Solid State Structures of Alkali Metal Ion Complexes Formed by Low-Molecular-Weight Ligands of Biological Relevance.

This chapter provides structural data, mainly metal binding sites/modes, observed in crystal structures of alkali metal ion complexes containing low-molecular-weight ligands of biological relevance, mostly obtained from the Cambridge Structural Database (the CSD version 5.35 updated to February 2014). These ligands include (i) amino acids and small peptides, (ii) nucleic acid constituents (excluding quadruplexes and other oligonucleotides), (iii) simple carbohydrates, and (iv) naturally occurring antibiotic ionophores. For some representative complexes of these ligands, some details on the environment of the metal coordination and structural characteristics are described.

Synthesis and characterization of the titanium complexes bearing two ß-enaminoketonato ligands with electron withdrawing groups/modified phenyls and their behaviors for ethylene (co-)polymerization.

A series of new titanium complexes with two asymmetric bidentate ß-enaminoketonato [N,O] ligands (2b-t), [PhN=C(CF(3))CHC(Ar)O](2)TiCl(2) (2b, Ar = -C(6)H(4)F(o); 2c, Ar = -C(6)H(4)F(m); 2d, Ar = -C(6)H(4)F(p); 2e, Ar = -C(6)H(4)Cl(p); 2f, Ar = -C(6)H(4)OMe(p); 2g, Ar = -C(6)H(4)CF(3)(p); 2h, Ar = -C(6)H(4)CF(3)(m); 2i, Ar = -C(6)H(4)CF(3)(o); 2j, Ar = -C(6)H(4)Cl(o); 2k, Ar = -C(6)H(4)Br(o); 2l, Ar = -C(6)H(4)I(o); 2m, Ar = -C(6)H(3)F(2)(2,4); 2n, Ar = -C(6)H(3)F(2)(2,6); 2o, Ar = -C(6)H(3)F(2)(3,4); 2p, Ar = -C(6)H(3)F(2)(3,5); 2q, Ar = -C(6)F(5); 2r, Ar = C(6)F(4)OMe; 2s, Ar = -C(6)H(3)Cl(2)(2,6); 2t, Ar = -C(6)H(3)Cl(2)(2,5)), have been synthesized based on substituted acetophenones. X-Ray analyses reveal that complexes 2h, 2k, 2m, and 2n adopt distorted octahedral geometry around the titanium center, in which the two chloride ligands are situated in the cis-orientation. 2s also adopts distorted octahedral geometry, but the two chloride ligands in it are situated in the trans-orientation due to the increase of the steric effect of the phenyl derived from the acetophenone. The influence of the substituent effects on catalyst performance, including catalytic activities and the molecular weight distribution of the polymers obtained, was investigated in detail. With modified methylaluminoxane (MMAO) as a cocatalyst, complexes 2b-r and 2t are active catalysts for ethylene polymerization at room temperature, and produce high molecular weight polymers. It is observed that the catalytic activities are significantly enhanced by introducing some electron-withdrawing groups, such as -F, -Cl and -CF(3), into the suitable positions of the phenyl ring close to the oxygen donor. It should be noted that complexes 2c-i, 2p, 2n and 2t are also capable of promoting the living copolymerization of ethylene with norbornene at room temperature, yielding high molecular weight copolymers with narrow molecular weight distributions (PDI = 1.05-1.30).

Novel vanadium(III) complexes with bidentate N,N-chelating iminopyrrolide ligands: synthesis, characterization and catalytic behaviour of ethylene polymerization and copolymerization with 10-undecen-1-ol.

A series of novel vanadium(III) complexes bearing iminopyrrolide chelating ligands [2-(RN=CH)C4H3N]V(THF)2Cl2 (2a: R = cyclohexyl; 2b: R = Ph; 2c: R = 2,6-iPr2C6H3; 2d: R = p-CF3C6H4; 2e: R = C6F5) have been synthesized and characterized. Single-crystal X-ray diffraction revealed that complexes 2a, 2c and 2e adopt an octahedral geometry around the vanadium center. In the presence of Et2AlCl as a co-catalyst, these complexes displayed high catalytic activities up to 48.6 kg PE mmol(V)(-1) h(-1) bar(-1) for ethylene polymerization, and produced high molecular weight polymers. 2a-e/Et2AlCl catalytic systems were tolerant to elevated temperature (70 degrees C) and yielded unimodal polyethylenes, indicating the single site behaviour of these catalysts. By pre-treating with equimolar amounts of alkylaluminums, functional alpha-olefin 10-undecen-1-ol can be efficiently incorporated into polyethylene chains. 10-Undecen-1-ol incorporation can easily reach 15.8 mol% under the mild conditions. When compared with VCl3(THF)3 or rac-Et[Ind]2ZrCl2, these vanadium(III) complexes exhibited higher activities towards the copolymerization, and can incorporate more 10-undecen-1-ol into polymer chains under the similar conditions.

