Synthesis and Characterization of Cerium Tetraphenylporphyrin Nitrate and Molecular Recognition for NO

Cerium （III） tetraphenylporphyrin nitrate Ce（TPP）NO3 was synthesized by using meso- tetraphenylporphyrin （TPP） and Ce（NO3）.6H20 in mixture solution of CHC13 and C2HsOH （V：V=1：1）. The complex was characterized by UV-Vis, FT-IR, conventional fluorescence, MALDI-TOF-MS, and ^1H NMR spectral techniques. The structure of complex was proposed viaSpectral analyses, in which tetraphenylporphyrin was coordinated to a cerium ion in a tetradentate fashion, while one nitrate was coordinated to the same cerium ion. After bubbling NO to the solution of Ce（TPP）NO3 in CH2Cl2, spectral analyses suggested that Ce（TPP）NO3 could interact with NO to form a novel complex of Ce（TPP）（NO）NO3, and NO was coordinated to the center cerium ion. When nitrogen was poured into the Ce（TPP）（NO）（NO3） solution, the complex could be reduced to Ce（TPP）NO3.     

A New Method of Synthesis of Azo Schiff Base Ligands with Azo and Azomethine Donors： Synthesis of N-4-Methoxybenzylidene-2-（3-hydroxyphenylazo）-5-hydroxyaniline and Its Nickel（Ⅱ） Complex

A new method for the synthesis of azo Schiff an base ligand in which the azo and azomethine groups are coordination sites was developed through a Schiff base precursor. The precursor, N-4-methoxybenzylidene-3-hydroxyphenylamine （SB） derived from 3-aminophenol was regioselectively coupled with a diazonium ion para to the hydroxyl group of the amine component of the Schiff base. The para selectivity was controlled by the directing effect of the hydroxyl group. The ligand and its nickel（Ⅱ） complex were characterized by elemental analyses, IR and UV-Vis spectroscopy. The analytical and spectral data supported the mononuclear formulation of the complex with metal to ligand ratio （M ： L = 1 ： 2） and suggested a square planar geometry for the complex.     

四氮大环-金属配合物与DNA作用的电化学及谱学研究

Mononuclear copper（Ⅱ）, nickel（Ⅱ） and cobalt（Ⅲ） tetracoordinate macrocyclic complexes were synthesized and spectroscopically characterized. The crystal structure of the three compounds were determined by X-ray crystallography. The electrochemical experimental results indicate that the three complexes could interact with DNA mainly by electrostatic interaction. The interaction of tetracoordinate macrocyclic cobalt（Ⅲ） complex with DNA was studied by cyclic voltammetry and UV-vis spectroscopy. The experimental results reveal that tetracoordinate macrocyc- lic cobalt（Ⅲ） complex could interact with DNA by electrostatic interaction to form a 1 ： 1 DNA association complex with a binding constant of 7.50 ×10^3 L·mol^-1.     

Polyethylenimine （PEI）-g-comb-poly（ethylene glycol）-transferrin（Ⅰ）： Tumor-targeted Vector for Gene Delivery In.vitro

The work described the synthesis and evaluation of PEI-g-comb-PEG-transferrin as a potential system for gene therapy in vitro. The MW of PEG was 10KDa, and PEI was 2KDa. Its structure was identified by NMR, FT-IR and TGA spectroscopy. MTT assay found that at concentration up to 4000 n mol/L of the polymer, cell viability was over 85%. The bio-character of polymer/DNA complex was characterized by agarose gel electrophoresis, ethidium bromide exclusion and zeta-potential assay. The polymer could retardate DNA at N/P ratio 3.0-3.5 （mol/mol）. The particle size of the polymer/DNA complex was less than 300 nm. Transfection efficiency of the complex was studied in COS7 and NT2 cell lines.     

