Ditantalum dinitrogen complex: reaction of H2 molecule with "end-on-bridged" [Ta(IV)]2(μ-η(1):η(1)-N2) and Bis(μ-nitrido) [Ta(V)]2(μ-N)2 complexes

To elucidate (i) the physicochemical properties of the {(η(5)-C(5)Me(5))[Ta(IV)](i-Pr)C(Me)N(i-Pr)}(2)(μ-η(1):η(1)-N(2)), I, [Ta(IV)](2)(μ-η(1):η(1)-N(2)), and {(η(5)-C(5)Me(5))[Ta(V)](i-Pr)C(Me)N(i-Pr)}(2)(μ-N)(2), II, [Ta(V)](2)(μ-N)(2), complexes; (ii) the mechanism of the I → II isomerization; and (iii) the reaction mechanism of these complexes with an H(2) molecule, we launched density functional (B3LYP) studies of model systems 1, 2, and 3 where the C(5)Me(5) and (i-Pr)C(Me)N(i-Pr) ligands of I (or II) were replaced by C(5)H(5) and HC(NCH(3))(2), respectively. These calculations show that the lower-lying electronic states of 1, [Ta(IV)](2)(μ-η(1):η(1)-N(2)), are nearly degenerate open-shell singlet and triplet states with two unpaired electrons located on the Ta centers. This finding is in reasonable agreement with experiments [J. Am Chem. Soc. 2007, 129, 9284-9285] showing easy accessibility of paramagnetic and diamagnetic states of I. The ground electronic state of the bis(μ-nitrido) complex 2, [Ta(V)](2)(μ-N)(2), is a closed-shell singlet state in agreement with the experimentally reported diamagnetic feature of II. The 1-to-2 rearrangement is a multistep and highly exothermic process. It occurs with a maximum of 28.7 kcal/mol free energy barrier required for the (μ-η(1):η(1)-N(2)) → (μ-η(2):η(2)-N(2)) transformation step. Reaction of 1 with H(2) leading to the 1,4-addition product 3 proceeds with a maximum of 24.2 kcal/mol free energy barrier associated by the (μ-η(1):η(1)-N(2)) → (μ-η(2):η(1)-N(2)) isomerization step. The overall reaction 1 + H(2) → 3 is exothermic by 20.0 kcal/mol. Thus, the addition of H(2) to 1 is kinetically and thermodynamically feasible and proceeds via the rate-determining (μ-η(1):η(1)-N(2)) → (μ-η(2):η(1)-N(2)) isomerization step. The bis(μ-nitrido) complex 2, [Ta(V)](2)(μ-N)(2), does not react with H(2) because of the large energy barrier (49.5 kcal/mol) and high endothermicity of the reaction. This conclusion is also in excellent agreement with the experimental observation [J. Am Chem. Soc. 2007, 129, 9284-9285].     

THE CRYSTAL STRUCTURE OF DI-μ-CHLORO-HEXACHLORO-BIS (ETHYL-CYANOFORMATE-N) DITITANIUM (IV)

Abstract

Crystals of the adduct titanium tetrachloride-ethylcyanoformate (1–1) are monoclinic a =9.06 Å, b =18.36 Å, c =13.83 Å, β =113°.2, space group C2/c, Z =8. The structure was solved by application of X-Ray diffraction techniques at room temperature. Atomic positions were refined by a full-matrix least-squares method to a final R of 0.049 using 829 non-zero independent reflections. This compound is dimeric with a double chlorine bridge between titanium atoms. Titanium is octahedrally coordinated to five chlorine atoms and to the nitrogen atom of the nitrile group and not to the oxygen atom of the carbonyl group. Thus in this complex the nitrogen atom is a better donor than the carbonyl oxygen.     

CRYSTAL STRUCTURE OF BIS(μ-SULFIDO)-BIS[OXO-DIETHYL-DITHIOCARBAMATO-MOLYBDENUM(V)]

<正> INTRODUCTION. Reaction of MoCl_3·3H_2O with dithio-carbamate to synthesize dinuclear or trinuclear molybdenum complexes is an interesting topic. We have obtained sulfido-bridged molybdenum(V) complex Mo_2(μ-S)_2O_2(S_2CNEt_2)_2 by reacting MoCl_3·3H_2O with NadtcEt_2 in MeOH solvent. The molecular structure of the title compound was characterized by, X-ray structure determination. We report the result of the structure determination in this paper.     