catena-Poly[diammonium [diaqua-bis(pyridine-2,4-dicarboxyl-ato-κN,O)cuprate(II)] [[diaqua-copper(II)]-µ-pyridine-2,4-dicarboxyl-ato-κN,O:O-[tetra-aqua-cadmium(II)]-µ-pyridine-2,4-dicarboxyl-ato-κO:N,O] hexa-hydrate].

The title mixed-metal complex, {(NH(4))(2)[Cu(C(7)H(3)NO(4))(2)(H(2)O)(2)][CdCu(C(7)H(3)NO(4))(2)(H(2)O)(6)]·6H(2)O}(n), contains one octa-hedrally coordinated Cd(II) center and two octa-hedrally coordinated Cu(II) centers, each lying on an inversion center. The two Cu(II) atoms are each coordinated by two O atoms and two N atoms from two 2,4-pydc (2,4-H(2)pydc = pyridine-2,4-dicarboxylic acid) ligands in the equatorial plane and two water mol-ecules at the axial sites, thus producing two crystallographically independent [Cu(2,4-pydc)(2)(H(2)O)(2)](2-) metalloligands. One metalloligand exists as a discrete anion and the other connects the Cd(H(2)O)(4) units, forming a neutral chain. O-H⋯O and N-H⋯O hydrogen bonds connects the polymeric chains, complex anions, ammonium cations and uncoordinated water mol-ecules into a three-dimensional supra-molecular network.

Synthesis and characterization of binuclear molybdenum-polycarboxylate complexes with sulfur bridges.

A group of four binuclear sulfur-bridged molybdenum-polycarboxylato complexes with homocitrate, citrate, cysteine, ethylenediaminetetraacetate ligands, respectively, have been synthesized and characterized. These complexes were prepared in order to study the interaction of Mo and homocitrate in the FeMo-co of nitrogenases. In the structures of K4(NH4)2[Mo2O2S2(C6H4O7)2].10H2O (2), (NH4)2[Mo2O2S2(C3H5SNO2)2].5H2O (3) and (NH4)2[Mo2O2S2(C10H12N2O8)].3.5H2O (4), molybdenum (V) atom adopts a distorted octahedral arrangement through a terminal oxygen atom, two bridging sulfur atoms and three atoms from the ligand (hydroxyl, alpha-, beta-carboxylates, sulfide or amine). The coordination mode of homocitrate ligand in K5(NH4)[Mo2O2S2(C7H5O7)2].3H2O.CH3OH (1) has been proposed in a tridentate fashion via its hydroxyl and a pair of carboxylate groups (alpha-, beta-carboxylates). The electrochemical properties of these complexes have been discussed.

Heptaaquatetra-mu3-hydroxy-hexa-mu2-L-leucine-(L-leucine)tetraytterbium(III) tetrachlorozinc(II) trichlorohydroxyzinc(II) tetrachloride octahydrate.

The title bimetallic compound, [Yb4(mu3-OH)4(C6H13NO2)7(H2O)7][ZnCl4][ZnCl3(OH)]Cl4.8H2O, was synthesized at near physiological pH (6.0). The compound exhibits some novel structural features, including an asymmetric [Yb4(mu3-OH)4(L-leucine)7(H2O)7]8+ complex cation in which four OH groups act as bridging ligands, linking four Yb3+ cations into a Yb4O4 structural unit. Each pair of adjacent Yb3+ ions is further bridged by one carboxy group from a leucine ligand. Water molecules and a monodentate leucine ligand also coordinate to Yb3+ ions, completing their eight-coordinate square-antiprismatic coordination. The Yb4(mu3-OH)4(L-leucine)7(H2O)7]8+ cation, the [ZnCl4]2-, [ZnCl3OH]2- and Cl- anions, and the lattice water molecules are linked via hydrogen bonds.