Synthesis, Characterization and Properties of Tri-substitute Potassium Salt of Trinitrophloroglucinol

The title complex [K3（TNPG）·（H2O）2]n was synthesized by the reaction of the aqueous solutions of trinitrophlomglucinol （TNPG） with KHCO3. The complex was characterized by elemental analysis and FTIR spectroscopy, and its single crystal structure was determined by X-ray diffraction analysis. The structural analysis demonstrates that two different coordination modes of K cations [K（1） and K（2）] are around TNPG^3- anions in complex [Ka（TNPG）·（H2O）2]n, where the coordination numbers are eight. All K atoms coordinate with O atoms of phenolic hydroxyl group and nitro-group simultaneously. The thermolysis of the [Ka（TNPG） · （H2O）2]n has been investigated by using differential scanning calorimetry （DSC） and thermogravimetry-derivative thermogravimetry （TG-DTG） at a heating rate of 10 ℃/min. The thermal decomposition processes of the title complex were comprised of one endothermic dehydration stage and one exothermic decomposition stage in 270-320℃, and the final decomposition residue contained KNC. Impact and friction sensitivity results of the complex revealed its sensitive nature towards mechanical stimuli. The experiments verified that the complex has some characteristics of explosive.     

Synthesis, Crystal Structure and DNA Binding Studies of a Nickel（II） Complex with 2-Aminomethylbenzimidazole and Demethylcantharate

A new mixed-ligand nickel(Ⅱ) complex, [Ni(L)(DCA)(H2O)]·2H2O (L = C8H9N3, 2-aminomethyl-benzimidazole, DCA2- = 7-oxabicyclo[2,2,1]heptane-2,3-dicarboxylate, demethylcantharate, C8H8O5), has been synthesized and characterized. The structure of the complex was determined by single-crystal X-ray diffraction. It is of monoclinic system, space group P21/c with a = 7.7211(7), b = 12.0799(12), c = 19.7867(19), β = 100.390(6)°, V = 1815.2(3) nm3, Dc = 1.625 g·cm-3, Ζ = 4, F(000) = 928, R = 0.0314 and wR = 0.0822. In addition, the interaction between the complex and DNA was studied by means of fluorescence spectra and viscosity. The results indicate that the complex binds to DNA by the mode of partial intercalation with the Stern-Volmer constants Ksv of 3.81 × 104 mol·L-1.     

A New Method of Synthesis of Azo Schiff Base Ligands with Azo and Azomethine Donors: Synthesis of N-4-Methoxy- benzylidene-2-(3-hydroxyphenylazo)-5-hydroxy- aniline and Its Nickel(II) Complex

A new method for the synthesis of azo Schiff an base ligand in which the azo and azomethine groups are coordination sites was developed through a Schiff base precursor. The precursor, N-4-methoxybenzylidene-3-hydroxy- phenylamine (SB) derived from 3-aminophenol was regioselectively coupled with a diazonium ion para to the hydroxyl group of the amine component of the Schiff base. The para selectivity was controlled by the directing effect of the hydroxyl group. The ligand and its nickel(II) complex were characterized by elemental analyses, IR and UV-Vis spectroscopy. The analytical and spectral data supported the mononuclear formulation of the complex with metal to ligand ratio (M∶L＝1∶2) and suggested a square planar geometry for the complex.     

Antitumor Metallothiosemicarbazonate： Synthesis,Crystal Structure,Spectra and Antitumor Studies of Co（Ⅲ） Complex with Thiosemicarbazone Derivative of 2-Benzoylpyridine

The title complex [Co（L）2]Cl·4H2O I has been achieved via self-assembly by incorporating cobalt into 2-benzoylpyridine thiosemicarbazonate ligand, and characterized by elemental analysis, infrared spectra, mass spectra and single-crystal X-ray diffraction study. The crystal crystallizes in monoclinic, space group P2 1/n, with a = 10.227（3）, b = 17.363（4）, c = 17.459（4） A, β= 100.408（4）°, V= 3049.2（13） A^3, Z = 4, Mr = 677.08, Dc = 1.475 g/cm^3, μ（MoKα） = 0.834 mm^-1, F（000） = 1400, the final R = 0.0747 and wR = 0.0896 for 1663 observed reflections with I 〉 2σ（I）. The complex contains one six-coordinated cobalt ion connected by two thiosemicarbazone ligands which act as a tridentate ligand to coordinate with the center metal atoms via two pyridyl nitrogen atoms, two imine nitrogen atoms and two sulfur atoms giving rise to a mononuclear structure. Hydrogen bonds existing in the complex link the different components to stabilize the crystal structure. The antiturnor activity of the title complex was tested against A549 lung cancer cell line. Complex ! exhibits antitumor activity.     

