Mechanistic and Computational Studies of the Atom Transfer Radical Addition of CCl4 to Styrene Catalyzed by Copper Homoscorpionate Complexes

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 presentedMICINN (Grants CTQ2008–00042BQU, CTQ2008-06866-CO2-02/BQU and Consolider Ingenio 2010 CSD2006-0003) and the Junta de Andalucía (Proyecto P07-FQM-02794)We thank the MICINN (Grants CTQ2008-00042BQU, CTQ2008-06866-CO2-02/BQU, and Consolider Ingenio 2010 CSD2006-0003) and the Junta de Andalucia (Proyecto P07-FQM-02794) for financial support

Group 11 tris(pyrazolyl)methane complexes: structural features and catalytic applications

Tris(pyrazolyl)methane ligands (Tpmx) have been for years a step behind their highly popular boron-anionic analogues, the tris(pyrazolyl)borate ligands (Tpx). However, in the last decade the development of new members of this family of ligands has boosted a number of contributions albeit their use in coordination chemistry. This fact has also triggered the application of metal-Tpmx complexes as catalysts for a range of organic transformations, particularly with group 11 metals. The main structural features of complexes containing the TpmxM (M = Cu, Ag, Au) unit and their success as catalysts in a variety of reactions under homogeneous or heterogeneous conditions are presented.We thank MINECO for support with Grant CTQ2017-82893-C2-1-

Stable N-heterocyclic carbene (NHC)-palladium(0) complexes as active catalysts for olefin cyclopropanation reactions with ethyl diazoacetate

The Pd0 complexes [(NHC)PdLn] (NHC=N-heterocyclic carbene ligand; L=styrene for n=2 or PR3 for n=1) efficiently catalyse olefin cyclopropanation by using ethyl diazoacetate (EDA) as the carbene source with activities that improve on previously described catalytic systems based on this metal. Mechanistic studies have shown that all of these catalyst precursors deliver the same catalytic species in solution, that is, [(IPr)Pd(sty)], a 14e- unsaturated intermediate that further reacts with EDA to afford [(IPr)Pd(=CHCO2Et)(sty)], from which the cyclopropane is formed. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.We thank Prof. P. J. Pérez (Univ. Huelva) for helpful and constructive comments on these studies. We thank the Ministerio de Ciencia e Innovación (grants CTQ2008–00042BQU and CTQ2011–24502) and the Junta de Andalucía (Proyecto P07-FQM-02794) for financial support. CM thanks the MEC for a research fellowshipPeer Reviewe

An effective dual copper-and sulfide-catalytic system for the epoxidation of aldehydes with phenyldiazomethane

Epoxides have been obtained from alde-hydes and phenyldiazomethane using catalytic amounts of both the copper homoscorpionate com-plexes Tp xCuL (Tpx = homoscorpionate ligand; L = acetonitrile or tetrahydrofuran, THF) and dimethyl sulfide (SMe2) in high yields and diasteroselectivities, and with activities higher (TOF = 46 h-1) than those already known with rhodium-or copper-based cata-lysts. Among the copper(I) homoscorpionate com-plexes tested, TpBr3Cu(NCCH 3) showed the highest catalytic activity under mild conditions. The catalytic activity is controlled by electronic effects induced by the Tp x ligand as well as by the stability of the TpxCu(SR 2) adducts. Indeed, in the case of TpMs as ligand, the TpMsCu(THT) (THT = tetrahydrothio-phene) and Tp MsCu(SMe2) species could be isolated as very stable crystalline solids, the molecular struc-ture of the former being confirmed by single-crystal X-ray diffraction analysis. The in situ generation of PhCHN 2 from benzaldehyde tosylhydrazone sodium salt at 60 °C in methyl tert-butyl ether as solvent and TpMsCu(THF) as the catalyst also showed high cata-lytic activities, improving those already reported with copper-based catalysts. © 2013 Wiley-VCH Verlag GmbH&Co. KGaA, Weinheim.Peer Reviewe

The elusive palladium-diazo adduct captured: synthesis, isolation and structural characterization of [(ArNHC-PPh2)Pd(η2-N2C(Ph)CO2Et)]

The first example of a diazo palladium adduct is reported. The complexes [(ArNHC−PPh)M(η-NC(Ph)COEt)] (M=Ni, 3; M=Pd, 4; ArNHC−PPh=3-(2,6-diisopropylphenyl)-1-[(diphenylphosphino)ethyl]imidazol-2-ylidene) were prepared by ligand exchange with styrene-coordinated precursors [(ArNHC−PPh)M(styrene)] (M=Ni, 1; M=Pd, 2). Complex 4 was fully characterized, including X-ray analyses; this constitutes the first example of a diazo adduct compound with palladium, thereby closing the gap between Groups 8 and 10 regarding this type of compounds.The authors wish to thank MINECO for financial support (CTQ2014‐52769‐C03‐01 and CTQ2011‐24502). S. G. R. thanks MINECO for a FPI fellowship