钛配合物Cp2TiL,Cp2Ti2Cl2(μ-O)和Cp4Ti4Cl4(μ-O)4的合成与晶体结构研究(Cp=η5-C5H5,L=2,6-吡啶二羧酸盐)

利用溶剂热的方法将Cp2TiCl2(Cp=η5-C5H5)与2,6-吡啶二羧酸钠(L)反应,不同的反应时间得到了2个具有不同晶体空间群的化合物Cp2TiL(1a和1b),而在常温或低温下,Cp2TiCl2或CpTiCl3同羧酸盐或亚胺反应却得到了双核或四核氧桥联的钛化合物。     

DFT studies of the methyl exchange reaction between Cp2M-CH3 or Cp*2M-CH3 (Cp = C5H5, Cp* = C5Me5, M = Y, Sc, Ln) and CH4. Does M ionic radius control the reaction?

The activation energies for the methyl exchange reactions between Cp2M-CH3 and H-CH3 have been calculated for M = Sc, Y and representative metals of the lanthanide family (La, Ce, Sm, Ho, Yb and Lu) with DFT(B3PW91) calculations with large-core pseudopotentials for M. The sigma-bond metathesis reactions are calculated to have lower activation energies for early lanthanides than for late lanthanides and any of group 3 metals. The relative activation barriers are analyzed using the NBO charge distributions in the reactant and in the transition states. It is shown that the methane needs to be polarized in the transition state as H((+delta))-CH3((-delta)) by the reactant, because this sigma-bond metathesis is best viewed as heterolytic cleavage of methane, leading to a proton transfer between two methyl groups in the field of an electropositive M metal. Early lanthanides, which are involved in strongly ionic metal-ligands bonds are thus associated with the lowest activation energies. The ionic radius and the steric effects influence the relative rates of reaction for the complexes of Sc, Y and Lu. In agreement with earlier works of Sherer et al., the experimental reactivity trends found by Tilley are reproduced best with Cp*2M-CH3 (Cp* = C5Me5) rather than Cp2M-CH3 (Cp = C5H5) because the steric bulk of C5Me5 deactivates most the complex where the metal has the smallest ionic radius (Sc). While the steric effects and the influence of the metal ionic radius cannot be neglected, these factors are not the only ones involved in determining the activation barriers of the sigma-bond metathesis reaction.     

C-H activation of arenes and heteroarenes by early transition metallaborane, [(Cp*Ta)2B5H11] (Cp* = η5-C5Me5)

C-H activation of arenes and heteroarenes has been achieved by a hydrogen rich tantalaborane cluster [(Cp*Ta)(2)B(5)H(11)] that leads to the formation of C-H functionalized products. Furthermore, we examined the reaction of substituted thiophene and pyrrole derivatives with tantalaborane which provided a convenient and efficient route to regio-defined C-H functionalized heteroarenes.     

Synthesis and structures of new heterometallic clusters [Fe2(MCp x )(CO)6(μ3-S)2] (M = Rh, Ir; Cp x = Cp*, C5H3But 2)

The reaction of the [Fe₂(CO)₆(μ-S)₂]^2? anion (prepared in situ by reduction of [Fe₂(CO)₆(μ-S₂)] with Na/K alloy) with [Cp″RhCl₂]₂ (Cp″ = η⁵-(1,3-Bu^t ₂)C₅H₃) and [Cp*Ir(CH₃CN)₃](CF₃SO₃)₂ (Cp^* is pentamethylcyclopentadienide) yielded new heterometallic clusters [Fe₂(MCp ^x )(CO)₆(μ₃-S)₂]. The core of the resulting clusters can be described as the distorted [Fe₂S₂M] square pyramid with the M atom in the apical position. The structures of the clusters were established by X-ray diffraction.     

The photo-induced decarbonylation of Cp′M(NO)(CO)2 (M = Cr,Mo, W) with diorgano dichalcogenides (R2E2; E = S,Se; R = Me,Ph)

The photo-induced decarbonylation of CpCr(NO)(CO)₂ (1a) in MeCN solution in the presence of R₂E₂ (E = S, Se; R = Me, Ph) leads to the formation of chalcogenolato-bridged binuclear complexes Cp₂Cr₂(NO)₂(-ER)₂ [E = S; R = Me (2a), Ph (3a); E = Se, R = Me (4a), Ph (5a)] while reactions between CpM(NO)(CO)₂ [M = Mo (1b), W (1c)] and Ph₂E₂ (E = S, Se) result in mononuclear complexes CpM(NO)(EPh)₂ [M = Mo; E = S (9b), Se (10b); M = W, E = S (11c), Se (12c)]. The corresponding reactions of (1b) with Me₂E₂ (E = S, Se) yielded both mono and binuclear complexes: CpMo(NO)(SeMe)₂ (8b), Cp₂Mo₂(NO)₂(-EMe)₂ [E = S (6b), Se (7b)]. The new complexes have been characterized by i.r., ¹H-, ¹³C-n.m.r. spectra and by electron-impact mass spectrometry.     

