Abstract
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.
| Original language | English |
|---|---|
| Pages (from-to) | 401-407 |
| Number of pages | 7 |
| Journal | Organometallics |
| Volume | 20 |
| Issue number | 3 |
| DOIs | |
| Publication status | Published - Feb 5 2001 |
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ASJC Scopus subject areas
- Inorganic Chemistry
- Organic Chemistry
Cite this
Solvent study of the kinetics of molybdenum radical self-termination. / Linehan, John; Yonker, Clement R.; Addleman, R. Shane; Autrey, S. Thomas; Bays, J. Timothy; Bitterwolf, Thomas E.; Daschbach, John L.
In: Organometallics, Vol. 20, No. 3, 05.02.2001, p. 401-407.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Solvent study of the kinetics of molybdenum radical self-termination
AU - Linehan, John
AU - Yonker, Clement R.
AU - Addleman, R. Shane
AU - Autrey, S. Thomas
AU - Bays, J. Timothy
AU - Bitterwolf, Thomas E.
AU - Daschbach, John L.
PY - 2001/2/5
Y1 - 2001/2/5
N2 - 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.
AB - 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.
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U2 - 10.1021/om000724j
DO - 10.1021/om000724j
M3 - Article
AN - SCOPUS:0035809290
VL - 20
SP - 401
EP - 407
JO - Organometallics
JF - Organometallics
SN - 0276-7333
IS - 3
ER -