[pi] orbitals. The electronic interactions of the C[triple bond]CR ligands with the metal are compared with those of CH[sub 3] (a primarily [sigma] donor ligand), halides ([pi] donor ligands), and C[triple bond]N (a weak [pi]* acceptor ligand), and are very similar to the interactions of the chloro ligand. Metal-to-acetylide-[pi]* back-bonding is extremely small in the acetylide compounds. Varying the acetylide substituent causes significant changes in the [sigma] and [pi] donor properties of the C[triple bond]CR ligand. Compared to C[triple bond]CH, the C[triple bond]C[sup t]Bu ligand is a stronger [sigma] donor ligand and also has a stronger filled/filled interaction between the metal d[pi] and acetylide [pi] orbitals. The electronic mixing with the C[triple bond]CPh ligand is even more extensive, since the metal d[pi] orbitals and the C[triple bond]C [pi] bonds are further mixed with the phenyl ring [pi] orbitals. 48 refs., 12 figs., 2 tabs.

• DOE Contract Number: FG02-86ER13501; AC02-76CH00016
• OSTI ID: 6235437
• Journal Information: Journal of the American Chemical Society; (United States), Journal Name: Journal of the American Chemical Society; (United States) Vol. 115:8; ISSN JACSAT; ISSN 0002-7863
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400102 -- Chemical & Spectral Procedures
400201* -- Chemical & Physicochemical Properties
DATA
ELECTRON SPECTROSCOPY
ELECTRONIC STRUCTURE
EXPERIMENTAL DATA
INFORMATION
IONIZATION
IRON COMPOUNDS
LIGANDS
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANOMETALLIC COMPOUNDS
PHOTOELECTRON SPECTROSCOPY
SPECTROSCOPY
TRANSITION ELEMENT COMPOUNDS