Search results for "Lewis base"
showing 4 items of 4 documents
DFT analysis of titanium complexes with oxygen-containing bidentate ligands
2003
Strength of the TiO co-ordinate bond in several titanium complexes with bidentate ligands has been investigated by means of DFT. Mutual interaction of particular donors and their influence on Lewis acidity of the central atom have also been studied. The energy of ligand binding ranges from −19 to −454 kJ/mol, depending on the kind of donors. Calculations confirm that a strong donor, alkoxide anion, co-ordinatively saturates the titanium and makes binding of new ligands less exoenergetic. On the contrary, two oxygen atoms of similar donor number do not have much influence on each other. Strength of the TiO bonds in titanium complexes with certain oxygen-containing bidentate ligands has bee…
Carbon’s Three-Center-Four-Electron Tetrel Bond, Treated Experimentally
2018
Tetrel bonding is the noncovalent interaction of group IV elements with electron donors. It is a weak, directional interaction that resembles hydrogen and halogen bonding yet remains barely explored. Herein, we present an experimental investigation of the carbon-centered, three-center, four-electron tetrel bond, [N−C− N]+ , formed by capturing a carbenium ion with a bidentate Lewis base. NMRspectroscopic, titration-calorimetric, and reaction-kinetic evidence for the existence and structure of this species is reported. The studied interaction is by far the strongest tetrel bond reported so far and is discussed in comparison with the analogous halogen bond. The necessity of the involvement of…
Rola chlorku magnezu jako nośnika katalizatorów Zieglera-Natty
2000
Structural examination data are presented for various supports. Porosimetry (Table 2) and particle size distribution studies on MgCl 2, MgCl 2(THF) 2, Al 2O 3 as supports, carried out prior to and after ball-milling (Figs. 1, 3), suggest that MgCl 2 is beneficial as carrier because it is more liable to pretreatment (ball-milling, presence of a Lewis base) and allows its mass to be better utilized and its surface to produce catalytically active centers. Prolonged ball-milling of MgCl 2 was found to result not only in comminuted particles but also in increased specific area and larger pore volume. Studies on synthesis conditions of a vanadium precursor supported on MgCl 2(THF) 2 showed prolon…
(Co-)solvent selection for single-wall carbon nanotubes: best solvents, acids, superacids and guest-host inclusion complexes.
2011
Analysis of 1-octanol-water, cyclohexane-water and chloroform (CHCl(3))-water partition coefficients P(o-ch-cf) allows calculation of molecular lipophilicity patterns, which show that for a given atom log P(o-ch-cf) is sensitive to the presence of functional groups. Program CDHI does not properly differentiate between non-equivalent atoms. The most abundant single-wall carbon nanotube (SWNT), (10,10), presents a relatively small aqueous solubility and large elementary polarizability, P(o-ch-cf) and kinetic stability. The SWNT solubility is studied in various solvents, finding a class of non-hydrogen-bonding Lewis bases with good solubility. Solvents group into three classes. The SWNTs in so…