A spectrophotometric and thermodynamic study of the sitting-atop complex formation from reaction between free base meso-tetraarylporphyrins and zirconyl nitrate in chloroform solution

The sitting-atop complexation of meso-tetraarylporphyrins and its para-substituted derivatives (H₂t(4-X)pp, X:H, Br, Cl, CH(CH₃)₂, OCH₃, CH₃), as electron donors, with zirconyl, as an electron acceptor, have been investigated spectrophotometrically in chloroform. The mole ratio studies based on physicochemical techniques were employed clearly and revealed the formation of 1:1 sitting-atop complexes which was confirmed by UV–vis, ¹H NMR and IR spectroscopic data. The value of the formation constant was estimated for each complex using a nonlinear optimization of the complex absorbance vs. mole ratio data by package KINFIT. The results showed that the stability of these complexes decreases with the temperature enhancement. Thermodynamic parameters, ΔG°, ΔH° and ΔS°, of the SAT complexes have been determined from the temperature dependence of formation constants by Van’t Hoff equation. Also, the influence of the substituents of the aryl rings in H₂t(4-X)pp on the stability of the SAT complexes is discussed.     

螺桨烷型分子BX[(CH_2)_n]_3和BX(CH_2)[CH(CH_2)_nCH](X=N,P)的结构和性质

采用密度泛函理论(DFT)研究了螺桨烷型分子BX[(CH2)n]3和BX(CH2)[CH(CH2)n CH](X=N,P;n=1-6)的结构、稳定性、化学键和电子光谱性质.计算结果表明这些分子都是稳定的.BX[(CH2)n]3(X=N,P;n=1-6)的最高占据分子轨道(HOMO)和最低空分子轨道(LUMO)之间的能隙均大于5.20 eV,其中BN[CH2]3和BP[CH2]3的能隙超过7.0 eV,与C5H6的能隙(7.27 eV)很接近,BX(CH2)[CH(CH2)n CH](X=N,P;n=1-6)的能隙在6.80 eV左右.所研究分子能量的二阶差分表明BN[(CH2)3]3、BP[(CH2)4]3及BX(CH2)[CH(CH2)2CH](X=N,P)是最稳定的.BX[(CH2)n]3的Wiberg键级表明除了BN[(CH2)n]3(n=2和6)中不存在B―N键,其它化合物中B和N均形成了化学键,BP[(CH2)n]3中除了BP[(CH2)2]3不存在B―P键,其它的均存在.电子密度的拓扑分析表明N―B键属于离子键,而P―B键具有共价键特征.BX[(CH2)n]3(X=N,P)的第一垂直激发能分别在191.1-284.8 nm和191.8-270.1 nm之间,BX(CH2)[CH(CH2)n CH](X=N,P)的第一垂直激发能分别在190.5-199.7 nm和209.0-221.3 nm之间.     

Crystal structures and spectroscopic properties of copper(II) pseudohalide complexes with two sparteine epimers, having a CuN4 chromophore

Tetrahedrally distorted copper(II) sparteine pseudohalide complexes having a CuN₄ chromophore were prepared and characterized by various spectroscopic techniques and X-ray crystallography. Among them, the crystal structures of copper(II) isothiocyanate complexes with two sparteine epimers, (−)-l-sparteine (Sp) and (−)-α-isosparteine (α-Sp), were determined. The N_Sp–Cu–N_Sp plane in copper(II) (−)-l-sparteine isothiocyanate [Cu(Sp)(NCS)₂] and copper(II) (−)-α-isosparteine isothiocyanate [Cu(α-Sp)(NCS)₂] is twisted by 58.2(6)° and 52.2(9)°, respectively, from the N_NCS–Cu–N_NCS plane. Based on the values of the dihedral angles and tilted distances of these two complexes, the geometry around Cu(II) in Cu(α-Sp)(NCS)₂ is more distorted from the perfect tetrahedron than that in Cu(Sp)(NCS)₂. For copper(II) sparteine pseudohalide (NCS⁻ and N₃⁻) complexes having a CuN₄ chromophore, the EPR and the optical spectral data were collected. The results of X-ray crystallography and ESR spectroscopy are in a good agreement with the assumption that the degree of distortion from planarity to tetrahedron will reduce the A_|| value of four-coordinate copper(II) sparteine pseudohalide complexes.     