Synthesis and structures of the six-coordinate donor-acceptor complexes R3(C6H4O2)Sb…L (R=Ph, L=OSMe2 or ONC5H5; R=Me, L=ONC5H5 or NC5H5) and R3(C2H4O2)Sb…L (R=Ph, L=ONC5H5; R=Cl or C6F5, L=OPPh3)

One-pot oxidation of R₃Sb (R=Ph, Me, Cl, or C₆F₅) withtert-butyl hydroperoxide in the presence of 1,2-diols and monodentate donor compounds was studied. The structures of the resulting neutral organic donor-acceptor Sb^V complexes, Ph₃(C₆H₄O₂)Sb…OSMe₂, Ph₃(C₆H₄O₂)Sb…ONC₅H₅, Me₃(C₆H₄O₂)Sb…ONC₅H₅, Me₃(C₆H₄O₂)Sb…NC₅H₅, Ph₃(C₂H₄O₂)Sb…ONC₅H₅, and Cl(C₆F₅)₂(C₂H₄O₂)Sb…OPPh₃, were established by X-ray diffraction analysis. In these complexes, the coordination environment about the Sb atoms is a distorted octahedron. The Sb?O(N) distances and the Sb?O?E angles (E=S, N, or P) vary over wide ranges.     

Synthesis, NMR and quantum chemical studies of the [Cp3Rh3Se2]2+ clusters (Cp = η5-C5Me5, η5-C5Me4Et, η5-C5H3 t Bu2)

Reactions of [CpRhCl₂]₂ (Cp = η⁵-C₅Me₅ (Cp*), η⁵-C₅Me₄Et (Cp′), η⁵-C₅H₃ ^t Bu₂(Cp″)) with in situ generated H₂Se give triangular [Cp₃Rh₃Se₂]²⁺ clusters. These clusters were isolated as PF₆ salts and characterized with ESI-MS, ⁷⁷Se, ¹H NMR and DFT calculations. [Cp₃Rh₃Se₂] undergoes two reversible two-electron reduction steps. Quantum-chemical calculations reveal non-trivial bonding situation in the cluster core and changes in the hapticity of the Cp* ligand upon reduction. Crystal structure of [Cp ₃ ^* Rh₃Se₂][Re₂(μ-Cl)₃(CO)₆]Cl · 3.3H₂O has been determined.     

Synthesis and Structure of Tetraphenylantimony Oximates Ph4SbON=CRR′ (CRR′ = C6H9−C6H9-2 and R = Ph,R′ = C(O)Ph)

The reaction of pentaphenylantimony and the oxime HON=CRR taken in 1 : 1 molar ratio in toluene gave tetraphenylantimony oximates Ph₄SbON=CRR (CRR = C₆H₉–C₆H₉-2 (I) and R = Ph, R = C(O)Ph (II)). According to X-ray diffraction data, the Sb atoms in I and II have a distorted trigonal-bipyramidal coordination with oximate ligands in the axial positions. The C_axSbO angles are 177.6(1)° in I and 176.58(6)° in II. The Sb–C bond lengths lie in the ranges of 2.120(4)–2.203(4) Å for I and 2.122(2)–2.181(2) Å for II. The Sb–O bond lengths are 2.120(2) Å (I) and 2.166(1) Å (II). The lengths of the intramolecular Sb···N contacts are 2.806(3) and 2.918(2) Å in I and II, respectively.     

