Vibrational fine structure in the valence ionizations of transition-metal hexacarbonyls: new experimental indication of metal-to-carbonyl. pi. bonding

Journal Article · Wed Apr 21 04:00:00 EST 1982 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00372a008· OSTI ID:5041582

Hubbard, J L; Lichtenberger, D L

The first observations of metal-carbon vibrational structure in photoionization bands are reported. Attention is focused on the predominantly metal d ionizations of M(CO)/sub 6/ (M = Cr, Mo, and W), and the methods for obtaining high resolution and very high signal-to-noise He I ionization data are detailed. The /sup 2/T/sub 2g/ ionization band of Cr(CO)/sub 6/ and the spin-orbit split /sup 2/E'' and /sup 2/U' bands of W(CO)/sub 6/ show distinct vibrational progressions which correspond to the totally symmetric (a/sub 1g/) metal-carbon stretching mode in the positive ion states. The metal-carbon stretching frequencies are found to be significantly less in the positive ion states than in the ground states, indicating a reduction of metal-carbon bond order upon the loss of a t/sub 2g/ electron. Evaluation of the vibrational progressions shows that the metal-carbon bond length increases on the order of 0.10 A upon t/sub 2g/ ionization in the case of W(CO)/sub 6/ and about 0.14 A in the case of Cr(CO)/sub 6/. In addition, the beginning of a short progression in the a/sub 1g/ carbon-oxygen stretching mode is observed in the Mo(CO)/sub 6/ spectrum and is clearly seen in the W(CO)/sub 6/ spectrum. All of these observations show that removal of an electron from the predominantly metal t/sub 2g/ orbitals, which are strictly ..pi.. symmetry with respect to the carbonyls, substantially weakens the metal-to-carbonyl bond. 9 figures, 2 tables.

• Research Organization: Univ. of Arizona, Tucson
• OSTI ID: 5041582
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 104:8; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
400301 -- Organic Chemistry-- Chemical & Physicochemical Properties-- (-1987)
CHEMICAL REACTIONS
CHROMIUM COMPOUNDS
DATA
DECOMPOSITION
ELECTRON SPECTROSCOPY
ENERGY LEVELS
EXCITED STATES
EXPERIMENTAL DATA
FOURIER ANALYSIS
FREQUENCY DEPENDENCE
HYPERFINE STRUCTURE
INFORMATION
IONIZATION
MOLYBDENUM COMPOUNDS
NUMERICAL DATA
PHOTOCHEMICAL REACTIONS
PHOTOELECTRON SPECTROSCOPY
PHOTOIONIZATION
PHOTOLYSIS
SPECTROSCOPY
TRANSITION ELEMENT COMPOUNDS
TUNGSTEN COMPOUNDS
VIBRATIONAL STATES