Synthesis,Characterization and Application of Methyl 3,5-Disulfo-benzoate Dipotassium Dihydrate as Nucleating Agent for Poly（L-lactide）

A newly synthesized aromatic sulfonate compound,complex 2 with formula of K2[H3COOC-C6H3（SO3）2]·2H2O（methyl 3,5-disulfo-benzoate dipotassium dihydrate） was synthesized and characterized by elemental analysis,infrared（IR） spectrometry,nuclear magnetic resonance（NMR） and crystal structure measurement.Single-crystal X-ray diffraction（XRD） revealed that complex 2 crystallized in the triclinic system with space group P（i）.Complex 2 was used as nucleating agent for poly（L-lactide）（PLLA）.The crystallization of PLLA with powder of complex 2 was investigated by means of differential scanning calorimetry（DSC） and polarized optical microscopy （POM）.The results prove that complex 2 was effective as nucleating agent for PLLA.It could accelerate crystallization by reducing the induction time and increasing the density of nuclei in the crystallization process.The half-time of crystallization（t0.5） for pure PLLA was about 8 times longer than that of PLLA sample with 1.0％（mass fraction） of complex 2.     

钐(Ⅲ)与不对称希夫碱配合物的合成、表征和热分解反应动力学

A new unsymmetrical Schiff base zwitterion （Ⅲ） was synthesized using L-lysine, salicylaldehyde and 2-hydroxy-l-naphthaldehyde. Samarium（Ⅲ） complex of this ligand [SmL（NO3）]NO3·2H2O has been prepared and characterized by elemental analyses, IR, UV and molar conductance. The thermal decomposition kinetics of the complex for the second stage was studied under non-isothermal condition by TG and DTG methods. The kinetic equation may be expressed as dα/dt=3/2Ae^E/RT（1-α）^2/3[1-（1 -α）^1/3）]^-1. The kinetic parameters （E, A）, activation entropy △S^x and activation free-energy △G^x were also gained.     

Metal complexes of sterically hindered pyrzolylpyridines. The single crystal X-ray structure of [Cu(L)2]BF4 (L = 1-{pyrid-2-yl}-3-{2′,5′-dimethoxyphenyl}pyrazole)

Reaction of potassium 3{5}-(3′,4′-dimethoxyphenyl)pyrazolide with 2-bromopyridine in diglyme at 130°C for 3 days followed by an aqueous quench, affords 1-{pyrid-2-yl}-3-{3′,4′-dimethoxyphenyl}pyrazole (L²) in 69% yield after recrystallization from hot hexanes. Complexation of [Cu(NCMe)₄]BF₄ by 2 molar equivalents of 1-{pyrid-2-yl}-3-{2′,5′-dimethoxyphenyl}pyrazole (L¹) or L² in MeCN at room temperature, followed by concentration and crystallisation with Et₂O, gives [Cu(L)₂]BF₄ L = L¹, L²) in good yields. Treatment of AgBF₄ with L¹ or L² in MeNO₂ similarly gives [Ag(L)₂]BF₄ L = L¹, L²); reaction of AfBF₄ with L² in MeCN gives a product of stoichiometry [Ag(L²)(NCMe)]BF₄. The ¹H NMR spectra of the [M(L)₂]BF₄ complexes show peaks arising from a single coordinated environment. The single crystal X-ray structure of [Cu(L¹)₂]BF₄ shows a tetrahedral complex cation with Cu---N = 2.011(8), 2.036(8), 2.039(8), 2.110(8) Å. The Cu^I centre is close to tetrahedral, the dihedral angle between the least-squares planes formed by the Cu atom and the N donor atoms of the two ligands being 88.3(3)°. Complexation of hydrated Cu(BF₄)₂ by L² in MeCN at room temperature yields [Cu(L₂)₂](BF₄)₂. The cyclic voltammograms of the three Ag^I complexes in MeCN/0.1 M Bu₄ⁿ NPF₆ are suggestive of extensive ligand dissociation in this solvent.     

