Síntesis regioselectiva de ligandos N-alquil-3,5-pirazol y estudio de su reactividad con Pd(II) y Pt(II). Complejos de Pd(II) como nuevos catalizadores para la reacción de Heck
In this Thesis new N-alkyl-3,5-pyrazole and N-hidroxialkyl-3,5-pyrazole derived ligands have been synthesized. These ligands have been obtained by reaction between 3,5-pyrazole derived ligands and the appropriate haloalkane in toluene or THF using NaOEt or NaH as base. When the precursor ligand has a pyridyl substituent the alkylation reaction presents a large regioselectivity. Theoretical calculations have been carried out to rationalize the experimental observations, showing that regioselectivity is governed by the formation of Na+-pyrazolide chelate complexes.
It is also been studied the reactivity of some of these ligands with different products of palladium and platinum(II).
Reactions of the monodentated N-alkyl-3,5-pyrazole derived ligands synthesized in this work with chlorocomplexes gave complexes trans-[MCl2(L)2]. The presence of one or two isomers in solution (syn or anti) is due to a hindered rotation around the Pd-N bond, controlled by steric factors coming from the size of alkyl groups and the nature of the metal.
On the other hand, the reaction between N-alkyl-3-pyridil-5-sustituted-pyrazole ligands and chlorocomplexes in 1:1 and 2:1 proportion resulted in the formation complexes of formula cis-[MCl2(L)] or [M(L)2](X)2 (X = BF4 or BPPh4).
Treatment of cis-[PdCl2(L)] (L = N-alkyl-3-pyridil-5-sustituted-pyrazole ligands) with pyridine (py) or triphenylphosphine (PPh3) produced new complexes by substitution of chloride by the corresponding monodentate ligand (py or PPh3). However, the complexes whose formula are cis-[PdCl2(L)] have been proved like catalyst in the Heck reaction.
Finally, allylpalladium [Pd(?3-C3H5)(L)](BF4) complexes with N-alkyl-3-pyridil-5-sustituted-pyrazole ligands were synthesised from the appropiate piridinylpyrazole ligand and ?3-allylpalladium chloride dimer in the presence of AgBF4. Also, it was studied the apparent allyl rotation that is observed as Hsyn-Hsyn and Hanti-Hanti interconversions.
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Advisor:Ros Badosa, Josep; Pons Picart, Josefina
School:Universitat Autónoma de Barcelona
Source Type:Master's Thesis
Keywords:403 departament de quimica
Date of Publication:12/19/2006