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Complexes [(NHC)MCl] (M = coinage metal) have been evaluated as catalyst for the olefin aziridination reaction using PhI=NTs as nitrene source, with moderate to high activity being found depending of the metal and the olefin. At variance with frequently employed copper catalysts with bi-, tri- or tetradentate, N-donor ligands, these monodentante, C-donor ligand infer a remarkable effect in the reaction mechanism. Experimental evidences support the proposal of a concerted mechanism and the absence of radical intermediates, which are the commonly proposed species involved in these nitrene transfer reactions., We thank to Ministerio de Ciencia e Innovación for Grant PID2020-113797RB-C21, also financed by FEDER “Una manera de hacer Europa”. We also thank Junta de Andalucía (P20-00348) and Universidad de Huelva (P.O.Feder UHU-202016).

The direct oxidation of benzene into phenol using molecular oxygen at very mild temperatures can be promoted in the presence of the copper complex TpBr3Cu(NCMe) in the homogeneous phase in the presence of ascorbic acid as the source of protons and electrons. The stoichiometric nature, relative to copper, of this transformation prompted a thorough DFT study in order to understand the reaction pathway. As a result, the dinuclear species TpBr3CuII(μ-O•)(μ-OH)CuIITpBr3 is proposed as the relevant structure which is responsible for activating the arene C−H bond leading to phenol formation., We thank the Spanish Ministerio de Ciencia e Innovación for Grants PID2020-113797RB-C21 (also financed by FEDER “Una manera de hacer Europa”) and PID2020 116861GB-I00. We also thank Junta de Andaluci ́ a (P18-RT-1536), the Universidad de Huelva (P.O.Feder UHU-1260216,) and Cátedra CEPSA for funding. E.B. thanks CEPSA for a Ph. D. fellowship. L.T.-S. thanks the Spanish Ministerio de Uni- versidades (grant FPU18/05895)

A family of gold(I) complexes of composition AuCl(ADAP) (ADAP = alkoxydiaminophosphine) has been synthetized through a one-pot simple protocol in which the ADAP ligand is prepared in situ before reaction with the Au(I) source. Structural data demonstrate that these ADAP ligands exert a trans effect superior to those of phosphine or phosphite ligands. Evaluation of the buried volume (%VBur) indicates a steric hindrance higher than those of several NHC, PR3, and P(OR3) ligands, in the context of AuCl(L) complexes. These complexes promote the catalytic transfer of a carbene group from ethyl diazoacetate to alkenes and alkanes. In the case of styrene, both the Csp2−H bonds and the CC bond are functionalized, the relative ratio depending on the catalyst employed and correlating well with the %VBur value. Data available allow proposing that these compounds display quite similar electronic properties but differ in steric properties, a variable that can be readily controlled upon modifying the alkoxy group at the ADAP ligand by simply replacing the starting alcohol employed in the synthesis., Support for this work was provided by the Ministerio de Economia y Competitividad (CTQ2017-82893-C2-1-R) and Universidad de Huelva (PO FEDER 2014-2020-UHU-1260216).

The mild generation of nitrogen-centred radicals from N–F reagents has become a convenient synthetic tool. This methodology provides access to the aminative difunctionalisation of alkenes and alkynes and the radical ring-opening of cyclopropanes, among other similar transformations. This review article aims to provide an overview of recent developments of such processes involving radical reactions and N–F reagents using copper-based catalysts., We thank Ministerio de Economía y Competitividad (MINECO) (CTQ2017-82893-C2-1-R) and Universidad de Huelva (PO FEDER 2014-2020 UHU-1254043) for grants.

Tris(pyrazolyl)borates (Tpx) have become one of the most broadly used polydentate anionic ligands in coordination chemistry and catalysis since Trofimenko introduced them in 1966. Herein we present a review of the main structural features of Group 11 metal complexes with Tpx ligands, as well as their catalytic properties, can be controlled by ligand steric and electronic factors., We thank MINECO for funding (Grant CTQ2017-82893-C2-1-R).We thank MINECO for Grant CTQ2017-82893-C2-1-R.