新型二维网状双席夫碱银配合物的合成与结构

席夫碱配体由于在合成上具有极大的灵活性和良好的配位能力 ,因而席夫碱 -金属配合物的研究一直受到广泛重视 .多年来 ,席夫碱配体由简单的单齿发展到多齿和大环配体 .此外 ,过渡金属的席夫碱配合物具有独特的结构、性能和广泛的应用 ,如氧化还原 [1] 、催化 [2 ] 以及生物体系的化学模拟 [3 ] ;另一方面 ,由于银原子配位方式的多样性 (二、三、四和五配位 ) ,便于人们对超分子化合物的组装规律进行系统研究 ,因而银配合物的研究正日益引起人们极大的兴趣 [4～ 7] .鉴于此 ,我们设计合成了一个新的四齿席夫碱配体 L ,研究了其与 CF3 SO3 …     

一种双吡啶双酰胺配体修饰的Keggin型硅钼酸盐基配合物的合成、结构与催化性能

水热反应条件下制备了一个基于半刚性双吡啶双酰胺配体3-bpcd(N,N'-双(3-吡啶)环己烷-1,4-双甲酰胺)和Keggin型多金属氧酸盐的银配合物{[Ag₂(3-bpcd)₃][Ag(3-bpcd)(SiMo₁₂O₄₀)]₂(3-H₂bpcd)₂}·7H₂O,并通过红外光谱、元素分析和X射线单晶衍射等技术手段确定了其晶体结构。结构分析表明该配合物属于三斜晶系,P-1空间群,晶胞参数a=1.3597(5) nm,b=1.4949(5) nm,c=2.5249(10) nm,α=88.998(6)°,β=88.856(7)°,γ=67.458(6)°,V=4.739(3) nm³,M_r=6471.02,D_c=2.261 g/cm³,Z=1,S=0.955,F(000)=3124,R₁=0.0768,wR₂=0.1936。 配合物是由一维[Ag(3-bpcd)(SiMo₁₂O₄₀)]₂^6-链、双金属[Ag₂(3-bpcd)₃]²⁺结构单元、2个未配位的质子化有机配体3-H₂bpcd和7个结晶水共同组成的复杂结构,多种结构单元间通过氢键作用形成三维超分子网络结构。 标题配合物修饰的碳糊电极对NO₂^-有好的电催化还原活性,此配合物作为催化剂对罗丹明B的降解有显著的催化效果。 CCDC:1401875     

The lively chemistry of the di-μ-methylene-bis(pentamethylcyclopentadienyl-rhodium) complexes, analogues of surface reactions in heterogeneous catalysis

The chemistry of the di-μ-methylene-bis(pentamethylcyclopentadienyl-rhodium) complexes is reviewed. The complex [{(η⁵-C₅Me₅)RhCl₂}₂] (1a) reacted with MeLi to give, after oxidative work-up, blood-red cis-[{(η⁵-C₅Me₅)Rh(μ-CH₂)}₂(Me)₂], 2. This has the two rhodiums in the +4 oxidation state (d⁵), and linked by a metal-metal bond (2.620 Å). Trans-2 was formed on isomerisation of cis-2 in the presence of Lewis acids, or by direct reaction of 1a with Al₂Me₆, followed by dehydrogenation with acetone. The Rh-methyls in [{(η⁵-C₅Me₅)Rh(μ-CH₂)}₂(Me)₂] were readily replaced under acidic conditions (HX) to give [{(η⁵-C₅Me₅)Rh(μ-CH₂)}₂(X)₂] (X = Cl, Br or I); these latter complexes reacted with a variety of RMgX to give [{(η⁵-C₅Me₅)Rh(μ-CH₂)}₂(R)₂] (R = alkyl, Ph, vinyl, etc.). Trans-2 also reacted with HBF₄ in the presence of L to give first [{(η⁵-C₅Me₅)Rh(μ-CH₂)}₂(Me)(L)]⁺ and then [{(η⁵-C₅Me₅)Rh(μ-CH₂)}₂(L)₂]²⁺ (L = MeCN, CO, etc.). The {(η⁵-C₅Me₅)Rh(μ-CH₂)}₂ core is rather kinetically inert and also forms a variety of complexes with oxy-ligands, both cis-, e.g. [{(η⁵-C₅Me₅)Rh(μ-CH₂)}₂(μ-OAc)]⁺ and trans-, such as [(η⁵-C₅Me₅)Rh(μ-CH₂)}₂(H₂O)₂]²⁺. The complexes [{(η⁵-C₅Me₅)Rh(μ-CH₂)}₂(R)L]⁺ (R = Me or aryl) in the presence of CO, or [{(η⁵-C₄Me₅)Rh(μ-CH₂)}₂(R)₂] (R = Me, Ph or CO₂Me) in the presence of mild oxidants, readily yield the C---C---C coupled products RCH=CH₂. The mechanisms of these couplings have been elucidated by detailed labelling studies: they are more complex than expected, but allow direct analogies to be drawn to C---C couplints that occur during Fischer-Tropsch reactions on rhodium surfaces.     