Hydrothermal Synthesis and Crystal Structure of [(CH3NH3)1.03K2.97]Sb12S20·1.34H2O

A novel thioantimonate(III) [(CH₃NH₃)_1.03K_2.97]Sb₁₂S₂₀·1.34H₂O was synthesized hydrothermally. It crystallizes in space groupP , witha=11.9939(7) Å,b=12.8790(8) Å,c=14.9695(9) Å,α=100.033(1)°,β=99.691(1)°,γ=108.582(1)°,V=2095.3(2) ų, andZ=2. The structure is determined from single crystal X-ray diffraction data collected at room temperature and refined toR(F)=0.037. In the crystal structure, each Sb(III) atoms has short bonds (2.37–2.58 Å) to three S atoms. The pyramidal [SbS₃] groups share common S atoms forming two types of centrosymmetric [Sb₁₂S₂₀] rings with the same topology. These rings are interconnected by weaker Sb–S bonds (2.92–3.29 Å) into 2-dimensional layers. Adjacent layers are parallel with K⁺and CH₃NH⁺₃ions and H₂O molecules located between them. Variation of bond valence sums calculated for the Sb(III) cations is found to be correlated with the coordination geometry. This is interpreted as due to the stereochemical activity of their lone electron pairs.     

Determination of the bond-angle distribution in vitreous B2O3 by B double rotation (DOR) NMR spectroscopy

The B–O–B bond angle distributions for both ring and non-ring boron sites in vitreous B₂O₃ have been determined by ¹¹B double rotation (DOR) NMR and multiple-quantum (MQ) DOR NMR. The [B₃O₆] boroxol rings are observed to have a mean internal B–O–B angle of 120.0±0.7° with a small standard deviation, σ_R=3.2±0.4°, indicating that the rings are near-perfect planar, hexagonal structures. The rings are linked predominantly by non-ring [BO₃] units, which share oxygens with the boroxol ring, with a mean B_ring–O–B_non-ring angle of 135.1±0.6° and σ_NR=6.7±0.4°. In addition, the fraction of boron atoms, f, which reside in the boroxol rings has been measured for this sample as f=0.73±0.01.     

Bis{2‐[(phenylimino)ethyl]‐1H‐pyrrol‐1‐ido‐κ2N,N′}nickel(II): a supramolecular structure formed by C—H...π hydrogen bonds

In the title compound, [Ni(C₁₂H₁₁N₂)₂], the Ni^II cation lies on an inversion centre and has a square‐planar coordination geometry. This transition metal complex is composed of two deprotonated N,N′‐bidentate 2‐[(phenylimino)ethyl]‐1H‐pyrrol‐1‐ide ligands around a central Ni^II cation, with the pyrrolide rings and imine groups lying trans to each other. The Ni—N bond lengths range from 1.894 (3) to 1.939 (2) Å and the bite angle is 83.13 (11)°. The Ni—N(pyrrolide) bond is substantially shorter than the Ni—N(imino) bond. The planes of the phenyl rings make a dihedral angle of 78.79 (9)° with respect to the central NiN₄ plane. The molecules are linked into simple chains by an intermolecular C—H...π interaction involving a phenyl β‐C atom as donor. Intramolecular C—H...π interactions are also present.     

Micellization behavior of [C16-12-C16], 2Br gemini surfactant in binary aqueous-solvent mixtures

The micellization behavior of bis cationic gemini surfactant, N,N′-dihexadecyl-N,N,N′,N′-tetramethyl-1,12-dodecanediammonium dibromide [C₁₆H₃₃N⁺(CH₃)₂-(CH₂)₁₂-N⁺(CH₃)₂C₁₆H₃₃, 2Br⁻] has been studied in binary aqueous mixtures of dimethyl sulfoxide, methanol, 1,4-dioxane, glycerol and ethylene glycol by conductivity and surface tension measurements at 300 K. The critical micellar concentration, degree of micelle ionization (α), surface excess concentration (Г_max), minimum surface area per molecule of surfactant (A_min), Gibbs free energy of micellization (ΔG_m°), the surface pressure at cmc (π_cmc), and the Gibbs energy of adsorption (ΔG_ad°) of the gemini surfactant have also been determined. The cmc, α, A_min increases where as (ΔG_m°), Г_max, and π_cmc decreases with increasing volume percentage of the solvents in the solvent–water binary mixture. The interfacial properties of the gemini surfactant, solute–solute, solvent–solute interactions and the effectiveness of a surface-active molecule in binary solvent systems have been discussed.     