STRUCTURE OF A Fe-S CLUSTER COMPLEX [{(μ-PhCH_2S)Fe_2(CO)_6}_2(μ4-S)]

<正> [{(μ-PhCH2S)Fe2(CO)6}2(u4-S)], Mr = 837.95, triclinic, Pl,a=13.701(3),b=16.542(5), c=17.030(5)A,α=107.69(2),β=90.15(2),γ= 114.49(2)°,V=3309.3A3, Z=4, Dx=1.68 g/cm3,MoKa,λ=0.71069A μ=20.2 cm-1,F(000)=2008, room temperature, final R=0.035 for 4960 independent reflections. The molecule possesses approximate C2 symmetry with the pseudo-twofold axis passing through the unique sulfur atom u4-S(2) and the midpoint of the other two u2-sulfur atoms S(1) and S(3). The unique u4-sulfur atom has a tetrahedral geometry and donates its six valence electrons to the four iron atoms. The average Fe-(μ4-S) distance of 2.247 A is slightly shorter than the average Fe-(μ2-S) distance of 2.265A.     

Syntheses,crystal structures,and luminescence of coordination polymers [Cu(μ-Br)(μ-phpzm)] n , [{Cu(μ-SCN)}2(μ-phpzm)] n,and [(phpzm)Cu(μ-CN)] n (phpzm = bis(4-phenylpyrazol-1-yl)methane)

Solvothermal reactions of CuX (X?=?Br, SCN, CN) with bis(4-phenyl-pyrazol-1-yl)methane (phpzm) gave two 2-D coordination polymers, [Cu(μ-Br)(μ-phpzm)] _n (1) and [{Cu(μ-SCN)}₂(μ-phpzm)] _n (2), and a 1-D coordination polymer, [(phpzm)Cu(μ-CN)] _n (3). Compounds 1–3 were characterized by elemental analysis, IR spectra, and X-ray crystallography. Compounds 1 and 2 have 2-D networks in which split-stair [Cu(μ-Br)] _n chains (1) or staircase-like [Cu(μ-SCN)] _n double chains (2) are linked by μ-phpzm bridges. Compound 3 consists of a zigzag chain formed by linking [Cu(phpzm)] fragments via cyanide bridges. Luminescence properties of 1–3 along with phpzm in the solid state at ambient temperature were also investigated.     

CYCLOADDITION REACTION OF THE AZIDO-BRIDGED CYCLOMETALLATED COMPLEX [Pd(dmba)N3]2 WITH CS2. CRYSTAL AND MOLECULAR STRUCTURE OF DI(μ, N,S-l,2,3,4-THIATRIAZOLE-5-THIOLATE)BIS[(N,N-DIMETHYLBENZYL-AMINE-C2,N)PALLADIUM(II)]

Abstract

The 1,3-dipolar cycloaddition of carbon disulfide to the coordinated azide in the cyclometal-lated compound [Pd(dmba)(N₃)]₂ (1), dmba = N,N-dimethylbenzylamine, was investigated. The compound obtained di(μ, N, S-l,2,3,4-thiatriazole-5-thiolate)-bis[(N,N-dimethylbenzylamine-C², N)palladium(II)] (2), was characterized by IR spectroscopy and X-ray diffraction. Complex (2) is dimeric with the two [Pd(N,N-dimethylbenzylamine)] moieties being connected by the two vicinal bridging N, S-l,2,3,4-thiatriazole-5-thiolate anions in a square-planar coordination for the palladium atoms.     

THE POLYMERIC COPPER(II) COMPLEX 1, 10-PHENANTHROLINE -N,N '-(μ-ISONICOTINATO-N,O) MONOAQUACOPPER(II) NITRATE DIHYDRATE

Abstract

The title complex has been prepared and its structure determined by X-ray diffraction. The complex crystallizes in space group C2/c with a = 26.892(5), b = 10.479(4), c = 14.179(2) Å, β = 98.59(2)°. Isonicotinate anions bridge adjacent Cu(II) atoms through the pyridine N atom and the carboxyl O atom to form zigzag polymeric chains along the b axis. The carboxyl group of the isonicotinate anion coordinates to the Cu(II) atom as a unidentate. Based on the molecular structure the infrared spectrum is discussed.     

