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Producción Científica, 19F NMR monitoring shows that heating trans-[AuIIIRf2I2]− solutions (Rf = C6F3Cl2-3,5) leads to formation of cis-[AuRf2I2]−, [AuRf3I]− and [AuRfI3]−via kinetic competition between isomerization and Rf/I scrambling. The system evolution is driven by the easy Rf–I reductive elimination from [AuRfI3]− (forming also [AuI2]−), which is faster than any of the Rf–Rf couplings from the coexisting species, hindering the commonly desired and thermodynamically preferred C–C coupling. A kinetic model where I− dissociation triggers both isomerization and transmetalation steps is proposed, which fits well the experimental data. DFT calculations support that the lower bond strength of AuIII–I compared to other halides produces a pathway switch that makes C–I coupling kinetically preferred. Consequently, it is better avoided in reactions looking for C–C coupling.

Producción Científica, The synthesis of aryl–alkynyl compounds is usually achieved via Sonogashira catalysis, but this is inefficient for fluorinated aryls. An alternative method reported by Shirakawa and Hiyama, using alkynylstannanes and hemilabile PN ligands, works apparently fine for conventional aryls, but it is also poor for fluorinated aryls. The revision of the unusual literature cycle reveals the existence and nature of unreported byproducts and uncovers coexisting cycles and other aspects that explain the reasons for the conflict. This knowledge provides a full understanding of the real complexity of these aryl/alkynylstannane systems and the deviations of their evolution from that of a classic Stille process, providing the clues to design several very efficient alternatives for the catalytic synthesis of the desired ArF–alkynyl compounds in almost quantitative yield. The same protocols are also very efficient for the catalytic synthesis of alkynyl–alkynyl’ hetero- and homocoupling., Ministerio de Asuntos Económicos y Transformación Digital (project PID2020- 118547GB-I00), Junta de Castilla y León (project VA224P20), Irish Research Council (GOIPD/2020/701), Universidad de Valladolid (Margarita Salas program, ref. CONVREC- 2021-221)

Producción Científica, Agostic interactions were observed in the bound mesityl group in a series of iron compounds bearing a bis(NHC) pincer CCC ligand. The L-type ligand on [(CCC)FeIIMes(L)] complexes influences the strength of the agostic interaction and is manifested in the upfield shift of the 1H NMR resonance for the mesityl methyl resonances. The nature of the interaction was further investigated by density functional theory calculations, allowing rationalization of some unexpected trends and proving to be a powerful predictive tool., Universidad de Valladolid. Margarita Salas Postdoctoral Fellowship (CONVREC-2021-221)

Producción Científica, Aryl rearrangements triggered by Cl− extraction from trans-[AuIII(Rf)2Cl2]− (Rf = C6F3Cl2-3,5), led quickly to a mixture of [Au(Rf)3(solv)], cis-[Au(Rf)2Cl(solv)] and [Au(Rf)Cl2(solv)] (solv = OEt2, OH2). 19F NMR and X-ray diffraction studies led us to identify the species present in solution and the role of the solvent in their formation, while DFT calculations confirm the thermodynamic basis of their evolution. Very different Rf–Rf coupling rates are found from (μ-Cl)2[cis-Au(Rf)2]2 or cis-[Au(Rf)2ClL] species (L = OEt2, NCMe, Cl−) depending on the coordination strength of the ligand or solvent in the fourth position., Ministerio de Economía, Industria y Competitividad (Projects CTQ2017-89217-Pand CTQ2016-80913-P)

