The magnetic properties of the compound of the formula Cu(2-pca)2, (2-pca = 2-picolinate ion) were studied in the light of its known X-ray structure. The crystal structure consists of a copper atom lying in the centre of symmetry, trans square-planar coordinated via two pyridine nitrogens and the carboxylate oxygen atoms of the two picolinate anions. The crystal packing is due to short pi-pi stacking interactions between pyridine rings belonging to different molecules giving rise to a one-dimensional polymeric network arrangement. Additional CH-O hydrogen bonds form a three-dimensional polymeric network. The variable-temperature (1.8-300 K) magnetic susceptibility data of the complex were interpreted with the Bonner-Fisher expression with molecular field approximation, yielding J, zJ' and g values of -0.76, -0.47 cm-1, 2.09, respectively. The magnitude of the magnetic interaction through the pi-pi stacking interaction and hydrogen bond, and the nature of the exchange coupling is discussed on the basis of the structural data results.
A new method of synthesis of bicyclic gamma-lactones with the methyl- or gem-dimethylcyclopropane system from gamma,delta unsaturated esters is described. The reaction of gamma-halo delta- lactones with DBU is the key step of this synthesis. The mechanism of the dehydrohalogenation- cyclization process of gamma-halo-delta-lactones is proposed. The structures of products were confirmed by both spectroscopic and crystallographic methods.
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This brief review discusses the coordination behaviour of π-coordinated copper(I) in the structures of [Cu2(μ-dapp)(NH2SO3)4]·2H2O (1), [C4H12N2][Cu2(μ-dapp)(NH2SO3)6]·2H2O (2), [Cu2(μ-dapp)(H2O)6] (SiF6)2·2H2O (3), [Cu2(μ-dapp)(NO3)4(H2O)2]·2H2O (4), [Cu(μ-ahmta)(NO3)(H2O)](NO3)·H2O (5), and [Cu(μ-ahmta)(H2O)2](BF4)2·H2O (6) complexes (dapp = N,N′-diallylpiperazinium(2+), ahmta = N-allylhexamethylenetetraminium), obtained as single crystals by means of an alternating current electrochemical technique. The above π-complexes are formed respectively by CuSO3NH2, Cu2SiF6, CuNO3, and CuBF4 salts, unknown in a free state.
The first crystal structure involving Schiff base containing 4-substituted 1,2,4-triazolium cation is reported. The neutral (4-chloro-benzylidene)-[1,2,4] triazol-4-yl-amine (T) and protonated (HT+) molecules are connected by the strong [N-H...N]+ hydrogen bond forming the discrete dimers. The pair of the dimers and two BF4 _ ions are linked via the weak C-H...F interactions and create tetrameric units. BF4 _ ions mediate between succeeding tetramers and as a result double ribbons along [110] are formed. No intermolecular, directional interactions between neighbour ribbons in the crystal were found.
D-Hydroxy-G-lactones and G-hydroxy-D-lactones were synthesized from acyclic isoprenoid G,D-epoxy esters in acid induced lactonization. The reaction course was depended on the acidic agent applied. The mechanism of lactonization is presented.
The 3-cyclohexene-1-carboxylic acid was prepared and resolved with brucine. Absolute configuration of (R)-(+)-3-cyclohexene-1-carboxylic acid was confirmed by X-ray diffraction methods.
1,2:3,4,5,6-Tri-O-isopropylidene-D-gluconate (1) undergoes the beta-elimination reaction in the presence of LDA to afford 3-deoxy-1,2:5,6-di-O-isopropylidene-D-erythro-hex-3-enolactone (6). Attempts to prepare the phosphonate 4 by reaction of 1 with dimethyl methylphosphonate in the presence of LDA failed; only elimination product 6 was isolated from the reaction mixture. The sugar phosphonate 8 (protected form of 4) was prepared from methyl 2-O-benzyl-3,4:5,6-di-O-isopropylidene gluconate (7) by reaction with (-)CH2P(O)(OMe)2. The crystal structure of 1 is reported.
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