Type of Publication: | Journal article |
Author: | Selg, Peter; Brintzinger, Hans-Herbert; Schultz, Madeleine; Andersen, Richard A. |
Year of publication: | 2002 |
Published in: | Organometallics ; 21 (2002), 15. - pp. 3100-3107. - ISSN 0276-7333. - eISSN 1520-6041 |
DOI (citable link): | https://dx.doi.org/10.1021/om011045r |
Summary: |
The reaction of CO with the alkaline-earth decamethylmetallocenes Cp*2MII, where MII is Mg, Ca, Sr, or Ba, and the bivalent lanthanide decamethylmetallocenes, where MII is Sm, Eu, or Yb, have been studied in toluene or methylcyclohexane solution in a high-pressure infrared cell. In all cases, except for Mg and Ba, the monocarbonyl complex Cp*2MCO is observed to form under CO pressure. The CO stretching frequencies for Cp*2CaCO (2158 cm-1), Cp*2SrCO (2159 cm-1), Cp*2SmCO (2153 cm-1), and Cp*2EuCO (2150 cm-1) are greater than that of free CO (2134 cm-1 in toluene or methylcyclohexane). In contrast, Cp*2YbCO has νCO 2114 cm-1, below that of free CO. This 1:1 complex is formed at low CO pressure (<2 bar); at higher CO pressures the 1:2 adduct Cp*2Yb(CO)2 with an even lower νCO value of 2072 cm-1 predominates. Equilibrium constants were determined as a function of pressure and temperature for the equilibria Cp*2MII(solv) + nCO(gas or solv) Cp*2MII(CO)n(solv), with MII = Ca, Eu, Yb. The thermodynamic constants ΔH°, ΔS°, and ΔG° for the formation of each species, extracted from the changes in the intensity of the corresponding ΙR absorption bands, indicate weak MII−CO binding. Models to account for the bonding in these metallocene CO adducts are discussed.
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Subject (DDC): | 540 Chemistry |
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SELG, Peter, Hans-Herbert BRINTZINGER, Madeleine SCHULTZ, Richard A. ANDERSEN, 2002. Solution infrared spectroscopic studies on equilibrium reactions of CO with the decamethylmetallocenes Cp*2MII, where MII = Mg, Ca, Sr, Ba, Sm, Eu, Yb. In: Organometallics. 21(15), pp. 3100-3107. ISSN 0276-7333. eISSN 1520-6041. Available under: doi: 10.1021/om011045r
@article{Selg2002Solut-23728, title={Solution infrared spectroscopic studies on equilibrium reactions of CO with the decamethylmetallocenes Cp*2MII, where MII = Mg, Ca, Sr, Ba, Sm, Eu, Yb}, year={2002}, doi={10.1021/om011045r}, number={15}, volume={21}, issn={0276-7333}, journal={Organometallics}, pages={3100--3107}, author={Selg, Peter and Brintzinger, Hans-Herbert and Schultz, Madeleine and Andersen, Richard A.} }