Search results for "mer"
showing 10 items of 29660 documents
Synthesis of copper(II) and gold(III) bis(NHC)-pincer complexes
2016
Abstract CuII and AuIII chlorido complexes bearing the bis(NHC) carbazolide pincer ligand (bimca) were synthesized by transmetallation from the respective lithium complex [Li(bimca)] (NHC=N-heterocyclic carbene). In the case of copper, two different molecular structures were obtained depending on the copper source. With Cu(II) chloride the paramagnetic mononuclear [Cu(bimca)Cl] complex is formed and has been characterized by EPR spectroscopy and X-ray structure analysis, while copper(I) chloride leads under oxidation to a dinuclear structure in which two cationic [CuII(bimca)] moieties are bridged by one chlorido ligand. The positive charge is compensated by the [CuCl2]− counter ion, as pro…
Soluble Heterometallic Coordination Polymers Based on a Bis-terpyridine-Functionalized Dioxocyclam Ligand
2010
Soluble homo- and heterometallic coordination polymers containing transition metal cations (Cu(2+), Fe(2+), Co(2+), and Ni(2+) ions) were prepared in a two-step procedure using a polytopic bis(terpyridine)dioxocyclam ligand 1H(2) (dioxocyclam = 1,4,8,11-tetraazacyclotetradecane-5,7-dione). These supramolecular systems incorporate two different metal complexes, the metal cations being located both between two terpyridine units and in the macrocyclic framework. The characterization of these soluble architectures was investigated by cyclic voltammetry, mass spectrometry, viscosimetry, and UV-vis absorption and electron paramagnetic resonance (EPR) spectroscopies. Our results clearly indicate t…
An Entry to Mixed NHC-Fischer Carbene Complexes and Zwitterionic Group 6 Metal Alkenyls
2016
The addition of NHCs to α,β-unsaturated Cr(0) and W(0) (Fischer) carbene complexes is strongly dependent on the electrophilicity of the carbene carbon. Electrophilic alkoxy-carbene complexes quantitatively react with NHCs to yield stable zwitterionic (racemic) Cr(0) - and W(0) -alkenyls with total regio- and E-stereoselectivity. Less electrophilic aminocarbenes react with NHCs to promote the displacement of a CO ligand and yield "mixed" NHC/Fischer biscarbenes in a process that is unprecedented in group 6 metal-carbene chemistry. In fact, the compounds prepared, are some of the scarce examples of Fischer bisylidenes reported in the literature. The electrochemistry of the zwitterionic Cr(0) …
Isomerisation of Liquid-Crystalline Tristriazolotriazines
2017
Star-shaped discotic liquid crystals with columnar superstructures constitute a highly interesting class of organic materials. Phenyl-substituted tris[1,2,4]triazolo-[1,3,5]triazine, prepared by a Huisgen reaction of phenyltetrazole and cyanuric chloride, represents an excellent core for discotic liquid crystals (DLCs). The thermal stability is not perfect, at temperatures above the clearing point, a successive threefold isomerization leads to a highly planar, C
Self-assembly of M4L4tetrahedral cages incorporating pendant PS and PSe functionalised ligands
2019
Herein, the synthesis of metal–organic tetrahedral cages featuring flexible thio- and selenophosphate-based ligands is described. The cages were prepared by sub-component self-assembly of AP(OC6H4NH2-4)3 (A = S, Se) or SP(SC6H4NH2-4)3, 2-pyridinecarboxaldehyde, and either Fe[BF4]2 or Co[BF4]2. Preliminary host–guest studies into the ability of the pendant PS and PSe groups to interact with suitable substrates will be discussed.
Reactivity of [1,2,3]Triazolo[1,5-a]pyridines as 1,3-dipoles
2016
Abstract We have studied the reactions between [1,2,3]Triazolo[1,5- a ]pyridines 1a,b,c and electron-deficient ethylenes in different conditions. Compounds 1a and 1b react with ethyl propiolate, and dimethyl acetylene dicarboxylate giving a new class of biaryl compounds pyridyl pyrazoles, and with ethyl acrylate giving pyridyl cyclopropanes. Compound 1c did not give any product in the studied conditions. A proposal of mechanism of these reactions is done in which the triazolopyridines act as 1,3-dipoles giving 1,3-dipolar cycloadditions.
Regioselective Synthesis of Mono- and Dispiropyrazoline Derivatives via 1,3-dipolar Cycloaddition with Nitrilimines
2016
The 1,3-dipolar cycloaddition reaction of (E,E)-1,3-bis(arylidene)indan-2-one with diarylnitrilimines, generated in situ via dehydrohalogenation of the corresponding hydrazonoyl chlorides , affords predominantly monospiropyrazolines and as a mixture of diastereoisomers. Also dispiropyrazolines are formed in moderate yields. The structure and stereochemistry of cycloadducts were confirmed by 1H and 13C-NMR spectroscopy, elemental analyses data, and single-crystal X-ray diffraction studies of and .
Synthesis of substituted piperidines by enantioselective desymmetrizing intramolecular aza-Michael reactions.
2018
An organocatalytic enantioselective intramolecular aza-Michael reaction has been described for the first time in a desymmetrization process employing substrates different from cyclohexadienones. By using 9-amino-9-deoxy-epi-hydroquinine as the catalyst and trifluoroacetic acid as a co-catalyst, a series of enantiomerically enriched 2,5-and 2,6-disubstituted piperidines have been obtained in good yields and with moderate diastereoselectivity. Depending on the catalyst/co-catalyst loading ratio, either the major or the minor diastereoisomer of the final piperidine products was achieved with high levels of enantioselectivity. Finally, some mechanistic insights have been considered by means of …
Regioselective Bromination and Functionalization of Dibenzo[hi,st]ovalene as Highly Luminescent Nanographene with Zigzag Edges.
2019
Dibenzo[hi,st]ovalene (DBOV) is a nanographene with a combination of zigzag and armchair edges, consisting of 38 sp2 carbons. Excellent optical properties with strong red emission have been demonstrated. Here we report the regioselective bromination of DBOV bearing two mesityl groups (DBOV-Mes) by treatment with N-bromosuccinimide (NBS) under mild conditions. The dibrominated DBOV was further subjected to transition-metal-catalyzed cross-coupling reactions, that is, Suzuki and Sonogashira coupling, demonstrating the edge-decoration of DBOV with different functional groups. Notably, DBOVs arylated at the bay regions showed intense red emission and enhanced fluorescence quantum yields of up t…
Interactions of a Diplumbyne with Dinuclear Transition Metal Carbonyls to Afford Metalloplumbylenes
2020
The metathesis reactions of the diplumbyne AriPr6PbPbAriPr6 (AriPr6 = −C6H3–2,6-(C6H2–2,4,6-iPr3)2) with the dinuclear metal carbonyls Mn2(CO)10, Fe2(CO)9, and Co2(CO)8 under mild conditions afforded the complexes Mn(CO)5(PbAriPr6) (1), Fe(CO)4(PbAriPr6)2 (2), and Co4(CO)9(PbAriPr6)2 (3), respectively. Complexes 1–3 were structurally characterized by single-crystal X-ray diffraction and spectroscopically characterized by 1H, 13C{1H}, 59Co{1H}, and 207Pb{1H} NMR; UV–vis; and IR methods. They are rare examples of species formed by the direct reaction of a group 14 dimetallyne with transition metal carbonyls. Complexes 1 and 2 feature Mn–Pb or Fe–Pb single bonds, whereas in 3 a Co–Pb cluster i…