Synthesis,structure and photoluminescent properties of a new coordination polymer [Cd2(pzdc)2(4,4′-bpy)(H2O)2] n (H2pzdc = pyrazine-2,3-dicarboxylic acid, 4,4′-bpy = 4,4′-bipyridine)

A new 2D coordination polymer, [Cd₂(pzdc)₂(4,4′-bpy)(H₂O)₂] _n (1) (pzdc = pyrazine-2,3-dicarboxylic acid, 4,4′-bpy = 4,4′-bipyridine), has been hydrothermally synthesized and characterized by elemental analyses, IR spectra and single crystal X-ray diffraction. X-ray diffraction analysis reveals that 1 features an interesting 2D stair-like layer with linear [Cd₂(pzdc)₂(H₂O)₂] _n ribbons linked by 4,4′-bpy bridges. Furthermore, these layers are packed in an ABAB arrangement to give a 3D supramolecular network via hydrogen bonding and π–π packing interactions. Compound 1 displays strong fluorescent emission in the solid state at room temperature.     

Ethene polymerization with mixed-ring metallocene catalysts,Cp′Cp″MCl2, M = Ti and Zr

Mixed-ring metallocenes CpCpMCl₂ (Cp and Cp = cyclopentadienyl and its substituted derivatives; M = Ti and Zr) have been prepared by reacting CpMCl₃ with the Cp anion salt, in which the Cp–M bond is stronger than the Cp–M bond. Ethene has been polymerized with these complexes in the presence of methyl aluminoxane (MAO) as co-catalyst. The catalytic properties of titanocenes were influenced mainly by the steric effects of cyclopentadienyl ring substituents. Both steric and electronic effects of substituents influenced the catalytic properties of zirconocenes.     

Synthesis of 5′-amino- and 5′-azido-2′,5′-dideoxy nucleosides from thieno[2,3-d]pyrimidine-2,4(1H,3H)-dione

Summary Thieno[2,3-d]pyrimidine-2,4(1H,3H)-dione (4) was silylated and condensed with methyl 5-azido-2,5-dideoxy-3-O-(4-methylbenzoyl)-D-erythro-pentofuranoside (2) in the presence ofTMS triflate to afford the corresponding protected nucleoside6 and acyclic nucleoside7. Deprotection of6 with MeONa/MeOH at room temperature gave 1-(5-azido-2,5-dideoxy--D-erythro-pentofuranosyl)-thieno[2,3-d]pyrimidine-2,4(1H,3H)-dione (8) and the corresponding anomer9, whereas compound7 yielded 5-azido-2,5-dideoxy-1-(2,4-dioxo-1,2,3,4-tetrahydrothieno[2,3-d]pyrimidin-1-yl)-1-O-methyl-D-erythro-pentitol (10) under the same reaction conditions. 1-(5-Amino-2,5-dideoxy--D-erythro-pentofuranosyl)thieno[2,3-d]pyrimidine-2,4(1H,3H)-dione (11) was obtained on treating9 with Ph₃P in pyridine followed by hyrolysis with NH₄OH. The anomeric nucleosides14 and15 and the corresponding acyclic nucleoside16 were obtained when4 was trimethylsilylated and condensed with methyl 2-deoxy-3,5-di-O-(4-methylbenzoyl)-D-erythro-pentofuranoside (3) followed by deprotection with MeONa in MeOH. Compounds8 and9 were also obtained when the anomeric mixture14/15 was treated with a mixture of NaN₃, Ph₃P, and CBr₄ in dryDMF at room temperature.On leave from Chemistry Department, Faculty of Science, Tanta University, Tanta, Egypt     

Nature of M-Ga bonds in dihalogallyl complexes (η5-C5H5)(Me3P)2M(GaX2) (M = Fe, Ru, Os) and (η5-C5H5)(OC)2Fe(GaX2) (X = Cl, Br, I): a DFT study

Density functional theory (DFT) calculations have been performed on the terminal dihalogallyl complexes of iron, ruthenium, and osmium (η(5)-C(5)H(5))(Me(3)P)(2)M(GaX(2)) (M = Fe, Ru, Os; X = Cl, Br, I) and (η(5)-C(5)H(5))(OC)(2)Fe(GaX(2)) (X = Cl, Br, I) at the BP86/TZ2P/ZORA level of theory. On the basis of analyses suggested by Pauling, the M-Ga bonds in all of the dihalogallyl complexes are shorter than M-Ga single bonds; moreover, on going from X = Cl to X = I, the optimized M-Ga bond distances are found to increase. From the perspective of covalent bonding, however, π-symmetry contributions are, in all complexes, significantly smaller than the corresponding σ-bonding contribution, representing only 4-10% of the total orbital interaction. Thus, in these GaX(2) complexes, the gallyl ligand behaves predominantly as a σ donor, and the short M-Ga bond lengths can be attributed to high gallium s-orbital character in the M-Ga σ-bonding orbitals. The natural population analysis (NPA) charge distributions indicate that the group 8 metal atom carries a negative charge (from -1.38 to -1.62) and the gallium atom carries a significant positive charge in all cases (from +0.76 to +1.18). Moreover, the contributions of the electrostatic interaction terms (ΔE(elstat)) are significantly larger in all gallyl complexes than the covalent bonding term (ΔE(orb)); thus, the M-Ga bonds have predominantly ionic character (60-72%). The magnitude of the charge separation is greatest for dichlorogallyl complexes (compared to the corresponding GaBr(2) and GaI(2) systems), leading to a larger attractive ΔE(elstat) term and to M-Ga bonds that are stronger and marginally shorter than in the dibromo and diiodo analogues.     

