Preparació i caracterització de complexos de ruteni amb aplicació a la catàlisi d'acoblament d'alcohols en condicions tèrmiques i fotoactivades

Abstract

Throughout this study, the synthesis of a set of ruthenium complexes has been carried

out with the aim of coordinating different types of ruthenium ligands. The aim of these

synthesised complexes is to use them for the catalysis of alcohol assembly reactions.

Firstly, the ligand bpea (N,N-bis(2-pyridylmethyl)ethylamine) and the complex [1],

[RuCl2(dmso)4], have been synthesised and used to obtain the complex [2] (cis,fac-

[RuCl2(bpea)(dmso)]). The complex [3], [RuCl3(bpea)], . has been prepared from RuCl3

and the same bpea ligand. A second ligand, 3-methyl-1-(pyridin-2-yl)-1H-imidazol-3-

yum-hexafluorophosphate (HCb-Me(PF6)), has also been synthesised and reacted with

complex [3] to give complex [4], (trans,fac-[RuCl(Cb-Me)(bpea)]).

The bpea and HCb-Me(PF6) ligands have been characterised by 1H-RMN, while other

spectroscopic and electrochemical techniques such as UV-Visible and cyclic

voltammetry have been used for the [1]-[4] complexes. In the case of complexes [2]

and [4], the analysis by 1H-RMN has allowed us to determine that they are obtained as

single isomers, cis,fac- and trans,fac- respectively.

The complexes [2] and [4] show, in the UV-vis spectra, charge transfer metal-lligand

(TCML) bands, as well as intralligand π-π* transitions. An effect of the dmso ligands on

the energy of the TCML transitions can be observed, which are more energetic for the

complex [2], which contains this π-acceptor ligand.Cyclic voltammetry of the [2]-[4]

complexes shows reversible waves corresponding to the RuIII/RuII redox pair, which

has a particularly low E1/2 potential value in the case of the [3] complex, as it has three

chloride ligands in the coordination environment.

Catalysis tests on the alcohol assembly reaction have been performed with the

complexes [2] and [4] under thermal (80ºC) and also photoactivated (applying visible

light) conditions. The quantification of the catalysis products has been performed by

gas chromatography with FID detector and, in the case of complex [4], some evolution

and quantification controls have also been performed by 1H-RMN. Conversion and

selectivity values have been obtained that allow us to see the efficiency of the catalysts

over 1, 3, 5 and 7 days, and it has been observed that, while the complex [2] shows

practically no catalytic activity, the complex [4] proves to be efficient in the tests carried

out under temperature