Pan-Wen Shen

Synthesis, Crystal Structure and Properties of Novel Zinc(II) and Cobalt(II) Chain Complexes with 3,5-dimethylpyrazole and Thiocyanate

This paper presents the synthesis, crystal structure and properties of new zinc(II) and cobalt(II) 1-D chain complexes with 3,5-dimethylpyrazole and thiocyanate, [M(pz*)2(NCS)2]·H2O (M=Zn, Co;pz*=3,5-dimethylpyrazole). The structures of both complexes were determined by X-ray diffraction methods and showed very similar crystallographic character. The M(II) ion in each complex is coordinated to two pyrazole nitrogen atoms and two nitrogen atoms of NCS- to form a distorted tetrahedron. In the cell of each complex are four complex molecules and four H2O molecules. Adjacent complex molecules are connected by hydrogen bonds to form 1-D chain. Each sulfur atom in the complex is connected by a weak coordination bond with an M(II) ion of an adjacent chain to form a sawtooth-type double 1-D chain structure. The bond distances Zn-S and Co-S are 3.919 Å and 3.853 Å, respectively.

New half-sandwich nickel(II) complex with mono-hydrotris- (3,5-dimethylpyrazolyl)borate ligand and nitrite

Abstract This paper presents the syntheses, crystal structure and properties of a new half-sandwich mononuclear nickel(II) complex containing a single hydrotris(3,5-dimethylpyrazolyl)borate (Tp*) ligand and nitrito and methanol co-ligands, [Tp*NiII(η2-O2N)(CH3OH)]. The complex crystallizes in the triclinic system, space group P 1 (No. 2), a=10.0669(11), b=10.1132(11), c=11.8420(12) A, α=76.895(2), β=73.234(2), γ=62.470(2)°, Z=2, R1=0.0458, wR2=0.1187. The Ni(II) ion in the complex is coordinated to three pyrazolyl nitrogen atoms, two oxygen atoms of NO2− and one oxygen atom of CH3OH to form a distorted octahedron. The NO2− was coordinated in an asymmetric nitrito-O,O′-bidentate coordination mode with an O(1)–Ni–O(2) angle of 57.71(11)° and Ni–O bond lengths of 2.1882 and 2.1222 A.

Synthesis, crystal structures and magnetic properties of transition metal–azide complexes coordinated with pyridyl nitronyl nitroxides

Abstract Two novel complexes Co(N3)2(PNN)4 (I) and Mn(N3)2(PNN)2(CH3OH)(C2H5OH) (II) (PNN=2-(p-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3–oxide) were synthesized and characterized by infrared spectra, elemental analyses and UV–Vis techniques. The crystal structures of both complexes have been determined by X-ray diffraction analysis. Complex I is a neutral five-spin system and adopts a centrosymmetric tetragonally compressed octahedral coordination geometry in which Co(II) ion is coordinated to four radicals through the nitrogen atoms of the pyridine rings and two azide anions occupying the axial positions. Complex II is a neutral three-spin system in which Mn(II) ion is bound to two azide anions, two alcohol molecules and two radicals through the nitrogen atom of pyridine rings, and shows one-dimensional chain structure via hydrogen bonds (dO⋯N=2.78 A). The magnetic properties for complexes I and II have been investigated in the temperature range 2–300 K. A theoretical model has been developed for complex I and the magnetic behaviors for both complexes have been discussed in detail.

1D zigzag coordination polymer [Cu(tacn)(4,4′-bipy)]n·(ClO4)2n (tacn=1,4,7-triazacyclononane): structure, spectroscopic, and magnetic properties

Abstract A new one-dimensional coordination polymer, [Cu(tacn)(4,4′-bipy)]n ·(ClO4)2n (tacn = 1,4,7-triazacyclononane, 4,4′-bipy = 4,4′-bipyridine), has been synthesized and characterized by X-ray crystallography, elemental analysis, IR, electronic spectra, ESR and variable-temperature magnetic susceptibility (4–300 K). The Cu(II) ion is five-coordinated in a distorted square-pyramidal environment to three nitrogens of tacn and two nitrogens from two 4,4′-bipy ligands. Each 4,4′-bipy, in which two pyridine rings are slightly twisted, links two [Cu(tacn)]2+ units to form 1D zigzag chain. The magnetic behavior shows very weak interaction between metal ions.

SYNTHESIS AND SPECTROSCOPIC STUDIES OF MANGANESE PORPHYRIN-THIOLATE COMPLEXES

Abstract The synthesis and spectroscopic characterization of four manganese(III) porphyrin thiolates are reported. The investigated compounds are represented by (TPP)Mn(SR), where TPP is the dianion of tetraphenylporhyrin and R is C 6 H 5 , C 6 H 4 ( p -NO 2 ), Et 2 NCS and C 4 H 8 NCS. Each complex was characterized by UV-vis and 1 H NMR spectroscopy. The effects of axial ligands on the UV-vis spectra of synthesized manganese porphyrin complexes is discussed and proton isotropic shifts are shown to be predominantly contact in origin, reflecting extensive porphyrin-to-metal π bonding.

