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Christian Näther – One of the best experts on this subject based on the ideXlab platform.
CdX2 Coordination Polymers with 2-Chloropyrazine and 2-Methylpyrazine: Similar Ligands – Similar Structures – Different ReactivityEuropean Journal of Inorganic Chemistry, 2017Co-Authors: Christian Näther, Inke Jeß, Robert E. Dinnebier, Luzia S. Germann, Michael Braun, Huayna TerraschkeAbstract:
Several coordination compounds, based on Cd halides and 2-methylpyrazine (Mepyz) or 2-Chloropyrazine (Clpyz) as N-donor coligands, are synthesized and their crystal structures determined by either single-crystal or X-ray powder diffraction (XRPD). In [CdX2(2-Clpyz)2]n (X = Cl: 1-Cl-Clpyz; X = Br: 1-Br-Clpyz; and X = I: 1-I-Clpyz) and [CdX2(2-Mepyz)2]n (X = Cl: 1-Cl-Mepyz; X = Br: 1-Br-Mepyz; and X = I: 1-I-Mepyz), the Cd cations are octahedrally coordinated by two N-donor ligands and are linked into chains by the halide anions that share common edges. In the ligand-deficient compounds [CdX2(2-methylpyrazine)]n (X = Cl: 2-Cl-Mepyz; X = Br: 2-Br-Mepyz; and X = I: 2-I-Mepyz), similar CdX2 chains, which are connected into layers by the N-donor ligands, are observed. Thermal analysis of all 1-Mepyz compounds shows a transformation into 2-Mepyz, which is not observed for the 2-Chloropyrazine compounds. On further heating, compounds of composition [(CdX2)2(2-Mepyz)]n (X = Cl: 3-Cl-Mepyz; X = Br: 3-Br-Mepyz) and [(CdI2)3(2-Mepyz)2] (4-I-Mepyz) are observed. A discrete complex, with the composition CdI2(2-Mepyz)2 monohydrate (1-I-Mepyz-H2O), and a hydrate with the composition [(CdI2)(2-Mepyz)]·1.5H2O (2-I-Mepyz-H2O) with an unknown structure, were also synthesized. Both lose the water molecules upon heating. Luminescence measurements show blue to orange emissions in the range of ca. 22530–16276 cm–1, depending on the halide or pyrazine substituent, as well as the metal halide/ligand ratio.
Synthesis, Thermal and Magnetic Properties of New Coordination Compounds based on Mn(NCS)2 with 2-Chloropyrazine and 2-Methylpyrazine as neutral Co-Ligand†Zeitschrift für anorganische und allgemeine Chemie, 2013Co-Authors: Susanne Wöhlert, Tomče Runčevski, Robert E. Dinnebier, Christian NätherAbstract:
Reaction of manganese(II) thiocyanate with 2-Chloropyrazine leads always to the formation of a compound of composition Mn(NCS)2(2-Chloropyrazine)4 (1-Mn/Cl) that consists of discrete complexes, in which the manganese cation is coordinated by two terminal thiocyanato anions and four 2-Chloropyrazine ligands. In contrast, with 2-methylpyrazine only an aqua complex of composition Mn(NCS)2(2-methylpyrazine)2(H2O)2 (1-Mn/CH3) is obtained that also consists of discrete octahedrally coordinated complexes. Moreover, a few single crystals of Mn(NCS)2(2-Chloropyrazine)4·Mn(NCS)2(2-Chloropyrazine)2(H2O)2·2-Chloropyrazine trisolvate (2-Mn/Cl) and Mn(NCS)2(2-methylpyrazine)2(H2O)2·Mn(NCS)2(H2O)4 (2-Mn/CH3) were accidently obtained but no larger amounts are available. On heating, 1-Mn/Cl and 1-Mn/CH3 transforms into new compounds of composition Mn(NCS)2(L)2 (L = 2-Chloropyrazine) (4-Mn/Cl) and 2-methylpyrazine (3-Mn/CH3). Surprisingly on further heating 1-Mn/CH3 looses additional 2-methylpyrazine ligands and transforms into a new compound of composition Mn(NCS)2(2-methylpyrazine) (4-Mn/CH3). Compound 4-Mn/Cl is isotypic to its cobalt(II) analog and 4-Mn/CH3 is isotypic to Cd(NCS)2(2-methylpyrazine) reported recently and therefore, both structures were refined by the Rietveld method. The crystal structures of both compounds are strongly related. They consists of dimeric units, in which each two manganese cations are linked by pairs of μ-1, 3-bridging thiocyanato anions, which are further connected into layers by single μ-1, 3-bridging anionic ligands. In contrast to 4-Mn/Cl, in 4-Mn/CH3 these layers are further linked into a 3D coordination network by the 2-methylpyrazine ligands. Magnetic measurements reveal that 1-Mn/Cl, 1-Mn/CH3, and 3-Mn/CH3 shows only Curie- or Curie-Weiss paramagnetism, whereas 4-Mn/Cl and 4-Mn/CH3 shows antiferromagnetic ordering at TN = 22.9 K and at 26.5 K. The results of these investigations are compared with those obtained for related compounds.
