Reactivity of diacetylplatinum(II) complexes: oxidative addition of alkyl halides and crystal structures of acetyl platinum(IV) complexes

Diacetylplatinum(II) complexes [Pt(COMe)₂(N^N)] (N^N = bpy, 3a; 4,4′-t-Bu₂-bpy, 3b) were found to undergo oxidative addition reactions with organyl halides. The reaction of 3a with methyl iodide and propargyl bromide led to the formation of the cis addition products (OC-6-34)-[Pt(COMe)₂(R)X(bpy)] (R = Me, X = I, 4a; CH₂C≡CH, X = Br, 4k). Analogous reactions of 3a with ethyl iodide, benzyl bromide, and substituted benzyl bromides, 3-(bromomethyl)pyridine, 2-(bromomethyl)thiophene, allyl bromide, and cyclohex-2-enyl bromide led to exclusive formation of the trans addition products (OC-6-43)-[Pt(COMe)₂(R)X(bpy)] (X = I, R = Et, 4b; X = Br, R = CH₂C₆H₅, 4c; CH₂C₆H₄(o-Br), 4d; CH₂C₆H₄(p-COOH), 4e; CH₂-3-py (3-pyridylmethyl), 4f; CH₂-2-tp (2-thiophenylmethyl), 4g; CH₂CH=CH₂, 4h; c-hex-2-enyl (cyclohex-2-enyl), 4i). All complexes 4 were characterized by microanalysis, ¹H and ¹³C NMR and IR spectroscopy. Additionally, complexes 4a, 4f, and 4g were characterized by single-crystal X-ray diffraction analyses. Reactions of 3a and 3b with o-, m- and p-bis(bromomethyl)benzene, respectively, led to the formation of dinuclear platinum(IV) complexes [{Pt(COMe)₂Br(N^N)}₂-{μ-(CH₂)₂C₆H₄}] (5). These complexes were characterized by microanalysis, IR spectroscopy, and depending on their solubility by ¹H and ¹³C NMR spectroscopy, too. A single-crystal X-ray diffraction analysis of complex [{Pt(COMe)₂Br(bpy)}₂{μ-m-(CH₂)₂C₆H₄}] (5b) confirmed its dinuclear composition. The solid-state structures of 4a, 4f, 4g, and 5b are discussed in terms of C–H···O and O–H···O hydrogen bonds as well as π–π stacking between aromatic rings.     

Kinetics and mechanism of the chromium(III)–picolinato chelate ring opening in some chromium(III)–oxalato–picolinato complexes in acidic aqueous solutions

Two Cr^III–picolinato complexes were obtained and characterized in solution. The [Cr(C₂O₄)(pyac)₂]^– and [Cr(C₂O₄)₂(pyac)]^2– ions (pyac = picolinic acid anion) in acidic solutions undergo a reversible one-end Cr^III–picolinato chelate ring opening via Cr^III—N bond breaking. The reaction rate was determined spectrophotometrically in the 0.1–1.0 M HClO₄ range at I = 1.0 M. The observed pseudo-first order rate constant depends on [H⁺] according to the equation: k _obs = a + b[H⁺] + c/[H⁺]. A reaction mechanism, which assumes participation of the protonated and unprotonated forms of the reactants, has been proposed. The kinetic parameters a, b, c have been defined as a = k ₁, b = k ₂ Q ₁, c = k _–1/Q ₂, where k ₁, k _–1,k ₂ are rate constants for the forward and reverse processes and Q ₁, Q ₂ are the protolytic equilibrium constants in the term of the proposed mechanism. The activation parameters have been determined and discussed.     

Quasielastic light scattering study of chemically crosslinked gelatin solutions and gels

Quasielastic light scattering measurements are reported for experiments performed on mixtures of gelatin and glutaraldehyde (GA) in the aqueous phase, where the gelatin concentration was fixed at 5 (w/v) and the GA concentration was varied from 1×10⁻⁵ to 1×10⁻³ (w/v). The dynamic structure factor, S(q,t), was deduced from the measured intensity autocorrelation function, g ₂(τ), with appropriate allowance for heterodyning detection in the gel phase. The S(q,t) data could be fitted to S(q,t)=Aexp(−D _f q ² t)+Bexp(−t/τ_c)^β, both in the sol (50 and 60 ^∘C) and gel states (25 and 40 ^∘C). The fast-mode diffusion coefficient, D _f showed almost negligible dependence on the concentration of the crosslinker GA; however, the resultant mesh size, ξ, of the crosslinked network exhibited strong temperature dependence, ξ∼(0.5−χ)^1/5exp(−A/RT) implying shrinkage of the network as the gel phase was approached. The slow-mode relaxation was characterized by the stretched exponential factor exp(−t/τ_c)^β. β was found to be independent of GA concentration but strongly dependent on the temperature as β=β₀+β₁ T+β₂ T ². The slow-mode relaxation time, τ_c, exhibited a maximum GA concentration dependence in the gel phase and at a given temperature we found τ_c(c)=τ₀+τ₁ c+τ₂ c ². Our results agree with the predictions of the Zimm model in the gel case but differ significantly for the sol state. Received: 25 May 1999 /Accepted in revised form: 27 July 1999     

The crystal and molecular structure of 2-methyl-2,5-diaza-3,4-benzotricyclo[4.3.3.01,5]dodecan-6-ol

The title compound was synthesized by the reaction of cyclooctane-1,5-dione and N-methyl-phenylenediamine in ethanol solution and an X-ray analysis has been carried out. The crystals belong to the monoclinic space groupC2/c, witha=20.032(4) å,b=7.936(1) å,c=17.316(2) å,b=109.73(2),V=2591.2(7) å,Z=8, and D_calc=1.253 M g^–3. The final discrepancy factor isR=0.039 for 866 observed reflections. The analysis showed the synchronous formation of a heterobicyclo[3.3.1]nonane skeleton, and the five-membered ring of the benzoimidazoline presents an envelope conformation flapping at C1.     

