Isomerization of the osmium-tellurium cluster Osβ(π-TeR)β(CO)ββ: a kinetic and computational study Page: 7,161
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Dalton Transactions
drying agent under argon before use. Infrared (IR) spectra were
recorded in a solution IR cell with NaCl windows and a path
length of 0.1 mm, at a resolution of 2 cm-1. 1H NMR spectra
were recorded on a Bruker AV300 at 300 MHz while variable
temperature 1H NMR spectra were recorded on a JEOL ECA
400 at 400 MHz, referenced to the residual proton resonance
of the solvent. Compounds 1 and 2 were synthesized according
to literature methods.2,9
Kinetics measurements
Cluster 3-Tol-p (8 mg, 0.0062 mmol) was dissolved in C6D6 and
1,3,5-trimethoxybenzene was added as an internal standard.
The solutions were placed in an oil bath set at various temp-
eratures (25 oC, 35 oC, 55 oC or 75 oC) and the conversion of
3-Tol-p was monitored via 1H NMR spectroscopy. The mass
balance was checked by plotting (I3 + I4) against the reaction
time (t), where I3 and 14 are the scaled, integrated intensities
of 3-Tol-p and 4-Tol-p, respectively. The rate constant (k) at
3
each temperature was obtained from a plot of ln
I3 + I4
against t. An Eyring plot was then obtained to obtain AHi and AS.
X-ray crystal structure determination
A crystal of 4-Tol-p was mounted on a quartz fiber. X-ray data
were collected on a Bruker AXS APEX system, using Mo Kx
radiation, with the SMART suite of programs.10 The data were
processed and corrected for Lorentz and polarization effects
with SAINT,11 and for absorption effects with SADABS.12 Struc-
tural solution and refinement were carried out with the
SHELXTL suite of programs.13 The structure was solved by
direct methods, followed by difference maps to complete the
structure for all the non-hydrogen atoms. The structure was
found to be a racemic twin. Organic hydrogen atoms were
placed in the calculated positions and refined with a riding
model. All non-hydrogen atoms were generally given aniso-
tropic displacement parameters in the final model.
Computational studies
All DFT calculations were carried out with the Gaussian 09
package of programs,14 using M06 as the DFT functional.15
The osmium and tellurium atoms were described with the
Stuttgart-Dresden effective core potential and SDD basis set,16
and the 6-31G(d') basis set was employed for all the remaining
atoms.17
All the reported geometries were fully optimized, and
analytical second derivatives were evaluated at each stationary
point to verify whether the geometry was an energy minimum
(positive eigenvalues) or a transition structure (one negative
eigenvalue). Unscaled vibrational frequencies were used to
make zero-point and thermal corrections to the electronic
energies. The resulting free energies are reported in kJ mol-1
relative to the specified standard. All transition states on the
potential energy surface were evaluated by intrinsic reaction
coordinate (IRC) calculations, in order to establish the reactant
and product species associated with each transition-state struc-ture. The natural charges and Wiberg bond indices were com-
puted using Weinhold's natural bond orbital (NBO) program,
as executed by Gaussian 09.18 Geometry-optimized structures
have been drawn with the JIMP2 molecular visualization and
manipulation program.19
Acknowledgements
This work was supported by Nanyang Technological University,
the Ministry of Education (Research Grant No. M4011158), and
the Robert A. Welch Foundation (Grant B-1093-MGR). Compu-
tational resources through the High-Performance Computing
Services and CASCaM at the University of North Texas are
acknowledged. We thank Dr Rakesh Ganguly for assistance
with the X-ray crystallographic data collection and processing
and Prof. Michael B. Hall (TAMU) for providing us a copy of
his JIMP2 program, which was used to prepare the geometry-
optimized structures reported here.
Notes and references
1 Some kinetic studies carried out on osmium clusters:
(a) W. H. Watson, B. Poola and M. G. Richmond,
J. Organomet. Chem., 2006, 691, 4676-4685; (b) L. J. Pereira
and W. K. Leong, J. Organomet. Chem., 2006, 691, 1941-
1944; (c) J. Cooke and J. Takats, Organometallics, 1995, 14,
698-702; (d) J. B. Keister, U. Frey, D. Zbinden and
A. E. Merbach, Organometallics, 1991, 10, 1497-1501;
(e) L. J. Farrugia, Organometallics, 1989, 8, 2410-2417;
(f) S. J. Heyes, C. M. Dobson, M. A. Gallop, B. F. G. Johnson
and J. Lewis, Inorg. Chem., 1991, 30, 3850-3856;
(g) R. D. Adams, M. P. Pompeo and W. Wu, Inorg. Chem.,
1991, 30, 2899-2905.
2 J. Zhang and W. K. Leong, J. Chem. Soc., Dalton Trans.,
2000, 1249.
3 Reports on osmium-sulfur, selenium, and antimony
clusters: (a) O. Reyes-L6pez, S. A. Sanchez-Ruiz, A. Flores-
Parra, M. A. Leyva, R. J. Alvarez-Mendez, A. Vela and
M. J. Rosales-Hoz, J. Organomet. Chem., 2014, 772-773,
248-257; (b) R. D. Adams and J. A. Belinski, Organometal-
lics, 1992, 11, 2488-2493; (c) B. F. G. Johnson, J. Lewis,
P. G. Lodge, P. R. Raithby, K. Henrick and M. McPartlin, J.
Chem. Soc., Chem. Commun., 1979, 719-720; (d) J. Arce,
A. Karam, Y. De Sanctis, R. Machado, M. V. Capparelli and
J. Manzur, Inorg. Chim. Acta, 1997, 254, 119-130; (e) J. Arce,
R. Machado, C. Rivas, Y. De Sanctis and A. J. Deeming,
J. Organomet. Chem., 1991, 419, 63-75.
4 (a) E. C. Morrison, W. K. Leong and J. Tan, J. Cluster Sci.,
2007, 18, 753-763; (b) J. C. Sarker, K. M. Uddin,
M. S. Rahman, S. Ghosh, T. A. Siddiquee, D. A. Tocher,
M. G. Richmond, G. Hogarth and S. E. Kabir, Inorg. Chim.
Acta, 2014, 409, 320-329; (c) L. Yang, V. N. Nesterov,
X. Wang and M. G. Richmond, J. Cluster Sci., 2014, 26,
93-109.This journal is The Royal Society of Chemistry 2016
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Paper
Dalton Trans., 2016, 45, 7158-7162 1 7161
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Shim, E. K. S.; Leong, W. K.; Li, Y. -Z. & Richmond, Michael G. Isomerization of the osmium-tellurium cluster Osβ(π-TeR)β(CO)ββ: a kinetic and computational study, article, March 8, 2016; London, United Kingdom. (https://digital.library.unt.edu/ark:/67531/metadc990951/m1/4/: accessed April 19, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT College of Arts and Sciences.