A novel 18-metallacrown-6 complex: Synthesis, structural characterization and magnetic properties

The novel 18-metallacrown-6 complex, with the formula of [Mn₆(C₁₁H₁₁N₂O₃)₆(CH₃CH₂OH)₆]·3C₃H₇NO·2CH₃CH₂OH (1) (pmshz = N-propanoyl-3-methyl-salicylhydrazide), has been prepared and characterized. The self-assembled, manganese complex assumes a nearly planar cyclic structure with an [Mn–N–N]₆ backbone. Due to the coordination, the ligand enforces the stereochemistry of the Mn³⁺ ions as a propeller shape with alternating …ΔΛΔΛ… configurations. The magnetic properties of the metallacrown molecule are characterized by a weak antiferromagnetic exchange interaction between the Mn³⁺ ion spins with S = 2 in the cyclic system.     

Molecular structure of some [1.1 ]ferrocenylruthenocenophanium (n = 1,2 polyiodides salts

Oxidation of [1.1]ferrocenylruthenocenophane with a large excess and 1.5 equivalents of iodine gives dicationic iodo[1.1]ferrocenylruthenocenophanium²⁺I₃⁻ · 0.5I₂2 (1) and monocationic [1.1]ferrocenylruthenocenophanium⁺I₃⁻ (2) salts respectively. The structures of 1 and 2 were analyzed by single-crystal X-ray diffraction studies. The crystal form of 1 is monoclinic space group C2/c, A = 21.35](5), B = 20.594(5), C = 17.397(4) Å, β = 124.17(1)°, Z = 8, and the final R = 0.068 and R_w = 0.070. The cation formulated as [Fe^III(C₅H₄CH₂C₅H₄)₂Ru^IVI]²⁺ exists in a syn-conformation as in the cases of the neutral compound. The distance between the Ru^IV and Fe^II is 4.656(4) Å, which is much shorter than the value of the neutral compound (4.792(2) Å), and the bond angle of I---Ru^IV,Fe^III is 81.26°. The dihedral angle between the two η⁵-C₅H₄ (fulvenide) rings on the Ru^IV moiety is 37.56° due to the Ru^IV---I bond (2.758(3) Å). These two rings of Fe^III and Ru^IV moieties are essentially eclipsed. The unit cell has three kinds of I₃⁻ (I_3a⁻, I_3b⁻ and I_3c⁻) and one I₂, and the formula of 1 is given as [Fe^III(C₅H₄CH₂CSH₄)₂Ru^IVI]²⁺I₃⁻ · 0.5(I₃⁻)₂ · 0.5I₂. The crystal of 2 formulated as [Fe^III(C₅H₄CH₂C₅H₄)₂Ru^II]⁺I₃⁻ is triclinic space group

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, and the final R = 0.067 and R_w = 0.068. The unit cell has two independent molecules (unit A and B); i.e. two kinds of distance between the Ru^II and Fe^III, are observed; one (A) is 4.615(3) and the other (B) is 4.647(3) α. The two η⁵-C₅H₄ rings of both Fe^III and Ru^II are essentially staggered and the dihedral angles between the rings of FcH and RcH moieties are less than 5.8°. Typical ferrocenium-type broad singlet ⁵⁷Fe-Mössbauer lines are observed for both salts (1, 2) at all temperatures.     

