Vibrational Study of (η⁵-Cyclopentadienyl)metal Complexes

Abstract

Raman and infrared spectral data on the vibrational modes of the M-(η 5 -C 5 H 5 ) unit have been collected and the fundamental assignments revisited. Complexes belonging to the metallocene series M(η 5 -C 5 H 5 ) and the cyclopentadienide salts [η 5 -C 5 H 5 -][M + ] have been studied, together with some monometallic (η 5 -C 5 H 5 )ML n and bimetallic (η 5 -C 5 H 5 ) 2 M 2 L 2n compounds. Comparison of the spectra shows a common vibrational pattern of the intraring modes, with minor variations in frequency and intensity, which allows the establishment of a vibrational fingerprint of general validity. Raman spectra give rise to a firm assignment of the skeletal metal-ring modes; a correlation is noted between the metal-ring stretch force constant and the metal-carbon distance. The approximate CH out-of-plane force constants vary considerably and presumably reflect different H-ring electrostatic repulsions.

The vibrational spectrum of solid ferrocene by inelastic neutron scattering

“…4͒. Here the two C 5 H 5 rings oscillate in plane, but out of phase with each other with frequency 6 around the equilibrium position at ϭ9°͑cf. Fig.…”

“…[1][2][3][4][5][6][7][8][9][10] The interest lies in the unusual symmetric form of ferrocene ͑two identical cyclopentadienyl C 5 H 5 rings on both sides of the Fe atom͒ while it is also the stablest member of the metallocene group, which in general has important catalytic properties. The vibrational frequencies of ferrocene have been calculated theoretically before and verified experimentally by Raman and infrared ͑IR͒ spectroscopy.…”

Inclusion of molybdenocene dichloride (Cp2MoCl2) in 2-hydroxypropyl- and trimethyl-β-cyclodextrin: Structural and biological properties

“…Blue-shifts of m(CH) and p(CH) modes in similar metal-cyclopentadienyl complexes have been previously associated with an increase in the covalency of the Cp-M bond [28]. However, more recent vibrational studies discard this hypothesis in favour of an increase in the electron density in the Cp ring [29]. Several low wavenumber bands of 1 are identified in the Raman spectra of 1a and 1b, assigned to Mo-Cp and Mo-Cl modes (Table 1).…”

Inclusion compounds of cystostatic active (C5H5)2VCl2 and (CH3C5H4)2VCl2 with α-, β- and γ-cyclodextrines: Synthesis, EPR study and microbiological behavior toward Escherichia coli

“…Particularly, the presence of η 5 [20].The vibra-tion spectra, however, does not give any information about inclusion. This information was obtained from anisotropic EPR spectra.…”