Gas-Phase Iron Tricarbonyl Cyclooctatetraene Exhibits a "Rigid-Rotor" Microwave Spectrum

Stephen G Kukolich, S. M. Breckenridge-Estes, S. M. Sickafoose

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

The microwave rotational spectrum of (μ4-C8H8) Fe(CO)3 was measured in the 4-12 GHz range using a pulsed- beam, Fourier transform spectrometer system. Nearly all strong transitions can be fit using a near-rigid-rotor model with very small centrifugal distortion terms. These results indicate that this complex has a fairly rigid structure in the gas phase, with no observed evidence for fluxional behavior or internal rotation on the microwave time scale (τ < 10-4 s). These gas-phase observations initially appeared to be in sharp contrast to the solution NMR studies, where this complex is observed to be a "ring whizzer" with cyclic 1,2 carbon shifts. Further analysis indicates these two sets of measurements are compatible since, with an intermediate level barrier to internal motion (V > 500 cm-1), the structure would appear rigid on the microwave time scale, yet could appear quite fluxional on the much longer NMR time scale. The rotational constants are A = 825.2559(2), B = 510.5149- (1), and C = 462.5246(1) MHz. Centrifugal distortion constants are ΔJ = 0.0146(5), ΔJK = 0.015(3), ΔK = 0.049(4), δJ = 0.0034(3), and δK = -0.092(6) kHz. The measured rotational constants all agree with those calculated from the X-ray structure to within 0.3%. The excellent agreement between the rotational constants makes it very likely that the solid-state and gas-phase structures are nearly identical.

Original languageEnglish (US)
Pages (from-to)4916-4918
Number of pages3
JournalInorganic Chemistry
Volume36
Issue number22
StatePublished - 1997

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Rigid rotors
rigid rotors
microwave spectra
Iron
Gases
Microwaves
vapor phases
iron
Rigid structures
Carbon Monoxide
Phase structure
microwaves
Spectrometers
Fourier transforms
rotational spectra
rigid structures
Nuclear magnetic resonance
X rays
spectrometers
solid state

ASJC Scopus subject areas

  • Inorganic Chemistry

Cite this

Gas-Phase Iron Tricarbonyl Cyclooctatetraene Exhibits a "Rigid-Rotor" Microwave Spectrum. / Kukolich, Stephen G; Breckenridge-Estes, S. M.; Sickafoose, S. M.

In: Inorganic Chemistry, Vol. 36, No. 22, 1997, p. 4916-4918.

Research output: Contribution to journalArticle

Kukolich, SG, Breckenridge-Estes, SM & Sickafoose, SM 1997, 'Gas-Phase Iron Tricarbonyl Cyclooctatetraene Exhibits a "Rigid-Rotor" Microwave Spectrum', Inorganic Chemistry, vol. 36, no. 22, pp. 4916-4918.
Kukolich, Stephen G ; Breckenridge-Estes, S. M. ; Sickafoose, S. M. / Gas-Phase Iron Tricarbonyl Cyclooctatetraene Exhibits a "Rigid-Rotor" Microwave Spectrum. In: Inorganic Chemistry. 1997 ; Vol. 36, No. 22. pp. 4916-4918.
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