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Chvfital stated in 1972 the following conjecture: If Y~ is a hereditary hypergraph on S and .gCcy~ is a family of maximum cardinality of pairwise intersecting members of ~ , then there exists an x e S such that d~(x)=l{HeYe:xeH}l=l.al. Berge and Schrnheim proved that 1~1~1⁄2 I~el for every ~ and ~ . Now we prove that if there exists an . ~ , I~1 = [1⁄2(More)
The dinuclear molecule of the title compound, [Cd2(C6H4NO2)4(C2H8N2)2(H2O)2] 2H2O, lies on an inversion centre and forms 12-membered (CdNC3O)2 metallacycles with the two Cd ions bridged by two nicotinate ligands. Both Cd ions display coordination polyhedra with a distorted octahedral geometry that includes two pyridine N atoms from bridging and terminal(More)
The crystal structure of the title compound, [Co(C(7)H(6)NO(2)S)(2)(H(2)O)(4)], is a polymorph of the structure first reported by Du, Zhao & Wang [(2004). Dalton Trans, pp. 2065-2072]. The asymmetric unit of the title compound contains one half-mol-ecule; the Co(II) atom lies on an inversion centre in a distorted octa-hedral geometry coordinated by two N(More)
In the title compound, [Cu(C(2)H(2)ClO(2))(2)(C(8)H(7)NO)(2)(CH(4)O)], the Cu(2+) ion has a highly distorted square-bipyramidal (4 + 1 + 1) coordination environment and is bonded to three carboxyl-ate O atoms of two chloro-acetate anions (monodentate and asymmetrically bidentate), two pyridine N atoms of 2-methyl-furo[3,2-c]pyridine and one methanol O atom.(More)
The asymmetric unit of the title complex, [Cu(C(2)H(8)N(2))(2)(H(2)O)(2)](C(8)H(8)NO(2))(2)·2H(2)O, contains one anion, one half-cation and one water mol-ecule. The Cu(II) atom in the [Cu(en)(2)(H(2)O)(2)](2+) cation (en is ethyl-enediamine) lies on an inversion centre. The four N atoms of the en ligands in the equatorial plane around the Cu(II) atom form a(More)
In the title compound, [Cu(C(2)N(3))(C(10)H(8)N(2))(2)]BF(4), the Cu(II) atom shows distorted trigonal-bipyramidal geometry, with the dicyanamido ligand in the equatorial plane. The two out-of-plane Cu-N bond lengths to bipyridine are 2.006 (3) and 1.998 (3) A, whereas the in-plane Cu-N distances are 2.142 (3) and 2.043 (3) A to the bipyridine, and 2.015(More)
The asymmetric unit of the title compound, [Co(C(8)H(6)NO(2))(2)(H(2)O)(4)], contains one half-mol-ecule. The Co(II) atom lies on an inversion centre and is coordinated by two N atoms of the pyridine rings of 3-(3-pyrid-yl)acrylate anions and four O atoms of water mol-ecules in a distorted octa-hedral coordination geometry. In the crystal structure,(More)