SMQ-V047 N-002_ligas_size.pdf - Journal of the Mexican Chemical ...

126 Rev. Soc. Quím. Méx. Vol. 47, Núm. 1 (2003) Valente Gómez-Benítez et al.
CH 2 directly coordinated to the P centers. It is noteworthy the
presence of a signal at 32.40 ppm which evidences the presence
of the coordinated olefin, the shift to higher field of this
particular signal clearly illustrates the protecting effects of the
aliphatic chain moiety in the case of the 1-octene adduct 4.
In both cases, the 31 P NMR spectra shows a unique signal
at 54.7 and 54.97 ppm for 3 and 4 respectively which is consistent
with a trans configuration for both phosphorus nuclei
in the two molecules. Elemental analysis are also consistent
with the proposed formulations. The FAB + -Mass spectra of 3
exhibits a peak at 585 M/z [M + -H 2 C=CH 2 ] corresponding to
the loss of the ethylene molecule while that of 4 shows the
molecular ion at [M + = 698 M/z].
Both complexes have been exposed to catalytic conditions
where the reaction temperature reaches 200 °C, at this
temperature the complex containing ethylene, releases the ethylene
molecule which makes this complex an excellent candidate
for further studies oriented to the possible functionalization
of this molecule, however the complex containing the 1-
octene it is resistant even at this temperatures, therefore it can
be conclude that it is precisely this stability the problem
(product inhibition) we have to go against in order to optimize
the present system for the dehydrogenation process, other
alternatives will involve the design of new ligands where electronic
and steric factors could be tuned in such way that the
elimination of the alkene molecule could be carried out easier
and faster. Efforts aimed to achieve this goals are currently
under investigation in our laboratory.
Acknowledgements
V. G.-B. would like to thank CONACyT and DGAPA for
financial support. We would like to thank Chem. Eng. Luis
Velasco Ibarra and M. Sc. Francisco Javier Perez Flores for
their invaluable help in the running of the FAB-Mass Spectra.
The support of this research by CONACyT (J41206-Q) and
DGAPA-UNAM (IN116001) is gratefully acknowledged.
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