Coordination behaviour of the 2‐(N,N‐dimethylaminomethyl)phenyl ligand towards the di‐t‐butylchlorotin(IV) moiety

{2‐(N,N‐Dimethylaminomethyl)phenyl}(di‐t‐butyl)tin(IV)chloride, {2‐[(CH₃)₂NCH₂]C₆H₄}Sn(t‐Bu)₂ Cl, has been prepared and characterized using NMR and crystallography. This is the first example of a triorganotin(IV) halide containing the 2‐[(CH₃)₂NCH₂]C₆H₄—group as a C,N‐chelating ligand with a weak intramolecular Sn—N interaction because of the steric hindrance of t‐butyl groups. The interatomic Sn—N distance is elongated to 2.904(14) Å and the central tin atom is distorted trigonal bipyramidal. Copyright © 2004 John Wiley & Sons, Ltd.     

Coordination‐directed one‐dimensional coordination polymers generated from a new oxadiazole bridging ligand and HgX2 (X = Cl,Br and I)

A new 1,3,4‐oxadiazole bridging bent organic ligand, 2,5‐bis{5‐methyl‐2‐[(4‐pyridyl)methoxy]phenyl}‐1,3,4‐oxadiazole, C₂₈H₂₄N₄O₃, L, has been used to create three novel one‐dimensional isomorphic coordination polymers, viz. catena‐poly[[[dichloridomercury(II)]‐μ‐2,5‐bis{5‐methyl‐2‐[(4‐pyridyl)methoxy]phenyl}‐1,3,4‐oxadiazole] methanol monosolvate], {[HgCl₂(C₂₈H₂₄N₄O₃)]·CH₃OH}_n, catena‐poly[[[dibromidomercury(II)]‐μ‐2,5‐bis{5‐methyl‐2‐[(4‐pyridyl)methoxy]phenyl}‐1,3,4‐oxadiazole] methanol monosolvate], {[HgBr₂(C₂₈H₂₄N₄O₃)]·CH₃OH}_n, and catena‐poly[[[diiodidomercury(II)]‐μ‐2,5‐bis{5‐methyl‐2‐[(4‐pyridyl)methoxy]phenyl}‐1,3,4‐oxadiazole] methanol monosolvate], {[HgI₂(C₂₈H₂₄N₄O₃)]·CH₃OH}_n. The free L ligand itself adopts a cis conformation, with the two terminal pyridine rings and the central oxadiazole ring almost coplanar [dihedral angles = 5.994 (7) and 9.560 (6)°]. In the Hg^II complexes, however, one of the flexible pyridylmethyl arms of ligand L is markedly bent and helical chains are obtained. The Hg^II atom lies in a distorted tetrahedral geometry defined by two pyridine N‐atom donors from two L ligands and two halide ligands. The helical chains stack together via interchain π–π interactions that expand the dimensionality of the structure from one to two. The methanol solvent molecules link to the complex polymers through O—H...N and O—H...O hydrogen bonds.     

The O–H···O, O–H···N and C–H···O hydrogen bonds in 1,4-dimethylpiperazine mono-betaine monohydrate

1,4-Dimethylpiperazine mono-betaine (1-carboxymethyl-1,4-dimethylpiperazinium inner salt, MBPZ) crystallizes as monohydrate. The crystals are orthorhombic, space group Pccn. Two MBPZ molecules and two water molecules form a cyclic oligomer, (MBPZ·H₂O)₂. The O–H···O and O–H···N hydrogen bonds are of 2.769(1) and 2.902(1) Å, respectively. The dimers interact with the neighboring molecules through the C–H···O hydrogen bonds of 3.234(1) Å. The piperazine ring assumes a chair conformation with the N(4)–CH₃ and N⁺(1)–CH₂COO⁻ groups in the equatorial position and the N⁺(1)–CH₃ group in the axial one. The FTIR spectrum is compared with that calculated by the B3LYP/6-31G(d,p) level of theory.     