Structures and Magnetic Properties of Nickel Thiocyanato Coordination Compounds with 2‐Chloropyrazine as a Neutral ColigandEuropean Journal of Inorganic Chemistry, 2013Co-Authors: Susanne Wöhlert, Christian NätherAbstract:
Reaction of Ni(NCS)2 with 2-Chloropyrazine in different molar ratios and solvents at room temperature leads to five new coordination polymers. In the crystal structures of Ni(NCS)2(2-Chloropyrazine)4·2-Chloropyrazine solvate (1) and Ni(NCS)2(2-Chloropyrazine)4 (2) the nickel cations are octahedrally coordinated by two terminal N-bonded thiocyanato anions and four 2-Chloropyrazine ligands into discrete complexes. In the crystal structures of the Ni(NCS)2(2-Chloropyrazine)2(CH3OH)2·(CH3OH)2 solvate (3) and Ni(NCS)2(2-Chloropyrazine)2(CH3OH)2 (4) each nickel(II) cation is coordinated by two terminal N-bonded thiocyanato anions, two 2-Chloropyrazine ligands and two O-bonded methanol molecules in a slightly distorted octahedron. On heating, compounds 1 and 2 transform into the ligand-deficient 1:2 compound 5, which can also be crystallized from solution. In the crystal structure of [Ni(NCS)2(2-Chloropyrazine)2]n (5) each nickel(II) cation is coordinated by two N-bonded and two S-bonded thiocyanato anions as well as two 2-Chloropyrazine ligands. The nickel cations are linked into dimers by pairs of μ-1,3-bridging thiocyanato anions that are further linked into chains and finally into layers by single μ-1,3-bridging thiocyanato anions. Magnetic measurements of compound 1 and 2 show only Curie or Curie–Weiss paramagnetism, whereas in the ligand-deficient compound 5 a metamagnetic transition is observed at a critical field of HC = 14 kOe. The results of the magnetic measurements are compared with those of related nickel compounds with different coligands.
Fabrice Cottet – One of the best experts on this subject based on the ideXlab platform.
Silyl‐Mediated Halogen/Halogen Displacement in Pyridines and Other HeterocyclesEuropean Journal of Organic Chemistry, 2002Co-Authors: Manfred Schlosser, Fabrice CottetAbstract:
Heating with bromotrimethylsilane converts 2-chloropyridine into 2-bromopyridine and 2-chloro-6-methylpyridine into 2-bromo-6-methylpyridine. Both 2-chloropyridines and 2-bromopyridines give the corresponding iodo compd. when treated with in situ generated iodotrimethylsilane. Although 3- and 4-chloropyridine are completely inert, 2,4-dichloropyridine undergoes the halogen/halogen exchange simultaneously at the 2- and 4-position. Halogen displacement takes place exclusively at the 2-position with 2,3-dichloropyridine and 2,5-dichloropyridine. In agreement with the intermediacy of N-trimethylsilylpyridinium salts as a prerequisite for the occurrence of halogen exchange, neither 2-fluoropyridine and 2-fluoro-6-methylpyridine nor any 2,6-dihalopyridine reacts. Finally, bromine/chlorine and iodine/chlorine substitution can also be accomplished with 2- or 4-chloroquinoline, 1-chloroisoquinoline, 2-chloropyrimidine, chloropyrazine, and 2,3-dichloroquinoxaline as substrates. [on SciFinder (R)]
Li Yu-tao – One of the best experts on this subject based on the ideXlab platform.
Synthesis of 3-oxo-3-[3-trifluoromethyl-5,6-dihydro[1,2,4]triazolo[4,3-a] pyrazin-7(8H)-yl]-1-phenylpropan-1-amineChemical Research and Application, 2009Co-Authors: Li Yu-taoAbstract:
The fused triazole derivatives,which is an important inhibitors of the dipeptidyl peptidase-Ⅳ enzyme(DPP-Ⅳ),can be used for the treatment or prevention of type 2 diabetes.A new fused triazole derivatives of 3-oxo-3-[3-trifluoromethyl-5,6-dihydro[1,2,4]-triazolo[4,3-a]pyrazin-7(8H)-yl]-1-phenylpropan-1-amine was synthesized from 2-Chloropyrazine and benzaldehyde by hydrazinolysis,trifluoroacetylation,cyclization,hydrogenation,condensation and deprotection reaction.The structures of the compound and its intermediates were determined by IR,NMR,and MS.
Synthesis and Characterization of 7-(3-amino-3-(4-methoxyphenyl)propanoyl)-3-(trifluoromethyl)-5,6,7,8-tetrahydro[1,2,4]triazolo[4,3-α]piperazineJournal of Nanchang University, 2009Co-Authors: Li Yu-taoAbstract:
The fused triazole derivatives,which is an important inhibitors of the dipeptidyl peptidase-Ⅳ enzyme(DPP-Ⅳ inhibitors),can be used for the treatment or prevention of type 2 diabetes.A new fused triazole derivatives of 7-(3-amino-3-(4-methoxyphenyl)propanoyl)-3-(trifluoromethyl)-5,6,7,8-tetrahydro[1,2,4] triazolo[4,3-α]piperazine was synthesized from 2-Chloropyrazine and 4-methoxy-benzaldehyde by hydrazinolysis,trifluoroacetylation,cyclization,hydrogenation,condensation and deprotection reaction.The structures of the titled compound and intermediates were determined by IR,NMR,and MS.