Search results for "Cationic polymerization"
showing 10 items of 441 documents
Synthesis and X-ray structure of cationic β-diimine palladium complexes containing π-methallyl ligand
2005
High yield of cationic palladium β-diimine complexes [(CH 2 (MeCNAr) 2 )Pd(η 3 -C 4 H 7 )][Y] (Ar = C 6 H 5 , Y = PF 6 (8); 2-Me-C 6 H 4 , Y = PF 6 (9); 2,6-Me 2 -C 6 H 3 , Y = PF 6 (10); 2,6-iPr 2 -C 6 H 3 , Y = PF 6 (11), Y = B(3,5-(CF 3 ) 2 -C 6 H 3 ) 4 (12)) have been obtained by an oxidative addition of the methallyloxyphosphonium salts (5, 6) to a preformed complex Pd(dba) 2 (7) in the presence of the β-iminoamine ligands (1-4). These complexes are thermally stable and have been characterized by 'H and 1 3 C{ 1 H} NMR as well as IR spectroscopy. The structure of the cationic allyl palladium complex (12) has been solved by X-ray crystallography.
The first member of a second generation family of ligands derived from metal-ion assisted reactivity of di-2,6-(2-pyridylcarbonyl)pyridine: Synthesis…
2012
Abstract Nucleophilic attack by the carbanion −CH2COCH3 at the carbonyl carbon atoms of 2,6-di-(2-pyridylcarbonyl)pyridine, pyCOpyCOpy, in the presence of Mnn+ ions under basic conditions has yielded the cationic cluster [Mn4(OH)2(L)2(H2O)2](ClO4)4 (1), where L2− is the (py)C(CH2COCH3)(O−)(py)C(CH2COCH3)(O−)(py) dianion. The cluster cation possesses a planar {MnII2MnIII2(μ3-OH)2(μ-OR)4}4+ rhombus core, resulting from two μ3-OH− ions and two η1:η2:η1:η1:η1:η2:η1:μ3 bridging L2− groups from the in situ formed ligand. Complex 1 is antiferromagnetically coupled with an unusual S = 2 ground state resulting from spin frustration effects within the triangular Mn3 subunits of the cluster.
Average versus local structure in K2NiF4-type LaSrAlO4: direct experimental evidence of local cationic ordering
2012
The long-range ordering of a crystalline material can be accurately determined by analyzing the Bragg intensities and positions. In contrast, direct observation of short-range ordering in crystalline materials, which is increasingly considered of fundamental importance to unravel the structure-property relationships that underpin their technological applications, is a challenging task. In this study we have investigated the structure of LaSrAlO4, a representative example of compounds with the K2NiF4-type structure. By the combined use of synchrotron and neutron diffraction, pair distribution function analysis, Al-27 MQMAS NMR and atomistic simulations we have highlighted differences between…
Radical cations and dications of bis[1]benzothieno[1,4]thiazine isomers
2021
Bis[1]benzothieno[1,4]thiazines (BBTT) are particularly electron-rich S,N-heteropentacenes and their radical cations and dications can be relevant intermediates in charge transport materials. All three regioisomers of N-p-fluorophenyl-BBTT (syn–syn, syn–anti, and anti–anti) were studied. A reliable preparation of radical cations and dications using antimony pentachloride as an oxidant gives deeply colored salts. The electronic structure of the radical cations was assessed by EPR spectroscopy, whereas dicationic structures were characterized by NMR spectroscopy. In addition, a deeper insight into the electronic structure was experimentally and computationally obtained by UV/Vis spectroscopy …
Isolation of Free Phenylide-like Carbanions with N-Heterocyclic Carbene Frameworks
2009
A series of 1,3-bis(2,6-diisopropylphenyl)-5-methyl-1,3-diaza-4,6-diborabenzenes with methyl, phenyl, and dimethylamino substituents on the ring boron atoms were prepared using the cyclocondensation reaction between N,N'-bis(2,6-diisopropylphenyl)trimethylsilylformamidine and the appropriately substituted 1,1-bis(organochloroboryl)ethane, followed by deprotonation of the cationic ring intermediate. The planar, heterocyclic benzene analogues could be further deprotonated at the other ring carbon using an additional equivalent of potassium hexamethyldisilazide to yield organometallic derivatives akin to the potassium phenylide. The potassium cations could be efficiently sequestered in both so…
Surface composition analysis during the oxidation of ferrites: A necessity
1998
The cationic composition of a titanium ferrite (Fe 2.5 Ti 0.5 O 4 ) has been followed by XPS during its oxidation in cation deficient phases (without crystallographic transformation) in order to reveal a dynamic segregation phenomenon. Indeed, during this oxidation, an important modification of the chemical composition of the first layers of the material has been revealed: below 350 °C, the titanium ferrites surface becomes richer in iron and poorer in titanium. But, if the reaction is extended above 400 °C, some titanium can move to the surface. This phenomenon has been interpreted on the basis of the differences of mobility of the different ions which are present in the material. Finally,…
Anionic halide···alcohol clusters in the solid state.
