Comparing Protonolysis and Transmetalation Reactions: Microcalorimetric Studies of C–AuI Bonds in [AuRL] Complexes

Producción CientíficaThe protonolysis of C–Au bonds in [AuRL] organometallic complexes has been studied by calorimetry for twelve R groups. The experimental data have been combined with DFT calculations to obtain Bond Dissociation Energy values (BDE). The C–Au BDE values show a good correlation with the corresponding isolobal C–H BDE values. The heat released in the protonolysis of [AuRL] has also been measured for R = Ph and L = P(OPh)3, PPh3, PMe3, PCy3, and IPr, and these values strongly depend on the trans influence of L because of the mutual destabilization of the L–Au and Au–C bonds. The enthalpy of the transmetalation reactions [AuR(PPh3)] + SnIBu3 → [AuI(PPh3)] + SnRBu3 for seven R groups have been measured and compared with the corresponding [AuR(PPh3)] protonolysis.Ministerio de Economía, Industria y Competitividad (Project CTQ2016-80913-P)Junta de Castilla y León (Project VA 051P17

d8···d10 RhI···AuI Interactions in Rh 2,6-Xylylisocyanide Complexes with [Au(CN)2]: Bond Analysis and Crystal Effects

Producción CientíficaThe 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

Olefin Insertion Versus Cross-Coupling in trans-[Pd(Ar)X(AsPh3)2] Complexes (X = I, F, CF3) Treated with a Phosphine-EWOlefin Ligand to Induce Ar–X Coupling

Producción CientíficaAddition of the coupling promoter PEWO ligand 1-(Ph2P),2-(CH═CH–C(O)Ph)C6F4 (PhPEWO-F) to precursors with the displaceable AsPh3 ligand trans-[PdXAr(AsPh3)2] (X = I, F, CF3) fails to induce the pursued Ar–F or Ar–CF3 coupling and results in formation of products of olefin insertion into the Pd–Ar bond for X = I, CF3, and in Ar–Ar coupling for X = F. In the course of the processes, trans-[PdXAr(PhPEWO-F)(AsPh3)] intermediates are observed for X = I, F, CF3, with P-coordinated PhPEWO-F monodentate ligands and a dangling olefin group. For X = I, CF3, subsequent insertion of the double bond into the Pd–Ar bond and O-coordination gives rise to complexes with a P,C,O-pincer system. The observed insertion rates suggest that the limiting step toward insertion is the trans to cis isomerization, while insertion itself is very fast. This is supported by the fast insertion observed when PhPEWO-F is added to cis-[Pd(CF3)Ar(3-F-py)2]. The insertion mechanism in PhPEWO-F resembles the initial phase of the dearomative rearrangement mechanism reported for PdArBrL (L = dialkyl biaryl phosphine).Ministerio de Economía, Industria y Competitividad (Projects CTQ2014-52796-P, CTQ2016-80913-P, and CTQ2014-52974-REDC)Junta de Castilla y León (programa de apoyo a proyectos de investigación – Ref. VA256U13

In Situ Generation of ArCu from CuF2 Makes Coupling of Bulky Aryl Silanes Feasible and Highly Efficient

Producción CientíficaA bimetallic system Pd/CuF2, catalytic in Pd and stoichiometric in Cu, is very efficient and selective for the coupling of fairly hindered aryl silanes with aryl, anisyl, phenylaldehide, or pyridyl iodides of conventional size. The reaction involves the activation of the silane by CuII followed by disproportionation and transmetalation from the CuI(aryl) to PdII, on which coupling takes place. The CuIII formed in the disproportionation is reduced to CuI(aryl) by the aryl silane in excess, so that the CuF2 used is fully converted into CuI(aryl) and used in the coupling. Moreover, no extra source of fluoride is needed. Interesting size selectivity towards coupling is found in competitive reactions of hindered aryl silanes. Easily accessible [PdCl2(IDM)(AsPh3)] is by far the best catalyst, and the isolated products are esentially free of As or Pd (< 1 ppm). The mechanistic aspects of the process are experimentally examined and discussed.Ministerio de Economía, Industria y Competitividad (CTQ2013-48406-P)Junta de Castilla y León (programa de apoyo a proyectos de investigación – Ref. VA256U13

Dramatic Mechanistic Switch in Sn/AuI Group Exchanges: Transmetalation vs. Oxidative Addition

Producción CientíficaThe mechanism of Ph/X exchange in reactions involving SnPhnBu3 and [AuXL] complexes switches dramatically from the usual concerted mechanism involving Ar/X mixed bridges when X = Cl, to an unexpected oxidative addition/reductive elimination pathway via an AuIII intermediate when X = vinyl

Supramolecular aggregates of metallo–organic acids with stilbazoles. Formation of columnar mesophases and Langmuir films

Producción CientíficaSupramolecular metal complexes formed through hydrogen bonding between tris(3,4,5-decyloxy)stilbazole and several metallo–organic acids of the type [Au(R)(CNC6H4CO2H)] (R = C6F5, C6F4OC10H21), [cis-[MCl2(CNC6H4COOH)2] and [trans-[MI2(CNC6H4COOH)2] (M = Pd, Pt) have been synthesized. All the supramolecular palladium and platinum polycatenar aggregates display a hexagonal columnar mesophase at temperatures close to room temperature. Most of the supramolecular trisalkoxystilbazole complexes exhibit luminescent behaviour. Aggregates of [Au(C6F4OC10H21)(CNC6H4CO2H)] and [trans-[MI2(CNC6H4COOH)2] (M = Pd, Pt) form stable Langmuir films at the air–water interface.Ministerio de Ciencia e Innovación (Projects CTQ2011-2513)Junta de Castilla y León (programa de apoyo a proyectos de investigación - Ref. VA248A11-2

