Solid state luminescence of phosphine-EWO ligands with fluorinated chalcone skeletons and their PdX2 complexes: metal-promoted phosphorescence enhancement.

Complexes trans-[PdX2L2] (X = Cl and Br), where L is 1-(PR2),2-(CHCH-C(O)Ph)-C6F4 (R = Ph, Cy, and iPr), display phosphorescent emission in the solid state, whereas due to their substantially lower lifetimes, the free ligands exhibit fluorescent behaviour. Alternatively, structurally identical derivatives with halide replaced by CN- or Pd replaced by Pt are non-emissive. DFT calculations explain this diverse behaviour, showing that the hybridization of orbitals of the MX2 moiety with those of the chalcone fragment of ligands is significant only for the LUMO of the emissive compounds. In other words, in our complexes, only MLMCT processes (LM = Metal-perturbed Ligand-centered orbital) lead to observable luminescence.

Pd/Cu bimetallic catalysis to access highly fluorinated biaryls from aryl halides and fluorinated arenes.

An efficient Pd/Cu bimetallic cross-coupling catalysis of fluoroaryl halides and fluoroarenes is reported. In situ generation of the Cu nucleophile by rate determining C-H activation of highly fluorinated aryls (≥4 F atoms) leads to high cross-coupling selectivity with little formation of homocoupling products.

Selective synthesis of fluorinated biaryls by [MCl2(PhPEWO-F)] (M = Ni, Pd) catalysed Negishi cross-coupling.

Highly selective cross-couplings to polyfluorinated assymmetric biaryls, including the symmetric biaryl C6F5-C6F5, are achieved at relatively low temperature (80 °C) and in short times using [MCl2(PhPEWO-F)] catalysts (M = Ni, Pd; PhPEWO-F = 1-(PPh2), 2-(CHCH-C(O)Ph)-C6F4), ArFI, and Zn(C6F5)2 as example of highly fluorinated nucleophile.

Easy wide scope access to luminescent fluorophosphoranes.

The almost quantitative synthesis of homologous luminescent fluorophosphoranes, by SNAr cyclization of (2'-F,2-(PR2)biaryl) phosphines made from easily accessible reagents, is reported and the DFT cyclization mechanism and alternative pathways to complete this isomerization are studied and discussed.

Ranking Ligands by Their Ability to Ease (C6F5)2NiIIL → Ni0L + (C6F5)2 Coupling versus Hydrolysis: Outstanding Activity of PEWO Ligands.

The NiII literature complex cis-[Ni(C6F5)2(THF)2] is a synthon of cis-Ni(C6F5)2 that allows us to establish a protocol to measure and compare the ligand effect on the NiII → Ni0 reductive elimination step (coupling), often critical in catalytic processes. Several ligands of different types were submitted to this Ni-meter comparison: bipyridines, chelating diphosphines, monodentate phosphines, PR2(biaryl) phosphines, and PEWO ligands (phosphines with one potentially chelate electron-withdrawing olefin). Extremely different C6F5-C6F5 coupling rates, ranging from totally inactive (producing stable complexes at room temperature) to those inducing almost instantaneous coupling at 25 °C, were found for the different ligands tested. The PR2(biaryl) ligands, very efficient for coupling in Pd, are slow and inefficient in Ni, and the reason for this difference is examined. In contrast, PEWO type ligands are amazingly efficient and provide the lowest coupling barriers ever observed for NiII complexes; they yield up to 96% C6F5-C6F5 coupling in 5 min at 25 °C (the rest is C6F5H) and 100% coupling with no hydrolysis in 8 h at -22 to -53 °C.

Fluorinated vs Nonfluorinated PR2(biaryl) Ligands and Their [AuCl(L)] Complexes: Synthesis, X-ray Structures, and Computational Study of Weak Interactions. Bond, No Bond, and Beyond.

Six fluorinated PR2(biaryl) phosphines, Ln, with R = Ph, Cy and biaryl = C6H4-C6F5, C6F4-C6H5, C6F4-C6F5, have been prepared. Their [AuCl(Ln)] complexes and H congeners with PhJohnPhos or CyJohnPhos have been studied in order to examine the interactions that bring the distal aryl close to the Au-Cl bond region. X-ray, DFT structure optimization, QTAIM, and NCI methods allow for some understanding of the forces involved. The "no bond" noncovalent distal-aryl/Au-Cl weak interactions are produced at forced short distances achieved under intramolecular structural ligand pressure. Enhanced vdW distal-aryl/Au interactions at "no bond" distances shorter than the sum of Au and C vdW radii and weaker distal-aryl/Cl interactions at "no bond" distances beyond the sum of Cl and C vdW radii counterbalance the unfavorable structural distortion of the free ligand, providing some extra stability of the molecule on the order of 2-10 kcal mol-1. The F substituents in the distal aryl induce shorter aryl distances to the Au-Cl zone, pointing overall to stronger π-aryl polarization as being mainly responsible for the NCIs with gold. The interactions in the C···Cl zone, where the distances are larger than the sum of vdW radii, contribute only about 5%, according to energy estimations using NBOs.

Hangar de hormigon armado para el aeropuerto militar de El Alto

El proyecto en cuestion constituye unicamente un calculo estructural; no incluye el estudio completo de un aeropuerto, ya que este ultimo, aparte de no estar comprendido en tema, implica una serie de problemas tecnicos que han dado lugar a una verdadera especializacion, tales como ubicacion afirmado y drenaje de pistas, vientos dominantes, circulacion, etc. el hangar se ha estudiado en base a un aeropuerto militar, no a un aeropuerto comercial para la ciudad de La Paz.