The functionalization of the primary sites of alkanes is one of the more challenging areas in catalysis. In this context, a novel effect has been discovered that is responsible for an enhancement in the reactivity of the primary C-H bonds of alkanes in a catalytic system. The copper complex Cu(NCMe) (=hydrotris{[3,5-bis(trifluoromethyl)-4-bromo]-pyrazol-1-yl}borate) catalyzes the functionalization of CnH2n+2 with ethyl diazoacetate upon inserting the CHCO2Et unit into C-H bonds. In addition, the selectivity of the reaction toward the primary sites significantly increased relative to that obtained in neat alkane upon using supercritical carbon dioxide as the reaction medium. This was attributed to the effect of the carbon dioxide molecules that withdraw electron density from the fluorine atoms of the ligand, which enhances the electrophilic nature of the metal center. DFT studies validated this proposal.

Trispyrazolylborate-containing copper and silver complexes are known to promote the catalytic transfer of CHCO2Et groups from ethyl diazoacetate onto carbon–hydrogen bonds of alkanes C2H2n+2. In this account the knowledge compiled for this transformation regarding the design of the catalyst to enhance activity and selectivity is presented, aiming researchers to continue the development of better catalytic systems for this simple reaction employing the readily available alkanes.

Computational chemistry plays a key role in the construction of the current understanding of the reaction mechanisms for the reaction of coinage metal complexes with hydrocarbons. Carbene precursors (diazo compounds) or nitrene precursors (hypervalent iodine compounds or azides) react with the catalyst complexes giving rise to highly reactive metallocarbene or metallonitrene intermediates, which are difficult to observe experimentally. DFT calculations allow the characterization of these intermediates and of their reactivity with hydrocarbons, leading to C–H insertion, aziridination or oxazole synthesis. This review summarizes computational work in the last decade in this research field, which has progressed in collaboration with experimental knowledge on these systems.

A series of Cu(I), Ag(I), and Au(I) complexes incorporating a new family of imidazopyridin-3-ylidene ligands substituted by a diphenylpyrrolidino group at N(1) and aryl groups at C(5) has been synthesized and their structures determined by X-ray diffraction analysis. This structural study has revealed an extremely high steric protection of the metal center by the bulky heterobicyclic carbenes, while the inversion at the exocyclic N(sp3) atom provides a remarkable flexibility.

International audience; The reaction of esters with ethyl diazoacetate catalyzed by the complex [F-27-Tp(4 Bo, 3CF2CF3)Ag(acetone)] generates alpha-(acyloxy)acetates in moderate to high yields. This is a novel transformation in the context of carbene-transfer reactions from diazo compounds that, according to experimental and theoretical data, is suggested to occur through zwitterionic intermediates.

After the first step a cyclopropane intermediate is obtained which is directly converted to indole derivatives (III), (VI), (VII), and (IX) after silica gel column chromatography.

A novel fluorinated ligand, the anionic PhB(CH2P(p-CF 3C6H4)2)3 (PhBP 3 p-CF3Ph), has been synthesized and characterized, as well as its corresponding thallium, copper, and silver derivatives. The presence of fluorine atoms in the ligand structure induced the desired effect of enhancing electrophilic character at the metal center, without promoting substantial changes in the ligand skeleton compared with the parent ligand PhB(CH2PPh2)3 - (PhBP3). Olefin aziridination and C-H amidation reactions have been induced with those complexes as catalyst precursors. The copper derivative catalyzed the olefin aziridination of an array of olefins bearing either electron-donating or electron-withdrawing groups. The silver analogue was found to promote the C-H amidation of a series of substrates in moderate to high yields. © 2014 American Chemical Society.