2014
The cationic (1,3,5-triazapentadiene)Pt(II) complexes [1](Cl)2, [2](Cl)2, [3](Br)2, and [4](Cl)2, were crystallized from ROH-containing systems (R = Me, Et) providing alcohol solvates studied by X-ray diffraction. In the crystal structures of [1-4][(Hal)2(ROH)2] (R = Me, Et), the Hal(-) ion interacts with two or three cations [1-4](2+) by means of two or three or four contacts thus uniting stacked arrays of complexes into the layers. The solvated MeOH or EtOH molecules occupy vacant space, giving contacts with [1-4](2+), and connects to the Hal(-) ion through a hydrogen bridge via the H(1O)O(1S) H atom forming, by means of the Hal(-)···HOR (Hal = Cl, Br) contact, the halide-alcohol cluster.…
Solvent induced single-crystal to single-crystal structural transformation and concomitant transmetalation in a 3D cationic Zn(II)-framework.
2015
A 3D cationic Zn(II) framework, based on Zn2(CO2)4 paddle-wheel secondary building units (SBUs) and Zn16(CO2)32 polyhedral supramolecular building blocks (SBBs), has been synthesized. At room temperature, the framework undergoes guest solvent triggered reversible structural transformation and concomitant Zn(II) to Cu(II) transmetalation in a single-crystal to single-crystal fashion.
Cationic mono- and bi-nuclear iron complexes as Lewis acid catalysts in Mukaiyama reactions
1992
Organometallic Lewis acids derived from photolysis of mono- and bi-nuclear cationic iron carbonyl complexes function as excellent catalysts for the Mukaiyama aldol reaction.
Theoretical Insights into the Ferromagnetic Coupling in Oxalato-Bridged Chromium(III)-Cobalt(II) and Chromium(III)-Manganese(II) Dinuclear Complexes …
2012
Two novel heterobimetallic complexes of formula [Cr(bpy)(ox)(2)Co(Me(2)phen)(H(2)O)(2)][Cr(bpy)(ox)(2)]·4H(2)O (1) and [Cr(phen)(ox)(2)Mn(phen)(H(2)O)(2)][Cr(phen)(ox)(2)]·H(2)O (2) (bpy = 2,2'-bipyridine, phen = 1,10-phenanthroline, and Me(2)phen = 2,9-dimethyl-1,10-phenanthroline) have been obtained through the "complex-as-ligand/complex-as-metal" strategy by using Ph(4)P[CrL(ox)(2)]·H(2)O (L = bpy and phen) and [ML'(H(2)O)(4)](NO(3))(2) (M = Co and Mn; L' = phen and Me(2)phen) as precursors. The X-ray crystal structures of 1 and 2 consist of bis(oxalato)chromate(III) mononuclear anions, [Cr(III)L(ox)(2)](-), and oxalato-bridged chromium(III)-cobalt(II) and chromium(III)-manganese(II) din…