THE SYNTHESIS AND STRUCTURE OF Mo_3(μ_3-O)(μ-S)_3(μ-O_2CC_6H_5)_2(dtp)_2(Py)

<正> The title compound was prepared by reaction of Mo3(μ3-O) (μ-S)3-(dtp)4 (H2O) with C6H5COONa and pyridine. C27 H35 Mo3NO9P2S7, Mr = 1091.76, monoclinic, space group P21/c, a = 15. 057(5), b = 13. 052(5), c = 21. 662(6)(?), β=105.97(2)°, V = 4093(2) (?)3, Z = 4, Dc= 1. 77gcm-3, F(000) = 2176, μ(MoKα)=13.50cm-1, final R =0. 068 for 2835 observations. The molecular configuration is new and of approximate C, symmetry, and there are two C6H5COO bridging groups in the structure. The three Mo atoms form an isosceles triangle with three sides of 2. 567(3), 2. 576(3), and 2. 649(3)(?), where the two Mo-Mo bonds bridged by C6H5COO group are much shorter than that without. Something about the reactivity of Mo clusters is discussed.     

CRYSTAL STRUCTURE OF (μ-PYRAZINE)-BIS[DIAQUA(IMINODIACETATO) COPPBR(Ⅱ)] DIHYDRATE

<正> PRELIMINARY INFORMATION. Recently multinuclear complexes with bridging ligand have been found possibly to possess special catalytical and special electric properties. Therefore more attention has been paid to such complexes. This study is a part of systimatic investigations on structures and properties of the kind of complexes, which have been carred out previously.     

STUDIES ON THE TOTAL SYNTHESES OF MAYTANSINOIDS (Ⅲ)——SYNTHESIS OF C_5-N FRAGMENT

The synthesis of an important intermediate, C_5-N fragment of maytansine, is described in this paper. This fragment possesses aromatic moiety, two conjugated trans-double bonds and three asymmetrical carbons, C_6, C_7, C_(10), of maytansine.     

Synthesis, crystal and molecular structures of an isomorphic N, S-bridged [Cu2(μ2-I)2(PPh3)2(μ2-N, S-pymSH)] dimer and S-bonded [CuX(η1-S-pymSH)(PPh3)2] monomers (X = Cl, Br)

Abstract  Monoclinic crystals of [Cu₂(μ-I)₂(PPh₃)₂(μ-N, S-pymSH)] · CH₃CN) (1), were obtained by equimolar reaction of copper(I) iodide with pyrimidine-2-thione (pymSH), followed by the addition of triphenylphosphine (PPh₃) in acetonitrile. Crystal data for 1: space group P2₁, Z = 2, a = 9.896, b = 18.378, c = 11.703 ?, β = 101.73°. It has an iodo-bridged Cu(μ-I)₂Cu core and the pyrimdine-2-thione binds to both Cu centers via N, S-bridging across the Cu(μ-I)₂Cu core. This N, S-bridging, a rare coordination mode for pyrimidine-2-thione, leads to a short Cu···Cu separation of 2.675(2) ? (sum of van der Waals radius of Cu atoms, 2.80 ?). The geometry around each Cu center is distorted tetrahedral with angles varying in the range, ca. 102–119°. Copper(I) chloride and bromide also yielded monoclinic crystals of S-bonded tetrahedral monomers, [CuBr(pymSH)(PPh₃)₂] 2 and [CuCl(pymSH)(PPh₃)₂] 3. Crystal data for 2: space group P2₁/n, Z = 8, a = 12.825, b = 43.122, c = 13.396 ?, β = 90.79°. Crystal data for 3: space group P2₁/c, Z = 4, a = 14.340, b = 10.111, c = 24.200 ?, β = 94.36°. Compound 2 has two crystallographically independent molecules in crystal lattice. The ³¹P NMR spectrum of 1 showed two signals for PPh₃ ligands bonded to two Cu centers with different coordination cores: CuI₂PN and CuI₂PS. Both 2 and 3 showed one signal each for PPh₃ in their ³¹P NMR spectra. Graphical abstract  Reaction of copper(I) iodide with pyrimidine-2-thione and triphenylphosphine formed monoclinic crystals of dimer 1 with unusual N, S-bridging across Cu(μ₂-I)₂Cu core.      