The comparison of structure and bond between [Ni(pzph)4(NCS)2] and [Ni(pzBut)4(NCS)2]

Two nickel(II) complexes with thiocyanate and different substituted pyrazole ligands, [Ni(pz R )4(SCN)2 ]( R¼ ph for (1) and n-But for (2), pz R ¼ 3-substituted pyrazole), have been synthesized and their crystal structures have been determined. The compound 1 crystallizes in the monoclinic system, space group P21/n, a ¼ 8:591ð5Þ A; b ¼ 17:936ð10Þ A; c ¼ 12:861ð7Þ A; b ¼ 106:490ð10Þ8; Z ¼ 2; R1 ¼ 0:0665; wR2 ¼ 0:1375: The compound 2 crystallizes in the monoclinic system, space group P21/c, a ¼ 12:805ð3Þ A; b ¼ 22:718ð5Þ A; c ¼ 13:396ð3Þ A; b ¼ 94:480ð5Þ8; Z ¼ 4; R1 ¼ 0:0729; wR2 ¼ 0:1665: The nickel(II) ion in each complex is coordinated by four pyrazole nitrogen atoms and two nitrogen atoms of NCS 2 to form a distorted octahedron. The two nitrogen atoms of NCS 2 are located at axial positions and the four nitrogen atoms of pyrazoles are located at equatorial positions. The average Ni – N(pz R ) and Ni– N(NCS) bond lengths are observed to be 2.111 and 2.068 A u for 1, 2.095 and 2.098 A u for 2, respectively. In 1, the intermolecular hydrogen bonds form quasi 1D structure. The intramolecular hydrogen bonds are found in 2. The spectroscopic and bond properties have also been discussed. q 2002 Elsevier Science B.V. All rights reserved.

The first example of half-sandwich cobalt(III) complex with hydrotris(pyrazolyl)borate ligand

Abstract This paper presents the synthesis, crystal structure and spectroscopic properties of a novel half-sandwich mononuclear cobalt(III) complex with hydrotris(3,5-dimethylpyrazolyl)borate ligand and thiocyanate [Tp*Co(Hpz*)(NCS)2]·H2O·CH3OH (Tp*: hydrotris(3,5-dimethyl- pyrazolyl)borate, Hpz*: 3,5-dimethylpyrazole). The structure was determined by X-ray diffraction. The complex crystallizes in the monoclinic system, space group Cc, a=18.591(6) A, b=10.536(3) A, c=17.568(5) A, β=11.284(5)°, Z=4, R1=0.0501, wR2=0.1179. The cobalt(III) ion in the complex is six-coordinated with nitrogen atoms, three from Tp*, two from pyrazole and two from two thiocyanates, to form octahedral environment. The hydrogen atoms of O(2) of water molecule are connected by hydrogen bonds with S atoms of two adjacent complex molecules to form 1-D chains. The hydrogen atom of N(8) of complex molecule is connected by hydrogen bond with methanol. The spectroscopic results are consistent with the crystallographic study.

Experimental and theoretical studies of the dehydration kinetics of two inhibitor-containing half-sandwich cobalt(II) complexes

Abstract Two inhibitor-containing half-sandwich cobalt(II) complexes [TpMe]CoX ([TpMe] = hydrotris(3,5-dimethylpyrazolyl)borate; X−: N3− (1), NCS− (2)) have been synthesized and characterized. The structure of 2 was determined by X-ray crystallographic analysis. The dehydration kinetic measurements of HCO3− catalyzed by the cobalt(II) complexes are performed by the stopped-flow techniques at pH

Kinetics and mechanism of the bicarbonate dehydration of the half-sandwich zinc(II) complexes [TpPh]ZnX ([TpPh] = hydrotris(3-phenylpyrazolyl)borate; X− = OH−, N3−, NCS−)

Abstract The preparation and characterization of the half-sandwich zinc complexes [Tp Ph ]ZnX ([Tp Ph ] = hydrotris(3-phenylpyrazolyl)borate; X − = OH − ( 1 ), N 3 − ( 2 ), NCS − ( 3 )) have been described. The bicarbonate dehydration kinetic measurements are performed by the stopped-flow techniques at pH k obs d varies linearly with the total Zn(II) concentration, and the catalytic activity of the model complexes decreases in the order 1 > 2 > 3 . The catalytic activity decreases with increasing pH, which indicates that the aqua model complex must be the reactive catalytic species in the catalyzed dehydration reaction and the rate-determining step is the substitution of the labile water molecule by HCO 3 − . The k obs d values increase with increasing reaction temperature, and the apparent activation energies of the model complexes with small inorganic ions are remarkably higher, this being the origin of inhibition. The large negative entropy of activation also indicates an associative mode of activation in the rate-determining step. The inhibition ability of NCS − is strong than that of N 3 − , which can be rationalized by the decrease in effective atomic charges of the Zn(II) ions as revealed by the theoretical calculations.

Synthesis, properties, structure and bioactivity in vitro of mononuclear complexes of manganese and nickel with hydroxyethyltribenzimidazolylmethyl ethylene diamine

Abstract Six novel mononuclear complexes, MnCl2L·H2O, Mn(SCN)2L·2H2O, Mn(ClO2)2L·2H2O, NiCl2L·2H2O, Ni(SCN)2L·H2O, Ni(ClO4)2L (L  N-hydroxyethyl-N,N′,N′-tribenzimidazolylmethyl ethylene diamine), have been synthesized and characterized. The UV-visible spectra of nickel complexes reveal that L is a weak field ligand. The ESR spectra indicate the asymmetric electronic environment of the manganese ion in its complex. The crystal and molecular structures of Ni(SCN)2L·H2O were determined by X-ray diffraction analysis. The nickel ions have distorted octahedral symmetry. The preliminary results of bioassay of the complexes showed that monomanganeses have antitumour activities in vitro.