Novel tris(pyrazolylmethyl)amine ligands TpaMe3, Tpa*,Br, and TpaBr3 have been synthesized and structurally characterized. The coordination chemistries of these three new tetradentate tripodal ligands and the already known Tpa and Tpa* have been explored using different copper(I) salts as starting materials. Cationic copper(I) complexes [TpaxCu]PF6 (1-4) have been isolated from the reaction of [Cu(NCMe)4]PF6 and 1 equiv of the ligand. Complexes 2 (Tpax = Tpa*) and 3 (Tpax = TpaMe3) have been characterized by X-ray studies. The former is a 1D helical coordination polymer, and the latter is a tetranuclear helicate. In both structures, the Tpax ligand adopts a μ2: κ2:κ1-coordination mode. However, in solution, all of the four complexes form fluxional species. When CuI is used as the copper(I) source, neutral compounds 5-8 have been obtained. Complexes 6-8 exhibit a 1:1 metal-to-ligand ratio, whereas 5 presents 2:1 stoichiometry. Its solid-state structure has been determined by X-ray diffraction, revealing its 3D polymeric nature. The polymer is composed by the assembly of [Tpa 2Cu4I4] units, in which Cu4I 4 presents a step-stair structure. The Tpa ligands bridge the Cu 4I4 clusters, adopting also a μ2: κ2:κ1-coordination mode. As observed for the cationic derivatives, the NMR spectra of 5-8 show the equivalence of the three pyrazolyl arms of the ligands in these complexes. The reactivities of cationic copper(I) derivatives 1-4 with PPh3 and CO have been explored. In all cases, 1:1 adducts [TpaxCuL]PF6 [L = PPh3 (9-11), CO (12-15)] have been isolated. The crystal structure of [Tpa*Cu(PPh3)]PF6 (9) has been obtained, showing that the coordination geometry around copper(I) is trigonal-pyramidal with the apical position occupied by the tertiary amine N atom. The Tpa* ligand binds the Cu center to three of its four N atoms, with one pyrazolyl arm remaining uncoordinated. In solution, the carbonyl adducts 13-15 exist as a mixture of two isomers; the four- and five-coordinate species can be distinguished by means of their IR νCO stretching bands. Finally, the catalytic activities of complexes 1-4 have been demonstrated in carbene- and nitrene-transfer reactions. © 2014 American Chemical Society.

The synthesis of novel fluorinated symmetrical and unsymmetrical imidazolium salts as well as their corresponding coinage metal complexes is described. The silver derivatives were prepared using Ag2O as the metal source and the subsequent (NHC)AgX complexes were successfully employed in the preparation of the corresponding Cu(I) and Au(I) complexes through transmetallation reactions. Halide extrusion from (NHC)AuCl complexes in the presence of labile ligands also allowed the isolation of Au(I) cationic complexes [(NHC)Au(L)]X. The molecular structures of relevant examples of the neutral and ionic complexes have been unambiguously determined by X-ray studies., The authors thank Agencia Estatal de Investigación (AEI)/FEDER (CTQ2017-82893-C2-1-R, CTQ2016- 75960-P), Red Intecat CTQ2016-81923-REDC, the AGAUR (2017 SGR 1257), and CERCA Program/Generalitat de Catalunya for financial support. M. D. R. thanks the Ministerio de Educación y Ciencia (MEC) for a FPU fellowship and C. G.-M. thanks Agencia Estatal de Investigación for a FPI predoctoral fellowship.

The sequential reaction of two different furans and PhI=NTs produces 1,2-dihydropyridines in a quantitative manner in the presence of TpBr3Cu(NCMe) (TpBr3 = hydrotris(3,4,5-tribromopyrazolyl)borate) as the catalyst under very mild conditions. The use of a furan and ethyl vinyl ether with PhI=NTs has led to the corresponding 1,2,3,4-tetrahydropyridine.

Three novel Cu(I) complexes bearing tris(pyrazolyl)methane ligands, Tpm(x), have been prepared from reactions of equimolar amounts of CuI and the ligands Tpm, (HC(pz)(3)), Tpm*, (HC(3,5-Me(2)-pz)(3)), and Tpm(Ms), (HC(3-Ms-pz)(3)). X-ray diffraction studies have shown that the Tpm and Tpm(Ms) derivatives exhibit a 2:1 Cu:ligand ratio, whereas the Tpm* complex is a mononuclear species in nature. The latter has been employed as a precatalyst in the arylation of amides and aromatic thiols with good activity. The synthesis of a Tpm*Cu(I)-phthalimidate, a feasible intermediate in this catalytic process, has also been performed. Low temperature (1)H NMR studies in CDCl(3) have indicated that this complex exists in solution as a mixture of two, neutral and ionic forms. Conductivity measurements have reinforced this proposal, the ionic form predominating in a very polar solvent such as DMSO. The reaction of Tpm*Cu(I)-phthalimidate with iodobenzene afforded the expected C-N coupling product in 76% yield accounting for its role as an intermediate in this transformation.