Producción Científica, Neutral palladium(II) complexes [Pd(Rf)X(P–L)] (Rf = 3,5-C6Cl2F3, X = Cl, I, OTf) with P–P (dppe and dppf) and P–N (PPh2(bzN)) ligands have chelated structures in the solid-state, except for P–L = dppf and X = Cl, were chelated and dimeric bridged structures are found. The species present in solution in different solvents (CDCl3, THF, NMP and HMPA) have been characterised by 19F and 31P{1H} NMR and conductivity studies. Some [Pd(Rf)X(P–L)] complexes are involved in equilibria with [Pd(Rf)(solv)(P–L)]X, depending on the solvent and X. The ΔH° and ΔS° values of these equilibria explain the variations of ionic vs. neutral complexes in the range 183–293 K. Overall the order of coordination strength of solvents and anionic ligands is: HMPA ≫ NMP > THF and I−, Cl− > TfO−. This coordination preference is determining the complexes participating in the alkynyl transmetalation from PhC[triple bond, length as m-dash]CSnBu3 to [Pd(Rf)X(P–L)] (X = OTf, I) in THF and subsequent coupling. Very different reaction rates and stability of intermediates are observed for similar complexes, revealing neglected complexities that catalytic cycles have to deal with. Rich information on the evolution of these Stille systems after transmetalation has been obtained that leads to proposal of a common behaviour for complexes with dppe and PPh2(bzN), but a different evolution for the complexes with dppf: this difference leads the latter to produce PhC[triple bond, length as m-dash]CRf and black Pd, whereas the two former yield PhC[triple bond, length as m-dash]CRf and [Pd(C[triple bond, length as m-dash]CPh)(SnBu3)(dppe)] or [Pd(C[triple bond, length as m-dash]CPh)(SnBu3){PPh2(bzN)}]., Ministerio de Economía, Industria y Competitividad (projects CTQ2016-80913-P and CTQ2017-89217-P), Junta de Castilla y León (project VA062G18, UIC 176)

Producción Científica, Experiments mixing the stable 16e 5-coordinate complexes [RhCp*Ar2] (Cp* = C5Me5; Ar = C6F5, C6F3Cl2-3,5) uncover fast aryl transmetalations. Unexpectedly, as supported computationally, these exchanges are not spontaneous, but catalyzed by minute amounts of 18e (μ-OH)2[RhCp*Ar]2 as a source of 16e [RhCp*Ar(OH)]. The OH group is an amazingly efficient bridging partner to diminish the activation barrier of transmetalation., 2019-04-04, Ministerio de Economía, Industria y Competitividad (Projects CTQ2016-80913-P and CTQ2014-52796-P), Junta de Castilla y León (programa de apoyo a proyectos de investigación – Ref. VA051P17)

Producción Científica, The well known [RhL4]n(anion)n structures, with RhI···RhI d8···d8 interactions, are replaced by others with RhI···AuI d8···d10 interactions such as [{RhL4}{Au(CN)2}] (L = 2,6-Xylylisocyanide) or [{RhL4}{Au(CN)2} {RhL4}{Au2(CN)3}·4(CHCl3)]∞ when the anion is [Au(CN)2]–. Orbital (Rh···Au), coulombic, and inter-unit π-π aryl stacking interactions stabilize these crystal structures., Ministerio de Economía, Industria y Competitividad (grant CTQ2017-89217-P), Junta de Castilla y León (project VA038G18)

Producción Científica, By combining kinetic experiments, theoretical calculations and microkinetic modelling, we show that the Pf/Rf (C6F5/C6Cl2F3) exchange between [AuPf(AsPh3)] and trans-[RhRf(CO)(AsPh3)2] does not occur through the typical concerted Pf/Rf transmetalation via electron deficient double bridges. Instead, it involves asymmetric oxidative insertion of the RhI complex into the (Ph3As)Au–Pf bond producing a [(Ph3As)Au–RhPfRf(CO)(AsPh3)2] intermediate, followed by isomerization and reductive elimination of [AuRf(AsPh3)]. Interesting differences are found between the LAu–Ar asymmetric oxidative insertion and the classical oxidative addition process of H2 to Vaska's complexes., Ministerio de Economía, Industria y Competitividad (grants CTQ2016‐80913‐P / CTQ2017‐89217‐P), Junta de Castilla y León (projects VA051P17 / VA062G18 / UIC176)