Stabilization of a Two-Coordinate [GeCl]⁺ Cation by Simultaneous σ and π Donation from a Monodentate Carbodiphosphorane

Give me four: The synthesis, structure, and reactivity of [GeCl]+ and [SnCl]+ cations bearing a carbodiphosphorane as ancillary ligand are presented. In the Ge compound, simultaneous σ and π donation from the carbodiphosphorane to Ge is observed (see HOMO (left) and HOMO−1 (right); C black, H white, P orange, Cl green, Ge purple (not visible)), whereas only the σ dative component is present in the Sn analogue

Carbon-Based Frustrated Lewis Pairs

The use of FLPs offers a new and versatile strategy to activate small molecules such as H2, CO2, acetylenes, disulfides, olefins, and nitrogen oxides. This chapter describes the recent advances reported on the design and reactivity of new frustrated systems constituted by at least one carbon-based partner

Synthesis, Structure, and Applications of Pyridiniophosphines

A new family of cationic ligands, N-alkyl/aryl pyridiniophosphines, has been synthesized through a short, scalable, and highly modular route. Evaluation of their electronic properties evidenced weak σ-donor and quite strong π-acceptor character when used as ancillary ligands. These attributes confer a substantially enhanced π-acidity to the PtII and AuI complexes thereof derived and, as result, they depict an improved ability to activate alkynes towards nucleophilic attack. This superior performance has been demonstrated along several mechanistically diverse PtII- and AuI-catalyzed transformations

Polyfluorinated Cyclopentadienones as Lewis Acids

The ability of 2,3,4,5-tetrakis(trifluoromethyl)cyclopenta-2,4-dien-1-one and 2,3,4,5-tetrakis(pentafluorophenyl)cyclopenta-2,4-dien-1-one to act as organic Lewis acids in the field of frustrated Lewis pair (FLP) chemistry was evaluated. Whereas the former ketone formed zwitterionic adducts with all phosphines studied, the latter did not react with bulky phosphines and, instead, gave completely organic FLPs. Unfortunately, these did not activate dihydrogen, even under high pressures

Coordination Chemistry of Ene-1,1-diamines and a Prototype "Carbodicarbene"

Carbophilic Lewis acids can polarize a coordinated π-bond by a slippage mechanism. A series of stable ylid- or enolate gold complexes of ene-1,1-diamines not only emulate this property, but also reveal the exceptional donor capacity of such electron-rich olefin ligands. Moreover, the first metal complex of a tetraaminoallene is reported, which features a prototype “carbodicarbene” ligand bound to a transition-metal template

Tuning the Lewis Acidity of Boranes in Frustrated Lewis Pair Chemistry: Implications for the Hydrogenation of Electron-Poor Alkenes

An analysis of the metal-free reduction of electron deficient olefins by frustrated Lewis pairs indicates that the rate-determining step might be either the heterolytic cleavage of H2 to form an -onium borohydride salt, or the subsequent transfer of the hydride moiety to the substrate following a Michael-type addition reaction. While the use of strong Lewis acids such as B(C6F5)3 facilitates the first of these processes, hydride transfer to the olefin should be contrarily favoured by the use of weak Lewis acids which, for this very same reason, might be unable to promote the prior H2 split. After systematic testing of several boranes of different Lewis acidity (assessed by using the Childs’ method) and steric demand, an optimal situation that employs tris(2,4,6-trifluorophenyl)borane was reached. Mixtures of this borane with 1,4-diazabicyclo[2.2.2]octane (DABCO) exhibited excellent catalytic activity for the hydrogenation of alkylidene malonates. In fact, this transformation could be achieved under milder conditions than those we reported previously. Moreover, the reaction scope could be expanded to other electron deficient olefins containing esters, sulfones or nitro functionalities as electron-withdrawing substituents

Steering the Surprisingly Modular π-Acceptor Properties of N-Heterocyclic Carbenes: Implications for Gold Catalysis

Thumbnail image of graphical abstract Accept it! Although the π-acceptor properties of N-heterocyclic carbenes (NHCs) are often considered negligible, they can be enhanced to the extent that they start to dominate the catalytic behavior of gold–NHC complexes (see scheme). As it seems to be easier to tune the π acidity of NHCs than to alter their σ-donor properties, the general perception of this important class of ancillary ligands needs to be revised

Estrategias de marketing educativo para el posicionamiento de la institución educativa privada Inmaculada Bilingüe - 2018

Este proyecto de investigación surge de la necesidad de mejorar las estrategias de marketing educativo de la institución educativa privada la Inmaculada Bilingüe, debido a que el colegio no ha logrado el posicionamiento adecuado en la región, por muchos factores importantes como son, la calidad del servicio, la falta de exposición de atributos diferencial. Como objetivo fue proponer una mejora de estrategias de marketing educativo para lograr el posicionamiento de la institución privada la Inmaculada Bilingüe – 2018. La investigación es de tipo descriptivo y propositivo, el diseño es no experimental y cuantitativo, la población es de 1659 padres de familia con una muestra de 313, donde la información se obtuvo mediante una encuesta con 23 premisas y con alternativas con respecto a la escala de Likert. Se concluye que las estrategias de marketing educativo que se emplean en la institución educativa privada la Inmaculada Bilingüe no son las idóneas para la captación de nuevos clientes, ya que no cuentan con un área de marketing específico, siendo algunos docentes los que desarrollan la labor de una forma empírica, estando al tanto de esta problemática los padres de familia que según la encuesta el 45.4% afirma que el servicio de calidad es regular.TesisGestión empresarial y emprendimient

On the Reactivity of Tetrakis(trifluoromethyl)cyclopentadienone towards Carbon-Based Lewis Bases

The reactivitiy of tetrakis(trifluoromethyl)cyclopentadienone towards different C-based Lewis bases, such as N-heterocyclic carbenes (NHC), ylides and isonitriles, are reported. While sterically not hindered carbenes were found to yield kinetic adducts by regiospecific nucleophilic attack at the position adjacent to the carbonyl group of the ketone, bulkier nucleophiles afforded the thermodynamically more stable O-bridged zwitterions. Interestingly, isonitriles were found to dimerize and trimerize under the same reaction conditions, forming bicyclic products that evolve differently depending on the nature of the substituents