SYNTHESIS AND STRUCTURE OF DIAQUO-μ-TRIETHYLENETE-TRA AMINOHEX A ACETATODI ANTIMONY ( Ⅲ) , C(H_2O)Sb(ttha)Sb-(H_2O)]

<正> C_18H_28N_4O_14Sb_2, MT = 767. 94, monoclinic, space group P2_1/c, a = 13. 847(2),b=6.866(2),c=13. 846(2) A,β=116. 46(1)°,V=1180. 3A3,Z=2,Dc = 2. 161g/cm3, F(000) = 756,μ(MoKa) = 23. 83cm-1. R and Rw were 0.054 and 0. 060, respectively, for 1357 observed reflections at room temperature. Each binuclear complexes arranged so that the centre of the carbon-carbon bond in the ethylenediamine group lies on a crystallographic centre of inversion. The ethylenediamine group forms a bridge between the two halves of the title molecule. Each antimony atom is ψ-heptacoordi-nated by a lone electron pair,one O atom from a water molecucle,one O atom from an ac-etato group and two amino N atoms at the equatorial plane as well as two O atoms from the acetato groups at the axial positions forming a pentagonal bipyramid.     

PHOTOPHYSICS STUDIES OF ORCANIC COMPOUNDS (Ⅻ)——THE INVESTIGATION OF THE FLUORESCENCE SPECTRA OF N-SALICYLIDENE-p-(N,N-DIMETHYLAMINO)ANILINE

The fluorescence spectra of N--salicylidene-p-(N,N--dimethylamino)aniline have beeninvestigated in various solvents. Three kinds of fluorescence have been found in the solutionsof various concentrations. They are the excited intermediate (EI) which is formed when theproton transfer has occurred but essentially retains the geometry of the enol tautomer, theexciplex (EX) which consists of a ground monomer and an excited state intermediate and theexcited dimer (ED) which is caused by ground state aggregate. The fluorescence lifetimesof the fluorophores have been measured in tetrahydrofuran (THF). Luminescent mechanismhas been discussed based on the fluorescence spectra and the kinetic data of the compound.     

STRUCTURAL STUDIES OF THE COPPER(II) ACETATE COMPLEXES Cu(o2CCH3)2(pyridine)3 AND Cu6(μ-O2CCH3)4(μ4-O2CCH3)2(μ-OCMe3)6

Abstract

[Cu(O₂CCH₃)₂]₂, 1, reacts with pyridine to form violet-blue Cu(O₂CCH₃)₂(pyridine)₃, 2, in > 90% yield. 2 crystallizes from pyridine with a distorted square-pyramidal geometry around copper with the monodentate acetate ligands located diagonally in the basal positions. 1 reacts with Bi(OCMe₃)₃ in THF to form blue Cu₆(μ-O₂CCH₃)₄(μ₄-O₂CCH₃)₂(μ-OCMe₃)₆, 3. 3 crystallizes from THF/hexanes with a hexagon of copper atoms linked by six doubly-bridging tert-butoxide ligands, four doubly-bridging bidentate acetates, and two quadruply-bridging bidentate acetate ligands.     

SYNTHESIS AND STRUCTURE OF A PENTAMETHYLCYCLOPENTADIENYL THULIUMCHLORIDE COMPLEX, [(C5ME5)2Tm(μ3-CL)2K(THF)]N

Abstract

The first structural data on a pentamethylcyclopentadienyl complex ofthulium, [(C₅Me₅)₂Tm(μ₃-C1)₂K(THF)]_n,1, are reported. TmCl₃ reacts with 2 equivalents ofKC₅Me₅ in THF to form 1 in <80% yield. 1 crystallizes from THF/hexanes in thespace group Cc with a = 11.1491(13) Å, b= 28.107(2) Å, c = 8.5921(8) Å, β= 102.485(8)°, V = 2628.8(4) ų, and D_calcd = 1.570 Mg/m³ for Z= 4. Least-squares refinement of the model based on 3114reflections (F² > 3.0 [sgrave] (F²))converged to a final R_F = 1.9%. Thepolymeric structure of 1 is generated by triply bridgingchlorides, each of which is connected to one(C₅Me₅)₂Tm bentmetallocene unit and two K(THF) moieties in a T-shaped geometryaround the chloride.     

