| Autor: |
Linehan, J. C., Yonker, C. R., Addleman, R. S., Autrey, S. T., Bays, J. T., Bitterwolf, T. E., Daschbach, J. L. |
| Zdroj: |
Organometallics; February 2001, Vol. 20 Issue: 3 p401-407, 7p |
| Abstrakt: |
The kinetics of (n-butylCp)Mo(CO)3 (n-butylCp is n-butyl-η5-cyclopentadienyl) radical self-termination to form a nonequilibrium mixture of trans- and gauche-[(n-butylCp)Mo(CO)3]2 and the kinetics of the gauche-to-trans isomerization have been determined in the liquid solvents n-heptane, tetrahydrofuran, xenon (350 bar), and CO2 (350 bar) at 283 K by step-scan FTIR spectroscopy. The overall rate constant for the disappearance, 2kR, of the (n-butylCp)Mo(CO)3 radical increases with decreasing solvent viscosity as expected, except in CO2, which is anomalously slower. The slower overall termination rate in liquid CO2 is consistent with the formation of a transient molybdenum radical−CO2 complex. The observed overall rate constants for (n-butylCp)Mo(CO)3 self-termination, 2kR, are (7.9 ± 0.5) × 109 M-1 s-1 in xenon; (3.2 ± 0.5) × 109 M-1 s-1 in heptane; (2.2 ± 0.8) × 109 M-1 s-1 in THF; and (1.7 ± 0.5) × 109 M-1 s-1 in CO2. The first determinations of the radical self-termination-to-gauche rate constants, kG, are presented. The values of kG are much slower than the corresponding recombination to trans, kT, reflecting a steric contribution to the rate. The rate of isomerization (rotation about the molydenum−molybdenum bond) from gauche to trans is unaffected by the solvent and is 3 times faster than the reported isomerization rate for the nonsubstituted [CpMo(CO)3]2 molecule. |
| Databáze: |
Supplemental Index |
| Externí odkaz: |
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