Does covalency really increase across the 5f series? A comparison of molecular orbital, natural population, spin and electron density analyses of AnCp3 (An = Th-Cm; Cp = η(5)-C5H5)

The title compounds are studied with scalar relativistic, gradient-corrected (PBE) and hybrid (PBE0) density functional theory. The metal-Cp centroid distances shorten from ThCp(3) to NpCp(3), but lengthen again from PuCp(3) to CmCp(3). Examination of the valence molecular orbital structures reveals that the highest-lying Cp π(2,3)-based orbitals transform as 1e + 2e + 1a(1) + 1a(2). Above these levels come the predominantly metal-based 5f orbitals, which stabilise across the actinide series such that in CmCp(3) the 5f manifold is at more negative energy than the Cp π(2,3)-based levels. Mulliken population analysis shows metal d orbital participation in the e symmetry Cp π(2,3)-based orbitals. Metal 5f character is found in the 1a(1) and 1a(2) levels, and this contribution increases significantly from ThCp(3) to AmCp(3). This is in agreement with the metal spin densities, which are enhanced above their formal value in NpCp(3), PuCp(3) and especially AmCp(3) with both PBE and PBE0. However, atoms-in-molecules analysis of the electron densities indicates that the An-Cp bonding is very ionic, increasingly so as the actinide becomes heavier. It is concluded that the large metal orbital contributions to the Cp π(2,3)-based levels, and enhanced metal spin densities toward the middle of the actinide series arise from a coincidental energy match of metal and ligand orbitals, and do not reflect genuinely increased covalency (in the sense of appreciable overlap between metal and ligand levels and a build up of electron density in the region between the actinide and carbon nuclei).     

不对称型双核半夹心结构铁化合物Cp′2Fe2(CO)3Se2C2B10H10 (Cp′=η5-C5H4Me)的合成、表征及结构

用碳硼烷的含硒锂盐Li2Se2C2B10H10 (1)与单茂羰基铁的氯化物Cp′Fe(CO)2Cl(2)反应得到不对称型双核半夹心结构铁的化合物Cp′2Fe2(CO)3Se2C2B10H10(3). X射线单晶结构分析表明其中一个铁原子是手性的, 而且两个铁原子之间没有相互作用.     

Synthesis and crystal structure characterization of supramolecular complex [Cd2(Bipy)2(L)2(H2O)2] · 9H2O (H2L = 2,2′-bipyridyl-6,6′-dicarboxylic acid)

In the complex [Cd₂(Bipy)₂(L)₂(H₂O)₂] · 9H₂O, the center atom Cd(II) presents a seven-coordinated pentagonal bipyramidal geometry with seven coordination bonds, four Cd-N bonds, and three Cd-O bonds. X-ray structural analysis shows that nineteen water molecules formed a large water cluster, the cluster and the composition connected to form 2D plane areolar framework and 3D zigzag networks structure through π-π-stacking and hydrogen bonding. This composition in the previous report is rare.     

Investigation into the reactivity of oxoniobocene complexes [Cp*2Nb(O)R] (Cp*=η5-C5Me5; R=H,OH, OMe) towards heterocumulenes: formation of carbamato and thiocarbamato complexes and catalytic cyclization of PhNCO