The novel complexes [(PhBP3)Cu(L)] (PhBP3 = PhB(CH2PPh2)3, L = PPh3, 1; L = tetrahydrofuran, 2) have been synthesized and spectroscopically and, in the case of 1, structurally characterized. Both c...

Di- and trinuclear complexes of copper(I) bearing bis- or tris-N-heterocyclic carbene ligands have been prepared and evaluated as catalysts in nitrene transfer reactions from PhI=NTs to unsaturated and saturated substrates (olefin aziridination and C–H bond amidation) and carbene transfer reactions from diazo compounds to olefins. The complexes exhibited moderate-to-high catalytic activity in both processes. The tosylamidation of C–H bonds, previously unreported with a NHC-containing copper catalyst, was promoted by the dinuclear complexes.

DFT computational methods were applied to the mechanistic study of the formation of fumarate and maleate derivatives in a solution containing alkane, TpBr3M [M=Cu, Ag; TpBr3=hydrotris(3,4,5-tribromopyrazolyl)borate] and methyl diazoacetate. These solutions are the experimentally reported conditions for carbene insertion into alkane C-H bonds, a procedure that usually competes with a nondesired reaction, producing fumarate and/or maleate derivatives. Several mechanisms are analyzed. The preferred mechanism proceeds through a direct reaction between a metallocarbene complex intermediate and a diazo molecule. The computational results explain all of the available experimental evidence and provide important information on the behavior of these systems., Financial support from the ICIQ foundation, the Spanish MICINN (CTQ2008-06866-CO2-02/BQU, CTQ2008-00042/BQU), Consolider Ingenio 2010 (CSD2006-0003,) and the Catalan DIUE (2009SGR0259) is acknowledged.

The direct functionalization of aromatic C-H bonds by carbene insertion from diazocompounds catalyzed by gold complexes with N-heterocyclic ligands is described. The reaction is completely selective toward the Csp2-H bonds, other Csp3-H bonds remaining unreacted. A study with a several NHC ligands in Au(I) and Au(III) complexes has been performed. A potential application in profen derivatives has also been developed, DGI (CTQ2008-00042BQU and Consolider Ingenio 2010, Grant CSD2006-0003) and Junta de Andalucía (P07-FQM-02870)

The complexes [Au2M2(C6F5)4(NCMe)2]n (M = Cu, 1; M = Ag, 2) have been tested as catalysts for the functionalization of alkanes by the carbene insertion methodology, using ethyl diazoacetate as the carbene source. Moderate to high conversions have been obtained. The observed selectivities seem to favor the proposal that the active metal for catalysis is the Cu/Ag center, the Au(C6F5)2 unit acting as a spectator ligand in both cases., DGI for funding (CTQ2008-00042/BQU and CTQ2010-20500-C02-02)

14 páginas, 12 figuras, 1 tabla, 13 esquemas., Carbon−halogen (C−X) bonds (X = Cl, Br) can be easily functionalized with ethyl diazoacetate (N2CHCO2Et) in the presence of silver-based catalysts containing the TpxAg core (Tpx = hydrotrispyrazolylborate ligand). Polyhalomethanes are converted into products derived from the formal insertion of the carbene CHCO2Et units into the C−X bond. In the case of monohaloalkanes (C4−C6), cleavage of the C−X bond is observed, with formation of XCH2CO2Et and the corresponding olefin. Experimental evidence and theoretical calculations have led to the proposal of a novel mechanism to account for these transformations, in which the metal participates along the pathway in all the reaction steps. Among the experimental data, the first example of a metal-induced, asymmetric functionalization of a C−Cl bond by carbene insertion is included (ee = 14 ± 2%)., Financial support from MICINN (Grants CTQ2008-06866-CO2-02/BQU, CTQ2008-00042/BQU, Consolider Ingenio 2010 CSD2006-0003), the Catalan DURSI (project 2005SGR00715), the Junta de Andalucía (Grant P07-FQM 2870), and the ICIQ foundation is acknowledged. J.U. also thanks the Junta de Andalucía for a student fellowship. A.A.C.B. thanks the Spanish MICINN for a “Juan de la Cierva” contract.

