Synthesis, reactivity and applications in organic synthesis of fluoroalkylated organometallic complexes of rhodium, iridium and gold

Resumen

Owing to the important applications of fluorinated organic compounds, there is a demand of synthetic methods to selectively introduce perfluoroalkyl substituents in organic substrates. Despite the recent advances in this field, the metal-mediated or -catalyzed formation of C-perfluoroalkyl bonds is still challenging because of the poor reactivity of perfluoroalkyl metal complexes. In this context, the general aim of this work is to increase the knowledge of the chemistry of perfluoroalkyl metal complexes and metal-mediated perfluoroalkylation reactions. In particular, our goals were: (a) To study new alkene perfluoroalkylation reactions in the coordination sphere of Rh or Ir complexes; (b) to synthesize and study the reactivity of new types of Au(I) and Au(III) trifluoromethyl complexes. In addition, we aimed to synthesize Au(III) pincer complexes with an intense photoluminescence which could be sensitive to the chemical environment. The first chapter of the thesis reports the reactions of complexes of the type [M(Cp*)(ethene)L] (M = Rh, Ir; L = ethene, triphenilphosphine o trimethyphosphine) with primary, secondary and tertiary iodoperfluoroalkanes. These reactions led to perfluoroalkylation of the coordinated ethene to give complexes of the type [M(Cp*)(CH2CH2-perfluoroalkyl)(I)L]. Depending on the ancillary ligand of the starting complexes and the iodoperfluoroalkane, these reactions proceed by attack of perfluoroalkyl anions or radicals to the coordinated ethene. The reactivity of the resulting complexes was studied and derivatives containing phosphine, CO and isocyanide ligands were prepared. Remarkably, perfluoroalkylethenes were formed by beta-elimination reactions after removing an iodide ligand by reaction with silver(I) triflate. The intermediate Ir(III) hydrido-alkene complexes were isolated and studied. In the reactions of these complexes with triphenylphosphine a C-H activation reaction was observed that led to a cyclometalated Ir(III) complex and fluoroalkanes of the type CH3CH2-perfluoroalkyl. Complexes [M(Cp*)(ethene)L] and their perfluoroalkylated M(III) derivatives (M = Rh, Ir) are able to initiate the radical addition of heptafluoro-2-iodopropane to ethene. The second chapter deals with the synthesis and reactivity of Au trifluoromethyl complexes. A series of complexes of the type [Au(CF3)L] (L = PPh3, PMe3, 0.5 dppe, P(OEt)3, NHC carbenes, or isonitriles) was prepared by reaction of [Au(Cl)L] with AgF and trifluoromethyltrimethylsilane. Oxidative addition of PhICl2, Br2 I2 o ICl to [Au(CF3)(IPr)] (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-1-ilydene)) led to the corresponding square-planar dihalo complexes. With the exception of the diiodo derivative, these Au(III) complexes are thermically stable, but they undergo photoreductive elimination reactions of halotrifluoromethanes when they are irradiated with UV light. The reactions of [Cu(CF3)(phen)] (phen = 1,10-phenantroline) with Au(III) complexes of the type [AuCl2(C^N)] (C^N = C- and N-donor cyclometalated ligand) led to complexes of the types [AuCl(CF3)(C^N)] and [Au(CF3)2(C^N)]. These species are thermally and photochemically stable against reductive elimination. The third chapter of this thesis reports the synthesis of Au(III) pincer complexes containing the ligand C^Npz^C, wich presents a central pyrazine unit with two 4-t-butilphenyl substituents in the positions 2 and 6. This new ligand was prepared by coupling reactions and was mercuriated in the ortho position of one of the phenyl rings. Transmetalation to a Au(III) salt followed by intramolecular ortho-auration of the other phenyl group afforded the complex [AuCl(C^Npz^C)]. The chloro ligand was substituted by cyano or phenylacetylide ligands. Owing to the presence of the pyrazine unit, some of these complexes present an intense photoluminescence whose color can be tuned by protonation, alkylation or in the presence of metal ions.