The reaction of [Cp*₂NbCl₂] (Cp*=η⁵-C₅Me₅) with KOH or Ba(OH)₂·8H₂O in THF was investigated under slightly modified conditions. In addition to the known complex [Cp*₂Nb(O)H] (1), the new compound [Cp*₂Nb(O)OH] (2) was formed. The reaction of 2 with PhNCS gave yellow [Cp*₂Nb(O){SC(O)NHPh}] (3), while PhNCO formed yellow [Cp*₂Nb(O){OC(O)NHPh}] (4). Complexes 3 and 4 were analytically and spectroscopically characterized. X-ray diffraction analyses of both compounds show that they contain either η¹-S-thiocarbamato (3) or η¹-O-carbamato ligand (4) along with a terminal NbO group. The reaction of 1 with one equivalent of PhNCO mainly gave orange [Cp*₂NbH{OC(O)NPh}] (5) along with some 4. The molecular structure of 5 contains a niobocene unit comprising η²-N,O-carbamato chelate, which formally is a [2+2] cycloaddition product of the NbO group and the heterocumulene. A hydride ligand completes the coordination sphere around Nb. Reaction of 1 with excess PhNCO gave a mixture of heterocycles (PhNCO)₂ (6) and (PhNCO)₃ (7) in the approximate ratio 3:2. By contrast, the reaction of [Cp*₂Nb(O)OMe] with PhNCO in molar ratios from 1:3 to 1:100 gave nearly pure triphenylisocyanurate 7.     

Hydrothermal synthesis and structural characterization of a new one-dimensional ladder-shaped metal-organic framework Zn(HTci)(4,4′-bipy)0.5 · H2O (H3Tci = tri(2-carboxyethyl)isocyanurate, 4,4′-bipy = 4,4′-bipyridine)

A new metal-organic coordination polymer, namely, Zn(HTci)(4,4′-Bipy)_0.5 · H₂O (I) (H₃Tci = tri(2-carboxyethyl)isocyanurate, 4,4′-Bipy = 4,4′-bipyridine), has been synthesized under hydrothermal conditions by the reaction of zinc nitrate, H₃Tci, and 4,4′-Bipy with the presence of H₂O and characterized by elemental analysis, IR and X-ray single-crystal diffraction. The X-ray diffraction analysis reveals that I crystallizes in the triclinic system, $P\bar 1$ space group. The unit cell parameters for I: a = 5.248(1), b = 12.537(2), c = 14.597(2) Å, α = 91.91(1)°, β = 91.22(2)°, γ = 95.75(1)°, V = 954.8(3) ų, Z = 2.     

Addition of boranes to (E)-(η5-C5H5)2Zr(CH=CHPh)Cl

In this study, the addition of boranes to (E)-(η⁵-C₅H₅)₂Zr(CH=CHPh)Cl (3) has been examined in order to investigate the regioselectivity of these ‘hydroboration’ reactions. We have found that these additions proceed with remarkable selectivity to give exclusive formation of a saturated organic molecule where one carbon atom has both the boron and the zirconium fragments. These reactions do not proceed via a conventional hydroboration reaction, but instead go through an initial transmetalation step to generate (E)-(η⁵-C₅H₅)₂Zr(H)Cl (1) and the corresponding alkenyl boron intermediate, whereupon subsequent hydrozirconation of this latter species gives the geminal products. An x-ray diffraction study has been conducted on gem-(η⁵-C₅H₅)₂Zr(CH(Bpin)CH₂Ph)Cl (pin = 1, 2-O₂C₂Me₄) (2). Crystals of 2 were orthorhombic with a = 18.545(3) Å, b = 15.713(3) Å, c = 16.157(3) Å in the space group Pccn. An x-ray diffraction study has also been conducted on the trinuclear zirconium oxide species (η⁵-C₅H₅)₂ZrO₂[ZrCl(η⁵-C₅H₅)₂]₂ (4). Crystals of 4 were orthorhombic with a = 13.6000(8) Å, b = 14.2252(8) Å, c = 17.6500(10) Å in the space group P2(1)2(1)2(1).      

Syntheses and crystal structures of two Zn(II) complexes, [Zn(Fura)2(2,2′-bipy)(H2O)] and [Zn(μ-dnbc)2] (Fura=Furoic acid, 2,2′-bpy=2,2′-bipyridine,dnba=3,5-dinitrobenzoic acid)

Two Zn(II) complexes, [Zn(Fura)₂(2,2′-bpy)(H₂O)] (1) and [Zn(µ-dnbc)₂] (2), have been synthesized and characterized by X-ray diffraction and IR spectra. 1 is a quaternary Zn(II) complex with ZnN₂O₃ configuration distorted square pyramid geometry; 2 is a Zn(II) coordination polymer with 1D double-helical chains bridged by 3,5-dinitrobenzoic acid.