Synthesis of novel platinum-silver and platinum-copper complexes with bridging alkynyl ligands

The study of the reactivity of [Pt₂M₄(CCR)₈] (M=Ag or cu; R=Ph or ^tBu) towards different neutral and anionic ligands is reported. This study reveals that reactions of the phenylacetylide derivatives [Pt₂M₄(CCPh)₈] with anionic, X⁻ (X=Cl or Br) or neutral donors (CN^tBu or py) in a molar ratio 1:4 (m/donor ratio 1:1) yield the trinuclear anionic (NBu₄)₂[{Pt(CCPh)₄ (MX)₂] (M=Ag or Cu, X =Cl or Br) or neutral [{Pt(CCPh0₄=sAGL)₂] (L=CN^tBu or py) complexes, respectively. The crystal structure of (NBu₄)₂[{Pt(CCPh)₄}(CuBr)₂](4) shows that the anion is formed by a dianionic Pt(CCPh)₄ fragment and two neutral CuBr units joined through bridging alkynyl ligands. All the alkynyl groups are σ bonded to Pt and η²-coordinated to a Cu atom which have an approximately trigonal-planar geometry. By contrast, similar reactions with [Pt₂M₄(CC^tBu)₈] (molar ratio M/donor 1:1) afford hexanuclear dianionic (NBu₄)₂[Pt₂M₄(CC^tBu)₈X₂] or neutral [Pt₂Ag₄(CC^tBu0₈Py₂]. Only by treatment with a large exces of Br ⁻ (molar ratio M/Br⁻ 1:2) are the trinuclear complexes (NBu₄)₂[{Pt(CC^tBu₄ (MBr)₂] (M=Ag, Cu) obtained. Attempted preparations of analogous complexes with phosphines (L′=PPh₃ or PEt₃) by reactions of [Pt₂M₄(CCR₈] with L′ leads to displacement of alkynyl ligands from platinum and formation of neutral mononuclear complexes [trans-Pt(CCR)₂L′₂].     

Synthesis, structure and hydrogenation catalytic activity of [Ru3(μ3,η-ampy)(μ,η:η-PhC=CHPh)(CO)6(PPh3) (Hampy = 2-amino-6-methylpyridine)

The compound [RU₃(μ₃,η²- -ampy)(μ₃η¹:η²-PhC=CHPh)(CO)₆(PPh₃)₂] (1) (ampy = 2-amino-6-methylpyridinate) has been prepared by reaction of [RU₃(η-H)(μ₃,η²- ampy) (μ,η¹:η²-PhC=CHPh)(CO)₇(PPh₃)] with triphenylphosphine at room temperature. However, the reaction of [RU₃(μ-H)(μ₃, η² -ampy)(CO)₇(PPh₃)₂] with diphenylacetylene requires a higher temperature (110°C) and does not give complex 1 but the phenyl derivative [RU₃(μ₃,η²-ampy)(μ,η ¹:η² -PhC=CHPh)(μ,-PPh₂)(Ph)(CO)₅(PPh₃)] (2). The thermolysis of complex 1 (110°C) also gives complex 2 quantitatively. Both 1 and 2 have been characterized by0 X-ray diffraction methods. Complex 1 is a catalyst precursor for the homogeneous hydrogenation of diphenylacetylene to a mixture of cis- and trans -stilbene under mild conditions (80°C, 1 atm. of H₂), although progressive deactivation of the catalytic species is observed. The dihydride [RU₃(μ-H)₂(μ ₃,η²-ampy)(μ,η¹:η²- PhC=CHPh)(CO)₅(PPh₃)₂] (3), which has been characterized spectroscopically, is an intermediate in the catalytic hydrogenation reaction.     