The Amide Group as Modulator of Crystalline and Liquid Crystalline Structures in Isocyano-alkylanilide Silver (I) Complexes

Producción CientíficaSilver(I) complexes [AgX(CNR] and [Ag(CNR)2]X (X = anionic ligand), containing an amide-functionalized isocyanide, CNR = CN-C6H4-NHCOR, have been synthesized and their X-ray structures have been determined for [Ag(X)(CN-C6H4-NHCOCH3)] (X = NO3ˉ, CF3SO3ˉ) and [Ag(CN-C6H4-NHCOCH3)2]X (X = NO3ˉ, CF3SO3ˉ, BF4ˉ). All the crystal structures show a packing of polymeric chains formed through Ag–O=Camide interactions. These chains associate in layers through hydrogen bonds involving the amide group, and by further interactions of the metal ion with oxygen-donor moieties. Substitution of the Me group in the amide by a nonyl chain (R = C9H19) leads to neutral [Ag(NO3)(CN-C6H4-NHCOC9H19)] and ionic [Ag(CN-C6H4-NHCOC9H19)2]X (X = NO3ˉ, CF3SO3ˉ, H25C12OSO3ˉ, BF4ˉ) mesomorphic complexes. All of them display smectic liquid crystalline phases compatible with the crystal structures found for the methyl derivatives, and FTIR/ATR spectroscopy confirms that the intermolecular interactions observed in the solid state are preserved in the mesophase.Ministerio de Economía, Industria y Competitividad (CTQ2011-25137)Junta de Castilla y León (programa de apoyo a proyectos de investigación – Ref. VA302U13

Reactivity of Fluorinated-Chalcone Phosphines, RPEWO-F4, Induced by C–F Activation upon Coordination to PdCl2

Producción CientíficaThe E phosphine ligands (R = Ph, o-Tol, Cy), abbreviated as RPEWO-F4, are stable in solution, but they develop a rich reactivity on coordination to PdCl2. The chelate P-olefin coordination to PdCl2 leads eventually to a Z conformation of the fluorinated-chalcone group o-C6F4CH═CHC(O)Ph. From there, a cyclization reaction occurs involving the C═O group and activation of a F atom, yielding a strongly chelated PdCl2(P-carbene) complex. The carbene carbon atom in the complex displays some electrophilicity, which is expressed in hydrolysis, ammonolysis, and oxidation (with peroxide) reactions, affording PdCl2 complexes with new P,C,O-pincer, P,C,N-pincer, or P,O-chelate fluorinated ligands. The C–F activation reactions are slow in comparison to the catalysis rates when the [PdCl2(RPEWO-F4)] complexes have been used in Negishi catalyses. Consequently, the reactivity discussed here is not expected to interfere with the interpretation of the data obtained in Pd-catalytic studies or processes, at least for fast transmetalating nucleophiles.Ministerio de Economía, Industria y Competitividad (projects CTQ2017-89217-P and CTQ2016-80913-P)Junta de Castilla y León (projects VA051P17 and VA062G18

4-Pyridylisocyanide Gold(I) and Gold(I)-plus-Silver(I) Luminescent and Mechanochromic Materials: The Silver Role

Producción CientíficaCrystallographic and DFT examination of the metalloligands [AuAr(CNPy-4)] (Ar = C6F5 (1), C6F3Cl2-3,5 (2)) and their silver complexes [Ag[AuAr(CNPy-4)]2](BF4) (3 and 4) support that the marked luminescence red-shifts observed on moving from 1 to 2, from 1,2 to 3,4, or upon grinding, are not caused by electronic differences (either by changing the aryls C6F5/C6F3Cl2, or by N coordination to silver), nor by non-existent Au···Ag interactions. They are always due to structural changes disturbing stronger π-π stackings in order to allow for shorter Au···Au interactions.Ministerio de Economía, Industria y Competitividad (grant CTQ2017-89217-P )Junta de Castilla y León (project VA038G18

Room‐Temperature Columnar Mesophases in Triazine–Gold Thiolate Metal–Organic Supramolecular Aggregates

Producción CientíficaSupramolecular mono‐ and dinuclear liquid‐crystalline gold(I) aggregates have been synthesized by means of hydrogen bond interactions of 2,4,6‐triarylamino‐1,3,5‐triazine with thiolate moities of gold metalloacids [Au(PR3)(SC6H4COOH)] or [μ‐(binap){Au(SC6H4COOH)}2], in 1:1 and 2:1 molar ratio, respectively. All of the supramolecular aggregates display a stable columnar hexagonal mesophase (Colh) at room‐temperature. The supramolecular arrangement within the columns consists of the one‐dimensional stacking of triazine units, with the core of the attached metallic thioacid fragments acting as the fourth branch. The phosphine‐containing moieties of the metallic thioacid protrude out in the aliphatic continuum. These complexes do not show metallophilic interactions, but this strategy appears very promising for the future design of room‐temperature LC mesophases containing interacting metallic fragments.Ministerio de Ciencia e Innovación (Proyect CTQ2011–25137)Junta de Castilla y León (programa de apoyo a proyectos de investigación – Ref. VA248 A11‐2