Vibrational characterization of multiply metal-metal bonded osmium, molybdenum, and rhenium porphyrin dimers

Journal Article · Wed Dec 06 00:00:00 EST 1989 · Journal of the American Chemical Society; (USA)

DOI:https://doi.org/10.1021/ja00207a012· OSTI ID:7157110

Tait, C D; Sattelberger, A P; Woodruff, W H ^[1]; Garner, J M; Collman, J P ^[2]

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1. Los Alamos National Lab., NM (USA)
2. Stanford Univ., CA (USA)

The resonance Raman (RR) scattering and infrared (IR) absorption spectra of ((M(OEP)){sub 2}){sup n+} complexes (OEP = 2,3,7,8,12,13,17,18-octaethylporphyrin dianion; M = Os (n = 0-2), Re (n = 0-2), and Mo (n=0)) are reported. Resonance Raman studies reveal the Os-Os stretch to increase in frequency upon oxidation (233 cm{sup {minus}1} (n = 0), 254 cm{sup {minus}1} (n = 1), and 266 cm{sup {minus}1} (n = 2)), consistent with the removal of electrons from {pi}* metal-metal antibonding orbitals. The Mo-Mo stretch was also observed spectroscopically, producing a RR peak at 341 cm{sup {minus}1}, while the Re-Re stretch in ((Re(OEP)){sub 2}){sup 1+} was observed at 290 cm{sup {minus}1}. The corresponding metal-metal bond distances estimated from these stretching frequencies are 2.39, 2.31, and 2.27 {angstrom} for the osmium oxidation series, 2.23 {angstrom} for the molybdenum dimer, and 2.20 {angstrom} for the rhenium dimer. The porphyrin-centered vibrational modes (both RR and IR active) for the three osmium complexes are essentially independent of oxidation state, consistent with oxidation of metal-metal antibonding electrons. Little {pi} back-bonding between the metal and porphyrin macrocycle is suggested from porphyrin RR indicator modes, which are sensitive to {pi} electron density. Moreover, the porphyrin core size (center to nitrogen distance) is estimated from core size marker vibrations to be ca. 2.04 {angstrom} for all of the complexes studied. Finally, no vibrational evidence for ground-state intradimer coupling between the {pi} orbitals of the porphyrin rings is found.

• OSTI ID: 7157110
• Journal Information: Journal of the American Chemical Society; (USA), Vol. 111:25; ISSN 0002-7863
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
36 MATERIALS SCIENCE
PORPHYRINS
VIBRATIONAL STATES
DATA ANALYSIS
DIMERS
EXPERIMENTAL DATA
INFRARED SPECTRA
MEASURING INSTRUMENTS
MEASURING METHODS
MOLYBDENUM
OSMIUM
RAMAN SPECTRA
RHENIUM
CARBOXYLIC ACIDS
DATA
ELEMENTS
ENERGY LEVELS
EXCITED STATES
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
INFORMATION
METALS
NUMERICAL DATA
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PLATINUM METALS
SPECTRA
TRANSITION ELEMENTS
400000* - Chemistry
400201 - Chemical & Physicochemical Properties
400500 - Photochemistry
360104 - Metals & Alloys- Physical Properties