A series of complexes of general formulae Tp x Cu have been employed as the catalyst for the styrene cyclopropanation reaction with ethyl diazoacetate, both under homogeneous and heterogeneous conditions. Several solid supports have been tested, with silica gel being the most convenient for this transformation. A comparison of the results obtained under both conditions has shown that the catalytic pocket is affected by the support.

Copper complexes containing chiral N-heterocyclic carbene ligands catalyze the regioselective nucleophilic boryl attack at the β-carbon of α,β-unsaturated esters with enantioselectivities up to 74% ee, depending on the nature of the ester group.

The carbon−hydrogen bonds of alkanes, R−H, can be converted in high yields into amino functionalities (R−NHTs; Ts = p-toluensulfonyl), with the aid of silver-based catalysts in a reaction implying the thermal (80 °C) insertion of a nitrene NTs unit into the C−H bond of the hydrocarbon. Complexes TpxAg (Tpx = hydrotris(pyrazolyl)borate ligand) serve as catalysts and PhI═NTs serves as the nitrene source.

The functionalization of unreactive C−H bonds of several hydrocarbons has been achieved at room temperature by the formal insertion of carbene/CHCO2Et units (from ethyl diazoacetate) into such bonds, using copper-based catalysts in a biphasic reaction medium (ionic liquid-hydrocarbon). Catalyst and product separation has been carried out easily, and the recycle of the catalyst for five cycles has been achieved without any loss of catalytic activity.

Thermal reactions between [RuCl2(diene)]n (diene = 2,5-norbornadiene, nbd; 1,5-cyclooctadiene, cod) with an excess of N,N,N',N'-tetramethylethylene diamine (tmeda) afforded derivatives [RuCl2(diene)(tmeda)] (diene = nbd, 1; cod, 2) as a mixture of cis and trans isomers. When thermolysis was performed under H2 mixtures of hydride species [RuCl(H)(diene)(tmeda)] (diene = nbd, 3; cod, 4) and the bis-tmeda adduct trans-[RuCl2(tmeda)2] (5) were obtained in different ratios depending upon the reaction conditions and reaction times. Heating polymeric Ru(II) precursors in toluene in the presence of a 5-fold excess of the bulkier N,N,N',N'-tetraethylethylene diamine (teeda) resulted in a rare diamine dealkylation process with formation of trans-[RuCl2(nbd)(Et2NCH2CH2NHEt)] (6) and trans-[RuCl2(cod)(EtHNCH2CH2NHEt)] (7) in high yields. The presence of N-H functionalities in the coordinated diamine ligands of 6 and 7 was unambiguously established by single-crystal X-ray diffraction studies. The dealkylation process of the teeda ligand seems to proceed intramolecularly as shown by solution NMR studies performed with the soluble Ru(II) precursors trans-[RuCl2(amine)2(diene)] (diene = nbd, amine = morpholine, 9; diene = cod, amine = Et2NH, 10). The above complexes [RuCl2(diene)(diamine)] have been tested as precatalysts in the hydrogenation of ketones both for transfer as well as direct hydrogenation, the latter route being the most effective.

Cu(I) complexes containing trispyrazolylborate ligands efficiently catalyze the atom transfer radical addition (ATRA) of polyhalogenated alkanes to various olefins under mild conditions. The catalytic activity is enhanced when bulky and electron donating Tpx ligands are employed. Kinetic data have allowed the proposal of a mechanistic interpretation that includes a Cu(II) pentacoordinated species that regulates the catalytic cycle.

The reactions of organic azides and alkynes catalysed by copper species represent the prototypical examples of click chemistry. The so-called CuAAC reaction (copper-catalysed azide-alkyne cycloaddition), discovered in 2002, has been expanded since then to become an excellent tool in organic synthesis. In this contribution the recent results described in the literature since 2010 are reviewed, classified according to the nature of the catalyst precursor: copper(I) or copper(II) salts or complexes, metallic or nano-particulated copper and several solid-supported copper systems.

DFT Becke3LYP calculations are applied to the computational study of the activation of alkane C−H bonds by metallocarbene homoscorpionate complexes. A total of 16 different combinations of metallocarbene complex and alkane are explored, defined by the use of TpAgC(H)(CO2CH3), TpBr3AgC(H)(CO2CH3), TpCuC(H)(CO2CH3), and TpBr3CuC(H)(CO2CH3) species as metallocarbene and methane, ethane, propane, and butane as alkane. The reaction is found to be under kinetic control, and the selectivity is decided in a step with a low-barrier transition state where the key bond-breaking and bond-forming processes take place in a concerted way. This transition state has several possible conformations, which are systematically explored to find the one with lowest energy for each reaction. Variations of the energy barrier as a function of the nature of metal, ligand, and alkane are analyzed and discussed.