Substituted cyclopentadienyl ligands—10. Intramolecular steric interactions in [(η-C5H3(SiMe3)2)Mo(CO)2(L)I]

Reaction of C₅H₄(SiMe₃)₂ with Mo(CO)₆ yielded [(η⁵-C₅H₃(SiMe₃)₂)Mo(CO)₃]₂, which on addition of iodine gave [(η⁵-C₅H₃(SiMe₃)₂Mo(CO)₃I]. Carbonyl displacement by a range of ligands: [L = P(OMe)₃, P(OPrⁱ)₃,P(O-o-tol)₃, PMe₃, PMe₂Ph, PMePh₂, PPh₃, P(m-tol)₃] gave the new complexes [(η⁵-C₅H₃(SiMe₃)₂ MO(CO)₂(L)I]. For all the trans isomer was the dominant, if not exclusive, isomer formed in the reaction. An NOE spectral analysis of [(η⁵-C₅H₃(SiMe₃)₂)Mo(CO)₂(L)I] L = PMe₂Ph, P(OMe)₃] revealed that the L group resided on the sterically uncongested side of the cyclopentadienyl ligand and that the ligand did not access the congested side of the molecule. Quantification of this phenomenon [L = P(OMe)₃] was achieved by means of the vertex angle of overlap methodology. This methodology revealed a steric preference with the trans isomer (less congestion of CO than I with an SiMe₃ group) being the more stable isomer for L = P(OMe)₃.     

Multiple ligand transfer reaction between [CpRu(L)(AN)2][PF6] (L=AN, CO, P(OMe)3; AN=acetonitrile) and CpFe(CO)L′X (L′=CO, PMe3, PMe2Ph, PMePh2, PPh3, P(OPh)3; X=Cl, Br, I)

Treatment of ruthenium complexes [CpRu(AN)₃][PF₆] (1a) (AN=acetonitrile) with iron complexes CpFe(CO)₂X (2a–2c) (X=Cl, Br, I) and CpFe(CO)L′X (6a–6g) (L′=PMe₃, PMe₂Ph, PMePh₂, PPh₃, P(OPh)₃; X=Cl, Br, I) in refluxing CH₂Cl₂ for 3 h results in a triple ligand transfer reaction from iron to ruthenium to give stable ruthenium complexes CpRu(CO)₂X (3a–3c) (X=Cl, Br, I) and CpRu(CO)L′X (7a–7g) (L′=PMe₃, PMe₂Ph, PMePh₂, PPh₃, P(OPh)₃; X=Br, I), respectively. Similar reaction of [CpRu(L)(AN)₂][PF₆] (1b: L=CO, 1c: P(OMe)₃) causes double ligand transfer to yield complexes 3a–3c and 7a–7h. Halide on iron, CO on iron or ruthenium, and two acetonitrile ligands on ruthenium are essential for the present ligand transfer reaction. The dinuclear ruthenium complex 11a [CpRu(CO)(μ-I)]₂ was isolated from the reaction of 1a with 6a at 0°C. Complex 11a slowly decomposes in CH₂Cl₂ at room temperature to give 3a, and transforms into 7a by the reaction with PMe₃.     

Reactions of the cationic diruthenium carbonyl complex [Ru2(μ-dppm)2(CO)4(μ,η-O2CMe)] with bidentate ligands; intramolecularly assisted stereospecific synthesis via the second-sphere face-to-face π–π stacking interactions

