4th EucheMs chemistry congress

Poster Session 1
s880
chem. Listy 106, s587–s1425 (2012)
Poster session 1 - Physical, theoretical chemistry
P - 0 0 4 2
APPLiCABiLity of MArCuS theory in ioniC
LiquidS. evidenCe froM eSr Line BroAdeninG
exPeriMentS
B. Sudy 1 , K. rASMuSSen 1 , G. GrAMPP 1
1 Graz University of Technology, Inst. of Physical and
Theoretical Chemistry, Graz, Austria
For more than half a century Marcus Theory [1] has been one
of the cornerstones in the understanding of outer-sphere electron
transfer reactions. The theory, together with many further
developments [2,3] , provides a thorough theoretical description of
the reaction energetics and kinetics and has been substantiated by
numerous experimental findings. Since Marcus Theory was
developed for polar liquids, using a dielectric continuum
approach, it is interesting to know to what extent it can be applied
to electron transfer in ionic liquids.
In the past, ESR line broadening experiments [4] on electron
self-exchange reactions in polar solvents have provided a wealth
of experimental information on Marcus Theory and thus suggest
themselves for similar studies in ionic liquids.
Several well-known self-exchange systems [5,6] have been
investigated in some common imidazolium based ionic liquids
using ESR spectroscopy at room temperature and at variable
temperatures or pressures. The experimental results, such as rate
constants, reorganization energies or solvent dynamic effects are
compared to their analogues from traditional solvents, as well as
to existing findings from literature, obtained using other
experimental methods.
references:
1. R. A. Marcus, J. Chem. Phys., 1956, 24, 966–978
2. M. Bixon and J. Jortner, Adv. Chem. Phys., 1999, 106,
35–208
3. Sutin, N., Prog. Inorg. Chem., 1983, 30, 441–498
4. G. Grampp, in Electron Paramagnetic Resonance,
Specialist Periodical Report, eds. B. C. Gilbert, N. M.
Atherton, M. J. Davies, RSC Cambridge, 1998, vol. 16
5. G. Grampp and W. Jaenicke, Ber. Bunsenges. Phys. Chem.,
1991, 95, 904–927
6. G. Grampp and K. Rasmussen, Phys. Chem. Chem. Phys.,
2002, 4, 5546–5549
Keywords: ESR; Electron Transfer; Ionic Liquids;
4 th EucheMs chemistry congress
P - 0 0 4 3
terMinAtion MeChAniSMS for PoLyoLefin
LivinG CAtALySiS At dft LeveL
v. viLLAni 1 , G. GiAMMArino 1
1 University of Basilicata, Chemistry, Potenza, Italy
Living polymerization is a hot topic in post-metallocene
catalysis. [1, 3] In fact, the synthesis of ultra-high molecular weight
polyethylene and block copolymers and the understanding of the
reaction mechanisms of the termination step are still challenging.
Fujita et al. [1] have been the first to highlight the living
behaviour of bis(phenoxyimine)Ti catalysts in the polymerization
of ethylene and propylene.
Mecking et al. [2] showed that the new bis(enolatoimine)
Ti catalyst, with ortho-fluorinated aryl groups, is able to achieve
the same living behaviour. Via NMR, the key role of the F-bond
interactions o-F···Ti in the suppression of the H -termination was
β
proposed.
In this communication, we investigate the mechanism of the
H -transfer in the termination reaction. The models used are
β
Mecking’s catalysts. DFT calculations were performed on a
parallel platform using GAUSSIAN09.
A procedure to simulate the termination reaction, usually
based on forcing the cleavage of Ti-C bond, has been developed.
α
The stationary structures have been localized and energy barriers
of activation determined. In transition states’ calculations, normal
mode analysis has been performed. The protective role of the
fluorine o-F···H and o-F···Ti bonds in the reactive species, and
repulsive o-F···o-F interactions destabilizing the transition states,
have been unraveled. An alternative H -transfer to the ligand, with
β
formation of an alkoxyimine, in the termination mechanism of
ortho-hydrogenated or -methylated non-living catalysts is
proposed.
references:
1. Terao, H.; Iwashita, A.; Matsukawa, N.; Ishii, S.; Mitani, M.;
Tanaka, H.; Nakano, T.; Fujita, T. ACS Catal. 2011, 1,
254-265.
2. Bryliakov, K. P.; Talsi, E. P.; Möller, H. M.; Baier, M. C.;
Mecking, S. Organometallics 2010, 29, 4428-4430.
3. Villani, V.; Giammarino, G. Macromolecules 2010, 43,
5917-5918.
Keywords: Hydrogen transfer; Density functional calculations;
Fluorinated ligands; Polymerization; Reaction mechanisms;
AUGUst 26–30, 2012, PrAGUE, cZEcH rEPUbLIc