Facile alkane functionalization by means of the insertion of :CHCO2Et, from ethyl diazoacetate, into carbon−hydrogen bonds mediated by catalytic amounts of (NHC)MCl (NHC = N-heterocyclic ligand; M = Cu, Au) and a halide scavenger MX has been achieved. This chemistry includes the insertion of the carbene fragment into alkane primary positions with Cu- and Au-based catalysts. The nature of the counterion X and of the NHC ligand have a significant effect on the overall yields and regioselectivity of the reaction.

The complexes [TpBr3Ag]2·CH3COCH3 (1) and TpBr3Ag(thf) (2) catalyze the insertion of the :CHCO2Et group from ethyl diazoacetate (EDA) into the saturated C−H bonds of several C5, C6, and C8 linear and branched alkanes. In addition to secondary and/or tertiary sites, the unprecedented insertion into the primary C−H bonds of the substrates studied has been observed with variable regioselectivity, toward the methyl groups, within the range of 40−60% for branched and nearly 25% for linear alkanes.

The new complex Tp B r 3 Ir(C 2 H 4 ) 2 , 1, photochemically activates the C-H bonds of n-pentane in a two-step process, the first one being the formation of an isolable alkyl-hydride intermediate of composition Tp B r 3 Ir(H)(C 2 H 4 )(C 5 H 1 1 ), 3a, that subsequently undergoes β-hydride elimination to generate a terminal olefin complex, Tp B r 3 Ir(H) 2 (C 5 H 1 0 ), 4a. The reaction can also be extended to diethyl ether. In this case, the reaction proceeds by the activation of one of the β-C-H bonds (with respect to the O-ether atom) with formation of the alkyl-hydride 3b and the dehydrogenation product 4b. These processes also compete with the intramolecular C-H activation of one of the coordinated ethylene ligand by the Ir(I) center in 1, which affords the hydride-vinyl complex TpBr3Ir(H)(CH=CH 2 )(C 2 H 4 ), 2. Attempts to thermally induce the above transformations has led to the exclusive formation of a mixture of the hydride-α,ω-butenyl complex Tp B r 3 Ir(H)(CH 2 CH 2 CH=CH 2 ), 5, and the hydride-crotyl complex Tp B r 3 Ir(H)(C 4 H 7 ), 6.

Complexes of general formula TpxCu (Tpx = homoscorpionate ligand) have been employed as catalysts for the insertion of ethyl diazoacetate into C−H bonds of a variety of hydrocarbons and ethers, in moderate to high yields: tertiary, secondary, and primary C−H bonds have been functionalized by this methodology. Particularly interesting is the homologation of O-methyl groups in ethers, which has been achieved for a group of substrates. The existence of electron-withdrawing groups in the Tpx ligand seems to be crucial for the activity and the selectivity of the catalyst.

The complexes TpXCu (TpX = homoscorpionate ligands) efficiently catalyze the insertion of the carbene fragment :CHCO2Et, generated from ethyl diazoacetate, into the OH bond of saturated and unsatur...

The kinetics of the electron transfer reactions between pentaammine(pyrazine)ruthenium(II), [Ru(NH3)5pz]2+ and tris(oxalate)cobalt(III), [Co(C2O4)3]3− and pentaammine(pyridine)ruthenium(II), [Ru(NH3)5py]2+ and tetraammine(pyrazinecarboxylate)cobalt(III), [Co(NH3)4pzCO2]2+ have been studied in aqueous solutions of DNA over the concentration ranges 0 to 2.46 × 10−3 mol dm−3 and 1.23 × 10−4 to 1.00 × 10−3 mol dm−3, respectively. The results are interpreted on the basis of a modified pseudophase model which takes into account the anticooperative character of the binding of the cationic reactants to DNA.