Synthesis, structure and DNA binding studies of mononuclear copper(II) complexes with mixed donor macroacyclic ligands, 2,6-bis({N-[2&3-(phenylselenato)alkyl]}benzimidoyl)-4-methylphenol

Two new phenol based macroacyclic Schiff base ligands, 2,6-bis({N-[2-(phenylselenato)ethyl]}benzimidoyl)-4-methylphenol (bpebmpH, 1) and 2,6-bis({N-[3-(phenylselenato)propyl]}benzimidoyl)-4-methylphenol (bppbmpH, 2) of the Se₂N₂O type have been prepared by the condensation of 4-methyl-2,6-dibenzoylphenol (mdbpH) with the appropriate (for specific reactions) phenylselenato(alkyl)amine. These ligands with Cu(II) acetate monohydrate in a 2:1 molar ratio in methanol form complexes of the composition [(C₆H₂(O)(CH₃){(C₆H₅)CN(CH₂)_nSe(C₆H₅)}{(C₆H₅)CO}₂Cu] (3 (n = 2), 4 (n = 3)) with the loss of phenylselenato(alkyl)amine and acetic acid. In both these complexes, one arm of the ligand molecule undergoes hydrolysis, and links with Cu(II) in a bidentate (NO) fashion, as confirmed by single crystal X-ray crystallography of complex 3. The selenium atoms do not form part of the copper(II) distorted square planar coordination sphere which has a trans-CuN₂O₂ core. The average Cu–N and Cu–O distances are, respectively, 1.973(3) and 1.898(2) Å. The N–Cu–N and O–Cu–O angles are, respectively, 167.4(11)° and 164.5(12)°. The compounds 1–4 have been characterized by elemental analysis, conductivity measurements, mass spectrometry, IR, electronic, ¹H and ⁷⁷Se{¹H} NMR spectroscopy and cyclic voltammetry. The interaction of complex 3 with calf thymus DNA has been investigated by a spectrophotometric method and cyclic voltammetry.     

3‐Rhoda‐1,2‐diazacyclopentanes: A Series of Novel Metallacycle Complexes Derived From CN Functionalization of Ethylene

Rh‐containing metallacycles, [(TPA)Rh^III(κ²‐(C,N)‐CH₂CH₂(NR)₂‐]Cl; TPA=N,N,N,N‐tris(2‐pyridylmethyl)amine have been accessed through treatment of the Rh^I ethylene complex, [(TPA)Rh(η²‐CH₂CH₂)]Cl ([ 1 ]Cl) with substituted diazenes. We show this methodology to be tolerant of electron‐deficient azo compounds including azo diesters (RCO₂N?NCO₂R; R=Et [ 3 ]Cl, R=iPr [ 4 ]Cl, R=tBu [ 5 ]Cl, and R=Bn [ 6 ]Cl) and a cyclic azo diamide: 4‐phenyl‐1,2,4‐triazole‐3,5‐dione (PTAD), [ 7 ]Cl. The latter complex features two ortho‐fused ring systems and constitutes the first 3‐rhoda‐1,2‐diazabicyclo[3.3.0]octane. Preliminary evidence suggests that these complexes result from N–N coordination followed by insertion of ethylene into a [Rh]?N bond. In terms of reactivity, [ 3 ]Cl and [ 4 ]Cl successfully undergo ring‐opening using p‐toluenesulfonic acid, affording the Rh chlorides, [(TPA)Rh^III(Cl)(κ¹‐(C)‐CH₂CH₂(NCO₂R)(NHCO₂R)]OTs; [ 13 ]OTs and [ 14 ]OTs. Deprotection of [ 5 ]Cl using trifluoroacetic acid was also found to give an ethyl substituted, end‐on coordinated diazene [(TPA)Rh^III(κ²‐(C,N)‐CH₂CH₂(NH)₂‐]⁺ [ 16 ]Cl, a hitherto unreported motif. Treatment of [ 16 ]Cl with acetyl chloride resulted in the bisacetylated adduct [(TPA)Rh^III(κ²‐(C,N)‐CH₂CH₂(NAc)₂‐]⁺, [ 17 ]Cl. Treatment of [ 1 ]Cl with AcN?NAc did not give the Rh?N insertion product, but instead the N,O‐chelated complex [(TPA)Rh^I ( κ²‐(O,N)‐CH₃(CO)(NH)(N?C(CH₃)(OCH?CH₂))]Cl [ 23 ]Cl, presumably through insertion of ethylene into a [Rh]?O bond.     