THE PREPARATION,STRUCTURE AND PROPERTES OF Sr_(0.5)Ca(0.5)CuO_2

Sr_(0.5)Ca_(0.5)CuO_2 has been synthesized by the solid state reaction.Thecompound crystallizes in an orthorhombic unit cell,space group D_(2h)~(17)-Cmcmwith a=3.444 ,b=16.11 ,c=3.868 .It decomposes shove 1038℃.Sr_(0.5)Ca_(0.5)CuO_2 is s black p-type semiconductor with resistivity 53Ω.cmat room tempersture.     

Tetranuclear azido-bridged copper(II) complex [Cu4(μ-salpn)2(μ1,1-N3)2(N3)2(H2O)2]: Synthesis,characterization and crystal structure

The reaction of salpnH₂ Schiff-base ligand (salpnH₂ = N,N′-bis(salicylidene)-1,3-propylenediamine) with Cu(NO₃)₂·3H₂O and a large excess of NaN₃ (1:2:8 molar ration), lead to the formation of [Cu₄(μ-salpn)₂(μ_1,1-N₃)₂(N₃)₂(H₂O)₂] (1), which has been successfully obtained and characterized by elemental analyses, IR spectroscopy and single-crystal X-ray diffraction. The strong absorption band at about 2000–2100 cm^?1 and at 1597 cm^?1 regions of the IR spectrum of 1 clearly proves the presence of the both end-on (EO) bridging and terminal azido ions and CN (azomethine) groups, respectively. Single-crystal X-ray analyses revealed that the copper atoms are bridged alternately by end-to-on (EO) azido and phenoxo-salpn ligands in the prepared tetranuclear copper(II) complex [Cu₄(μ-salpn)₂(μ_1,1-N₃)₂(N₃)₂(H₂O)₂] (1).     

CRYSTAL AND MOLECULAR STRUCTURE OF (μ-SPh) (μ-SCH2CH2CN)Fe_2 (CO)_6

<正> The crystal and molecular structure of (μ-SPh)(μ-SCH2CH2CN)Fe2-(CO)5 has been determined by X-ray diffraction method. The crystals of this complex are triclinic, space group P1,with a=ll.175(1), b=ll.877(2), c= 15.640(2)1,α=106.20(1),β=103.15(1),γ=98.46(1)°; Z=4; Dc=1.67g/cm3. The final structure refinement converged with unweighted and weighted R factors of 0.028 and 0.034 for 2853 observed unique reflections.     

THE STRUCTURE OF TRIS(PYRIDINUM)(μ_3-SULFIDO)-TRIS(μ-DISULFIDO)-HEPTA-CHLORO-TRIMOLYBDENUM, (PyH)_3[Mo_3(μ_3-S)(μ-S_2)_3Cl_7]·1/2H_2O

<正> M=1101.86, cubic, Pa3, a=19.605(2), V=7533(3)A3, Z=8, Dc=1.943 g.cm-3. Final R=0.041 for 1120 reflections. The cluster anion is a mono(μ3-S) capped trinuclear species with each Mo atom having a distorted pentagonal bipyramidal coordination. A striking feature of this anion, which sharply differs from [Mo3S13] 2-,2 is the existence of a Cl atom connecting three S atoms by covalent bond to some extent.     

Crystal Structure and Inhibitory Activity against Xanthine Oxidase of Bis(μ2-chloro)-chloro-(μ-N,N'-(2-pyridylmethylene)Furanmethanoamine Copper(Ⅱ)Complex

A chloro-bridged dinuclear copper(Ⅱ) complex with ligand 2-pyridylme-thylene-furfurylamine has been synthesized and characterized by single-crystal X-ray diffraction,and its inhibitory activity on xanthine oxidase(XO)Was also evaluated.It crystallizes in the triclinic system,space group P-1 with a=8.0441(16),b=8.5663(17),c=10.060(2)(A),α=77.52(3),β=72.04(3),γ=70.12(3)°,V=615.3(2)(A)3,Z=1,Dc=1.731 g/cm3,F(000)=322,the final R=0.0401 and wR=0.0934 for 1971 observed reflections with Ⅰ＞2σ(Ⅰ).X-ray analysis reveals that the Cu(Ⅱ)cation is five-coordinated by two N atoms of Schiff base and three C1 anions.The C-H…Cl intermolecular and intramolecular hydrogen bonds connect the molecules to form a three-dimensional network.Tilis copper(Ⅱ) complex shows more potent inhibitory activity against XO with Ⅰ C50=3.48/μM than the standard inhibitor allopurinol.