The preparation of (DIPPP)Pd(PR3) and [(DIPPP)(PR3)PdH][OR‘] (DIPPP = bis(1,3-diisopropylphosphino)propane; R = Cy, Et; R‘ = Ar, CF3SO2) is reported. (DIPPP)Pd(PCy3) and [(DIPPP)(PCy3)PdH][CF3SO3] have been structurally characterized. (DIPPP)Pd(PR3) complexes catalyze the reaction of ethylene with carbon monoxide and phenols to give aryl propionates. In situ 31P NMR experiments have shown that the resting state of the catalyst in these transformations is the binuclear species [{(DIPPP)Pd}2(μ-H)(μ-CO)][OPh].

The fixation of the preformed polypyrazolylborate copper(I) complexes BpCu (1), Tp*Cu (2), and [B(pz)4]Cu (3) (Bp = dihydrobispyrazolylborate, H2B(pz)2; Tp* = hydrotris(3,5-dimethyl)pyrazolylborate, HB(pz*)3; B(pz)4 = tetrakispyrazolylborate) on silica gel and their use, under heterogeneous conditions, as catalysts for the olefin cyclopropanation reaction are reported. The catalytic activity is very similar to that observed under homogeneous conditions, as a consequence, according to the studies presented herein, of a ligand-to-support interaction that would involve the hydroxyl groups of the silica surface and the borohydride B−H group and/or the pyrazolyl nitrogen atoms. The strength of such interactions allows the recovery and recycling of the supported catalysts for a number of cycles.

N-donor Lewis bases such as acetonitrile or pyridine react with the Rh(I) compound TpMe2Rh(C2H4)2 (1) to give the Rh(III) derivatives TpMe2Rh(CHCH2)(C2H5)(L) (2, 3) as the kinetic products of the reactions. Upon heating at 60 °C, the acetonitrile adduct 2 converts into TpMe2Rh(C2H4)(NCMe) (5). Under similar conditions, 2 is able to induce the activation of one of the C−H bonds of C6H6, in a process that involves the intermediacy of 1, as demonstrated by isotopic labeling studies. The phosphine adducts TpMe2Rh(C2H4)(PR3) (R = Me, Et) are also efficient reagents for the C−H bond activation of C6H6, py, or thiophene. In the latter case, rupture of the C−S bond is also detected, although the C−S bond activation complexes are thermodynamically disfavored with respect to those derived from the cleavage of one of the α-C−H bonds.

Kinetic studies of the ethyl diazoacetate (EDA) decomposition reaction in the presence of BpCu (1) and in the presence or absence of olefin have led to the determination of several kinetic and thermodynamic parameters, and a consistent mechanism has been proposed for the olefin cyclopropanation reaction. Related studies with the complexes [Cu(bipy)2]I (bipy = bipyridine) and [Cu(bis(oxazoline))2]OTf have shown strong similarities with the results obtained with 1. A general mechanism covering the copper-based systems reported in the literature has been proposed, the real catalyst (i.e., the species to be reacted with EDA) in all cases being a neutral, 14-electron fragment of composition (L−L)Cu (L−L = Bp- and Tp-like ligands, semicorrins, salicylaldehyde derivatives) or, alternatively, the isoelectronic, cationic [(L−L)Cu]+ (for L−L = bis(oxazoline), bipyridine).

The complexes BpCu (1), BpCuL (L = bipy, 2; L = Ph2PCH2CH2PPh2, 3; L = PCy3, 4) and BpCuL2 (L = py, 5; L = PPh3, 6) catalyze the cyclopropanation of olefins in moderate to high yields in the homoge...

The formation and some substitution chemistry of the bis(ethylene) complexes Bp′Rh(C2H4)2 (Bp′ - Bp*; 1*; Bp′ - Bp, 1) are described. Reaction of 1* with 1 equiv. of N-donor ligands or monodentate phosphines (L) leads to the isolation of compounds of general formula Bp*Rh(C2H4)(L). Addition of an excess of amine produces the eighteen electron complexes Bp*Rh(C2H4)(L)2 whereas in the case of the PR3 ligands the second equivalent of the donor gives the disubstituted sixteen electron compounds Bp*Rh(L)2. The ethylene groups in 1* and 1 can also be replaced by carbon monoxide and tert-butyl isocyanide, affording the complexes Bp′Rh(L)2 (L - CO, CN1Bu). The solid state structures of the compounds Bp*Rh(C2H4)2 (1*) and BpRh(PPh3)2 (9) have been determined by X-ray diffraction studies. Crystals of 1* are monoclinic, space group P21/c, with a = 15.129(3), b = 17.501(3), c = 13.425(8) A, β = 111.02(4)°, V = 3318(2) A3, and Dcalc = 1.06 g cm 3 for Z = 8; R = 4.3 and Rw = 4.4. Crystals of 9 are triclinic, space group P21/c, with a = 10.281(2), b = 11.637(2), c = 17.836(8) A, α = 90.09(2), β = 95.77(2), γ = 108.410(13)°, V = 2013(2) A3, and Dcalc = 1.4 g cm 3 for Z = 2; R = 0.0302 and wR = 0.0787.