Kinetics and quantification of the electrophilic reactivities of substituted thiophenes and structure‐reactivity relationships

Second‐order rate constants (k₁) have been measured spectrophotometrically for reactions of 2‐methoxy‐3‐X‐5‐nitrothiophene 1a‐c (X = NO₂, CN, and COCH₃) with secondary cyclic amines (pyrrolidine 2a , piperidine 2b , and morpholine 2 c ) in CH₃CN and 91:9 (v/v) CH₃OH/CH₃CN at 20°C. The experimental data show that the rate constants (k₁) values exhibit good correlation with the parameters of nucphilicity (N) of the amines 2a‐c and are consistent with the Mayr's relationship log k (20°C) = s(E + N). We have shown that the electrophilicity parameters E derived for 1a–c and those reported previously for the thiophenes 1d‐g (X = SO₂CH₃, CO₂CH₃, CONH₂, and H) are linearly related to the pK_a values for their gem‐dimethoxy complexes in methanol. Using this correlation, we successfully evaluated the electrophilicity E values of 12 structurally diverse electrophiles in methanol for the first time. In addition, a satisfactory linear correlation (r² = 0.9726) between the experimental (log k_exp) and the calculated (log k_calcd) values for the σ‐complexation reactions of these 12 electrophiles with methoxide ion in methanol has been observed and discussed.     

Interfacial Behavior of Cysteine between Mild Steel and Sulfuric Acid as Corrosion Inhibitor

Interfacial behavior of cysteine (Cys) between mild steel and sulfuric acid solution as a corrosion inhibitor has been studied with electrochemical AC (alternating current) and DC (direct current) techniques at (25.0±0.1) °C. The AC impedance results were evaluated using equivalent circuits in which a constant phase element (CPE) has been replaced with double layer capacitance (C_dl) to represent the frequency distribution of experimental data. Changes in impedance parameters (charge transfer resistance and double layer capacitance) indicated that cysteine molecules acted by accumulating at the metal/solution interface. The fractional coverage of the metal surface () was determined using AC impedance results and it was found that the adsorption of cysteine on the mild steel surface followed a Langmuir isotherm model with a standard free energy of adsorption (ΔG⁰_ads) of −35.1 kJ·mol⁻¹.To clarify the type of interaction between mild steel surface and cysteine molecules with a molecular orbital approach, electronic properties, such as, the highest occupied molecular orbital (HOMO) energy, the lowest unoccupied molecular orbital (LUMO) energy, and the frontier molecular orbital coefficients have been calculated. Energy gaps for the interaction of mild steel surface and cysteine molecules (E_{LUMO Fe}−E_{HOMO Cys} and E_{LUMO Cys}−E_{HOMO Fe}) were used to determine whether cysteine molecules acted as electron donors or electron acceptors when they interacted with the mild steel surface. The local reactivity was evaluated through the condensed Fukui indices. Theoretical calculations were carried out using the density functional theory (DFT) at B3LYP level with the 6-311++G(d,p) basis set for all atoms by Gaussian 03W program.     

Real-time monitoring of metal deposition and segregation phenomena during preparation of PdCu membranes

The N₂ and H₂ evolution, respectively, were monitored during deposition of Pd and Cu from electroless plating baths to obtain in-process control of the composition during preparation of 3–7 μm thick PdCu membranes on tubular ceramic substrates. Compositions estimated by gas evolution compare favorably to those measured in post-mortem XRD and EDS analyses, mostly differing by not more than 1 at.%. This result suggests that use of gas evolution measurements to enable in-process control of composition to within 1 at.% is feasible. Annealing experiments in an H₂ atmosphere demonstrated that, at 893 K, only 48 h are needed to form a stoichiometrically homogeneous, 9.5 μm thick, face centered cubic (fcc) Pd₆₃Cu₃₇ membrane from sequentially deposited layers; at 723 K, the same transformation requires over 2 weeks. The appearance of transient body centered cubic (bcc) and fcc phases with lower Pd contents signaled compositional segregation in the initial stages of alloy formation at 723 and 773 K and could be a source of persistent stoichiometric heterogeneity particularly in bcc PdCu membranes. The H₂ fluxes of fcc Pd₅₈Cu₄₂ and Pd₇₀Cu₃₀ membranes were J_H2=(1.6±1.1) mol m⁻² s⁻¹ exp[(−24.8±0.4)kJ mol⁻¹/RT] and J_H2=(3.7±0.6) mol m⁻² s⁻¹ exp[(−21.3±1.0)kJ mol⁻¹/RT], respectively, at 100 kPa H₂ pressure difference.     

