RESUMEN
The reactions leading to the formation of C-heteroatom bonds in the coordination sphere of Au(III) complexes are uncommon, and their mechanisms are not well known. This work reports on the synthesis and reductive elimination reactions of a series of Au(III) methyl complexes containing different Au-heteroatom bonds. Complexes [Au(CF3)(Me)(X)(PR3)] (R = Ph, X = OTf, OClO3, ONO2, OC(O)CF3, F, Cl, Br; R = Cy, X = Me, OTf, Br) were obtained by the reaction of trans-[Au(CF3)(Me)2(PR3)] (R = Ph, Cy) with HX. The cationic complex cis-[Au(CF3)(Me)(PPh3)2]OTf was obtained by the reaction of [Au(CF3)(Me)(OTf)(PPh3)] with PPh3. Heating these complexes led to the reductive elimination of MeX (X = Me, Ph3P+, OTf, OClO3, ONO2, OC(O)CF3, F, Cl, Br). Mechanistic studies indicate that these reductive elimination reactions occur either through (a) the formation of tricoordinate intermediates by phosphine dissociation, followed by reductive elimination of MeX, or (b) the attack of weakly coordinating anionic (TfO- or ClO4-) or neutral nucleophiles (PPh3 or NEt3) to the Au-bound methyl carbon. The obtained results show for the first time that the nucleophilic substitution should be considered as a likely reductive elimination pathway in Au(III) alkyl complexes.
RESUMEN
New dinuclear Au(I), Au(II) and Au(III) complexes containing (CF2 )n bridging chains were obtained. Metallomacrocycles [Au2 {µ-(CF2 )4 }{µ-diphosphine}] show an uncommon figure-eight structure, the helicity inversion barrier of which is influenced by aurophilic interactions and steric constraints imposed by the diphosphine. Halogenation of LAu(CF2 )4 AuL (L=PPh3 , PMe3 , (dppf)1/2 , (binap)1/2 ) gave [Au(II)]2 species, some of which display unprecedented folded structures with Au-Au bonds. Aurophilic interactions facilitate this oxidation process by preorganizing the starting [Au(I)]2 complexes and lowering its redox potential. The obtained [Au(II)]2 complexes undergo thermal or photochemical elimination of R3 PAuX to give Au(III) perfluorinated auracycles. Evidence of a radical mechanism for these decomposition reactions was obtained.
RESUMEN
The first binuclear AuI compounds containing bridging (CF2 )n chains (n=4, 6, 8) and AuIII metallaperfluorocyclopentanes have been obtained by photoinitiated reactions of LAuMe (L=PPh3 , PMe3 , PCy3 , or IPr) with α,ω-diiodoperfluorocarbons. Complexes LAu(CF2 )4 AuL present an unusual looped structure stabilized by an aurophilic interaction for L=PMe3 , PPh3 , and PCy3 . The study of their dynamic behaviour has provided new insights about the strength of aurophilic interactions in solution, allowing quantification of the energy of a single Auâ â â Au interaction.
RESUMEN
The study of perfluoroalkyl metal complexes is key to understand and improve metal-promoted perfluoroalkylation reactions. Herein, we report the synthesis of the first gold complexes with primary or secondary perfluoroalkyl ligands by photoinitiated reactions between AuI organometallic complexes and iodoperfluoroalkanes. Complexes of the types LAuRF (L=PPh3 or N,N-bis(2,6-diisopropylphenyl)imidazol-2-ylidene; RF =n-C4 F9 , n-C6 F13 , i-C3 F7 , c-C6 F11 ) and [Au(RF )(Ar)I(PPh3 )] (Ar=2,4,6-trimethylphenyl) have been isolated and characterized. Alkynes RF C≡CR were formed by reaction of Ph3 PAuC≡CR (R=Ph, nHex) with IRF (RF =n-C4 F9 , i-C3 F7 ). According to the evidences obtained, this transformation undergoes through a photoinitiated radical mechanism. AuIII complexes [Au(n-C4 F9 )(X)(Y)L] (X=Y=Cl, Br, I, Me; X=Me, Y=I) have been prepared or in situ generated, and their thermal or photochemical decomposition reactions have been studied.