The complexes TpBr3Cu(NCMe) (1) and TpMsCu (2) catalyze the addition of the :CHCO2Et unit (generated from N2CHCO2Et, EDA) to benzene to give a cycloheptatriene ring, in analogy with the Buchner reaction. When alkyl groups are attached to the aromatic rings, the selectivity of the reaction can be oriented toward addition or, alternatively, to the insertion into an alkyl C−H bond by using 1 or 2, respectively.

Intramolecular 1,3-dipolar cycloaddition of alkoxycarbonyl-substituted azomethine ylides to ester carbonyl was realized for the first time in the reaction of imines of O-acylsalicylic aldehyde with ethyl diazoacetate in the presence of Cu(tfacac)(2). The stereoselectivity of the cycloaddition is explained using DFT calculations.

Reaction of Tp{prime}(CO){sub 3}WH(Tp{prime}=hydridotris(3.5-dimethyl-1-pyrazolyl)borate) with tosyl azide in THF at reflux affords the amido complex Tp{prime}(CO){sub 2}W(N(H)Ts) (1). Crystals of 1 are monoclinic, space group P2{sub 1}/n, with cell parameters a = 12.4855(11) A, b=20.5976(16){Angstrom}, c= 12.7311(11){Angstrom}, {beta}=96.510(10){degrees}, V=3253.0(5) {Angstrom}{sup 3}, and D{sub calcd}=1.591 g cm{sup {minus}3} for Z = 4. Least-squares refinement led to final R and R{sub w} values of 0.038 and 0.046, respectively. Complex 1 undergoes oxidation by silver triflate or iodine to give the imido complexes [Tp{prime}-(CO){sub 2}W(NTs)]X (X=OTf, 2a; X=I{sub 3},2b). The single crystal X-ray structure of 2b is also reported (orthorhombic, space group Pcab, a= 15.1764(16) {Angstrom}, b = 16.8890(14) {Angstrom}, c=26l909(3) {Angstrom}, V=6897.2(13) {Angstrom}{sup 3}, and D{sub calcd}= 2.094 g cm{sup {minus}3} for Z=8; R=0.044, R{sub 2}=0.052). The cationic nitrene complex 2 reacts with LiBH{sub 4} to regenerate the amido compound 1. Addition of trimethylphosphine to solutions of 2 leads to the formation of three species the phosphinimine TsN=PMe3 (3) and two tungsten complexes, [Tp{prime}(CO){sub 2}W(PMe{sub 3}){sub 2}][X](X = OTf, 4a; X=I{sub 3}, 4b) and [Tp{prime}(CO)(PMe{sub 3})W(NTs)][X] (X=OTf, 5a; X=I{sub 3}, 5b). Complex 5b undergoes substitution by iodide to produce the tungsten monocarbonyl Tp{prime}(CO)IW(NTs) (6).

Experimental as well as theoretical studies have been carried out with the aim of elucidating the mechanism of the atom transfer radical addition (ATRA) of styrene and carbon tetrachloride with a TpxCu(NCMe) complex as the catalyst precursor (Tpx = hydrotrispyrazolyl−borate ligand). The studies shown herein demonstrate the effect of different variables in the kinetic behavior. A mechanistic proposal consistent with theoretical and experimental data is presented., We thank the MICINN (Grants CTQ2008-00042BQU, CTQ2008-06866-CO2-02/BQU, and Consolider Ingenio 2010 CSD2006-0003) and the Junta de Andalucía (Proyecto P07-FQM-02794) for financial support.