Diimido‐, Imido(oxo)‐, Dioxo‐ und Imido(alkyliden)‐Halbsandwich‐Verbindungen über selektive Hydrolyse und α—H‐Abstraktion an Organylkomplexen des sechswertigen Molybdäns und Wolframs

Diimido, Imido Oxo, Dioxo, and Imido Alkylidene Halfsandwich Compounds via Selective Hydrolysis and α—H Abstraction in Molybdenum(VI) and Tungsten(VI) Organyl Complexes Organometal imides [(η⁵‐C₅R₅)M(NR′)₂Ph] (M = Mo, W, R = H, Me, R′ = Mes, tBu) 4 — 8 can be prepared by reaction of halfsandwich complexes [(η⁵‐C₅R₅)M(NR′)₂Cl] with phenyl lithium in good yields. Starting from phenyl complexes 4 — 8 as well as from previously described methyl compounds [(η⁵‐C₅Me₅)M(NtBu)₂Me] (M = Mo, W), reactions with aqueous HCl lead to imido(oxo) methyl and phenyl complexes [(η⁵‐C₅Me₅)M(NtBu)(O)(R)] M = Mo, R = Me ( 9 ), Ph ( 10 ); M = W, R = Ph ( 11 ) and dioxo complexes [(η⁵‐C₅Me₅)M(O)₂(CH₃)] M = Mo ( 12 ), M = W ( 13 ). Hydrolysis of organometal imides with conservation of M‐C σ and π bonds is in fact an attractive synthetic alternative for the synthesis of organometal oxides with respect to known strategies based on the oxidative decarbonylation of low valent alkyl CO and NO complexes. In a similar manner, protolysis of [(η⁵‐C₅H₅)W(NtBu)₂(CH₃)] and [(η⁵‐C₅Me₅)Mo(NtBu)₂(CH₃)] by HCl gas leads to [(η⁵‐C₅H₅)W(NtBu)Cl₂(CH₃)] 14 und [(η⁵‐C₅Me₅)Mo(NtBu)Cl₂(CH₃)] 15 with conservation of the M‐C bonds. The inert character of the relatively non‐polar M‐C σ bonds with respect to protolysis offers a strategy for the synthesis of methyl chloro complexes not accessible by partial methylation of [(η⁵‐C₅R₅)M(NR′)Cl₃] with MeLi. As pure substances only trimethyl compounds [(η⁵‐C₅R₅)M(NtBu)(CH₃)₃] 16 ‐ 18 , M = Mo, W, R = H, Me, are isolated. Imido(benzylidene) complexes [(η⁵‐C₅Me₅)M(NtBu)(CHPh)(CH₂Ph)] M = Mo ( 19 ), W ( 20 ) are generated by alkylation of [(η⁵‐C₅Me₅)M(NtBu)Cl₃] with PhCH₂MgCl via α‐H abstraction. Based on nmr data a trend of decreasing donor capability of the ligands [NtBu]^2— > [O]^2— > [CHR]^2— ? 2 [CH₃]^— > 2 [Cl]^— emerges.     

Spectrophotometric studies of the thermodynamics of sitting-atop complexation between free base meso-tetraarylporphyrins and titanium(IV) chloride

Titanium(IV) chloride reacts with free base meso-tetraarylporphyrin and its ortho, meta and para-substituted derivatives (H₂T(X)PP; X: OCH₃, CH₃ and Cl) for formation of sitting-atop (SAT) complexes, [TiCl₄(H₂T(X)PP)]. The computer fitting of the variation of the absorbance versus mole ratio by KINFIT program was used for calculation of the formation constants of these complexes in chloroform. Thermodynamic parameters, ΔG°, ΔH°, ΔS°, have been determined and the influence of the temperature and the substituted aryl groups (electronic and steric effects) in the free base porphyrins on the stability of the SAT complexes was studied.