The reactions of the diruthenium carbonyl complexes [Ru₂(μ-dppm)₂(CO)₄(μ,η²-O₂CMe)]X (X=BF₄⁻ (1a) or PF₆⁻ (1b)) with neutral or anionic bidentate ligands (L,L) afford a series of the diruthenium bridging carbonyl complexes [Ru₂(μ-dppm)₂(μ-CO)₂(η²-(L,L))₂]X_n ((L,L)=acetate (O₂CMe), 2,2′-bipyridine (bpy), acetylacetonate (acac), 8-quinolinolate (quin); n=0, 1, 2). Apparently with coordination of the bidentate ligands, the bound acetate ligand of [Ru₂(μ-dppm)₂(CO)₄(μ,η²-O₂CMe)]⁺ either migrates within the same complex or into a different one, or is simply replaced. The reaction of [Ru₂(μ-dppm)₂(CO)₄(μ,η²-O₂CMe)]⁺ (1) with 2,2′-bipyridine produces [Ru₂(μ-dppm)₂(μ-CO)₂(η²-O₂CMe)₂] (2), [Ru₂(μ-dppm)₂(μ-CO)₂(η²-O₂CMe)(η²-bpy)]⁺ (3), and [Ru₂(μ-dppm)₂(μ-CO)₂(η²-bpy)₂]²⁺ (4). Alternatively compound 2 can be prepared from the reaction of 1a with MeCO₂H–Et₃N, while compound 4 can be obtained from the reaction of 3 with bpy. The reaction of 1b with acetylacetone–Et₃N produces [Ru₂(μ-dppm)₂(μ-CO)₂(η²-O₂CMe)(η²-acac)] (5) and [Ru₂(μ-dppm)₂(μ-CO)₂(η²-acac)₂] (6). Compound 2 can also react with acetylacetone–Et₃N to produce 6. Surprisingly [Ru₂(μ-dppm)₂(μ-CO)₂(η²-quin)₂] (7) was obtained stereospecifically as the only one product from the reaction of 1b with 8-quinolinol–Et₃N. The structure of 7 has been established by X-ray crystallography and found to adopt a cis geometry. Further, the stereospecific reaction is probably caused by the second-sphere π–π face-to-face stacking interactions between the phenyl rings of dppm and the electron-deficient six-membered ring moiety of the bound quinolinate (i.e. the N-included six-membered ring) in 7. The presence of such interactions is indeed supported by an observed charge-transfer band in a UV–vis spectrum.     

Synthesis, structure and reactions of seven-coordinate, phosphine-supported, halide-activated carbonyl- and alkyne-complexes of niobium(I)

The complexes (Hal)Nb(CO)₃(PR₃)₃ (PR₃ = PEt₃, Hal = I; PR₃ = PMe₂Ph, Hal = Cl, Br, I) and (Hal)Nb(CO)_4/2(dppe)_1/2 (Hal = Br, I) have been prepared by oxidative halogenation of carbonylniobate with pyridinium halides (Hal = Cl, Br) or iodine (Hal = I). In the tricarbonyls, one CO and one PR₃ are labile and can be displaced by a four-electron donating alkyne to give all-trans-[(Hal)Nb(CO)₂(RCCR′)(PR₃)₂] (PR₃ = PMe₂Ph; Hal = Cl, Br, I: R, R′ = H, Et, Ph; R = H, R′ = Ph. PR₃ = PEt₃, Hal = I: R, R′ = Pr; R = H, R′ = Bu, Ph; R = Me, R′ = Et). In the case of acetylene, INb(CO)(HCCH)₂(PEt₃)₂ is also formed. PR₃ can be displaced by P(OMe) ₃. In the tetracarbonyls, two CO ligands are replaced by two isonitriles to form INb(CO)₂(CNR)₂dppe (R = ^tBu, Cy), or by one alkyne to form (Hal)Nb(CO)₂(PhCCPh)dppe (Hal = Br, I). In these complexes, the remaining CO ligands occupy cis positions. The structure of BrNb(CO)₂(dppe)₂·THF, INb(CO)₂(dppe)₂·hexane and INb(CO)₂(PEt₃)₂(MeCCEt) have been determined by a single crystal X-ray diffraction study. The alkyne complexes are best regarded as octahedral with the centre of the alkyne ligand occupying the positions trans to the halide and the CC axis aligned with the OC---Nb---CO axis. The complexes (Hal)Nb(CO)₂(dppe)₂ adopt a trigonal prismatic structure with the halide capping the tetragonal face spanned by the four phosphorus functions. The crystal structure of a by-product, Br₂Nb(CO)(H₂CPhPCH₂CH₂PPh₂)₂·1/2THF has also been determined. The geometry is pentagonal bipyramidal, with one of the bromine atoms and the CO on the axis. Some ⁹³ Nb NMR data for the Nb^I complexes are presented, and preliminary observations on the reactions between the π-alkyne complexes and H₂ or H⁻ are reported.