Search results for "periodic table"
showing 10 items of 262 documents
Preparation and crystal structure of the oxalato-bridged CrIII–AgItwo-dimensional compound {Ag3(H2O)[Cr(dpa)(ox)2]3}n·2nH2O (dpa = 2,2′-dipyridylamin…
2004
The reaction of the mononuclear complex [Cr(dpa)(ox)2]− (dpa = 2,2-dipyridylamine) with Ag+ in aqueous solution affords the two-dimensional compound {Ag3(H2O)[Cr(dpa)(ox)2]3}n·2nH2O (1) whose structure has been determined by single-crystal X-ray diffraction. Six crystallographically independent metal atoms (three chromium and three silver atoms) occur in 1. The three [Cr(dpa)(ox)2]− units in 1 act as ligands towards the silver atoms through the two oxalate groups. Each oxalate group acts as bridging ligand adopting five coordination modes: bis-bidentate, bis-bidentate/monodentate (outer), bis-bidentate/monodentate (inner), bidentate/bis-monodentate (outer) and bidentate/monodentate (outer).…
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. NMR-spectroscopic, 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 …
ChemInform Abstract: Synthesis of Sesquiterpenes via Silicon-Guided Rearrangement of Epoxydecalins
2009
A survey of the rearrangement of methyldecalins via C-5 carbocation intermediates, with special attention to the silicon-guided rearrangement of epoxydecalins is provided. A TMS group properly posi...
Kritische Bemerkungen zur Entwicklung des Sapienstypus
1953
The earliest hominid predecessors as yet known, the Australopithecines, show that the branch leading to man was separated from the group of the anthropoids as early as the Tertiary. The Australopithecines as a group show great variability. The group contains in its genetic make-up all the characteristics of the representatives of the later stages. The presence of the primitive forms of many human characteristics has led us to include in the human line of evolution only those types which have remained primitively human (Australopithecus, Steinheim, Swanscombe, Fontechevade, Piltdown).Pithecanthropus and Neanderthals are not to be considered as stages of a higher evolution but as sidebranches…
Approaches for the introduction of fluorinated substituents into [1,2,3]Triazolo[1,5-a]pyridines
2014
Abstract [1,2,3]Triazolo[1,5-a]pyridines functionalization with a trifluoromethyl group has been achieved for the first time using different synthetic strategies. Furthermore, these scaffolds have been employed as starting material in the synthesis of new 2,6-disubstituted pyridines containing the trifluoromethyl group, compounds that are not available using other methodologies. A fluorine-mediated triazolopyridine dimerisation is described, improving the previously known synthetic method. Preliminary studies focused on exploring triazolopyridines reactivity with electrophilic fluorine have revealed a new approach for the obtainment of imidazopyridines.
Structure and photoreactivity of stable zwitterionic group 6 metal allenyls
2013
The synthesis and mechanistic study of the unprecedented reactivity of a series of zwitterionic η(1)-metal allenyls are reported.
A spin-crossover complex based on a 2,6-bis(pyrazol-1-yl)pyridine (1-bpp) ligand functionalized with a carboxylate group
2014
Combining Fe(ii) with the carboxylate-functionalized 2,6-bis(pyrazol-1-yl)pyridine (bppCOOH) ligand results in the spin-crossover compound [Fe(bppCOOH)2](ClO4)2 which shows an abrupt spin transition with a T1/2 of ca. 380 K and a TLIESST of 60 K due to the presence of a hydrogen-bonded linear network of complexes.
Block copolymers from ionic liquids for the preparation of thin carbonaceous shells
2017
This paper describes the controlled radical polymerization of an ionic-liquid monomer by RAFT polymerization. This allows the control over the molecular weight of ionic liquid blocks in the range of 8000 and 22000 and of the block-copolymer synthesis. In this work we focus on block copolymers with an anchor block. They can be used to control the formation of TiO2 nanoparticles, which are functionalized thereafter with a block of ionic-liquid polymer. Pyrolysis of these polymer functionalized inorganic nanoparticles leads to TiO2 nanoparticles coated with a thin carbonaceous shell. Such materials may, e.g., be interesting as battery materials.
Preparation and structural studies on dibutyltin(IV) complexes with pyridine mono- and dicarboxylic acids
2004
Abstract A number of organotin(IV) complexes with pyridine mono- and dicarboxylic acids (containing ligating –COOH group(s) and aromatic {N} atoms) were prepared in the solid state. The bonding sites of the ligands were determined by means of FT-IR spectroscopic measurements. It was found that in most cases the –COO− groups form bridges between two central {Sn} atoms, thereby leading to polymeric (oligomeric) complexes. On this basis, the experimental 119Sn Mossbauer spectroscopic data were treated with partial quadrupole splitting approximations. The calculations predicted the existence of complexes with octahedral (oh) and trigonal-bipyramidal (tbp) structures, but the formation of comple…
ChemInform Abstract: New Polymorph of InVO4: A High-Pressure Structure with Six-Coordinated Vanadium.
2014
High-pressure XRD and Raman spectroscopy on orthorhombic InVO4 (space group Cmcm, Z = 4) reveal the existence of a new wolframite-type polymorph of InVO4 near 7 GPa.