Synthesis and spectral properties of substituted 4-chlorooxazoloquinolines

Summary The treatment of a mixture of linearly and angularly annelated 2-substituted oxazolo[4,5-f]quinolones (5a–c) and oxazolo[5,4-g]quinolones (6a–c) and similarly the treatment of 2-substituted oxazolo[5,4-f]quinolones (7a–c) and oxazolo[4,5-g]quinolones (8b,c) with POCl₃ afforded substituted 4-chlorooxazolo[4,5-f]quinolines (9a–c) and 2-substituted 4-chlorooxazolo[5,4-f]quinolines (10b,c), respectively. Spectral characteristics of the synthesized derivatives (¹H and¹³C NMR, IR, UV, and MS) are discussed.Dedicated to Prof.Fritz Sauter on the occasion of his 65th birthday     

Lithium and sodium cation binding of cyclopentadienyl anions: Electronic effects of cyclopentadienyl substitution

The Li⁺ and Na⁺ binding of substituted cyclopentadienyl (Cp) anions were investigated using computational techniques. The ring centroid-metal distances and the binding energies of the Cp-metal complexes correlate very well with the ∑σ_m of the substituted Cp ring. These properties also correlate well with the Cp Θ_zz values. The trend in the correlations is the more electron-rich the Cp (negative ∑σ_m and Θ_zz values values), the shorter the Cp-metal bond and the stronger the binding energy. The NBO metal charges correlate, though not very well in either case, with the Cp Θ_zz and ∑σ_m values. However, there is a substantial increase in correlation when the sum of the absolute value of the Hammett σ_m (∑|σ_m|) is employed. The significantly improved correlation when the ∑|σ_m| values are employed leads us to propose a model for substituted Cp charge transfer upon Li⁺ or Na⁺ complexation, and it also informs us that the Hammett substituent constant σ_m contains information about substituent polarizabilities, at least in the case of Li⁺- and Na⁺-substituted Cp anions.     

Syntheses and characterization of Co(pydc)(H2O)2 and Ni(pydc)(H2O) (pydc = 3,5-pyridinedicarboxylate)

The hydrothermal reaction of 3,5-pyridinedicarboxylic acid (pydcH₂) and Co(NO₃)₂ or Ni(NO₃)₂ in the presence of 4,4′-bipyridine results in two novel compounds Co(pydc)(H₂O)₂ (1) and Ni(pydc)(H₂O) (2). Crystal data: 1, monoclinic, C2/c, a=9.900(2), b=11.984(2), c=7.3748(15) Å, β=105.37(3)°, V=843.7(3) Å³, Z=4; 2, monoclinic, P2₁/c, a=7.7496(6), b=15.0496(11), c=6.4224(5) Å, β=108.437(1)°, V=710.59(9) Å³, Z=4. The structure of 1 is composed of honeycomb layers built up from {CoO₄N} trigonal bipyramids and 3,5-pyridinedicarboxylate bridges. The structure of 2 adopts a three-dimensional framework structure in which the Ni atoms are coordinated by the pydc bridges both within the honeycomb layer and between the layers. The magnetic properties of 1 and 2 have been investigated.     

Coordination chemistry of alkali and alkaline earth cations: Synthesis and crystal structure of potassium(benzo-15-crown-5)2 [3,5-dinitrobenzoate(3,5-dinitrobenzoic acid)2]

The interaction of K(35-Dnb) (35-Dnb=3,5-dinitrobenzoate) with benzo-15-crown-5 (B15C5) in ethanol yields a charge-separated sandwich structured complex [K(B15C5)₂]⁺[35-Dnb(35-DnbH)₂]^– even when equimolar amounts of reactants were used and no external 35-DnbH was added to the reaction mixture. The complex (KC₄₉H₅₁O₂₈N₆, FW=1211.1), is monoclinic,P2₁/c,a=11.063(2),b=10.680(1),c=46.548(8) Å, =91.629(2)⁰,Z=4,D ₀=1.485 g/cm³,D _c=1.468 g/cm³, CuK =1.5418 Å, =17.01 cm^–1, 2<130⁰,F(000)=2520,T=298 K. FinalR for the 6618 observed reflections was 0.071. In the sandwich moiety, the K⁺ is 10-coordinated through all the oxygens of the crown molecules (K⁺–O, 2.76–3.11 Å). The 35-Dnb anion lies 5.3 Å below the lower crown mean plane and is charge separated with respect to K⁺ (K⁺–O^–>7 Å) but undergoes strong hydrogen bonding (2.59 and 2.49 Å) through each carboxylate oxygen with the carboxylic protons of two separate 35-DnbH molecules. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82014 (52 pages).     

Untersuchungen über Chinone, 9. Mitt. Über Acetylderivate vonp-Indazolchinonen

Summary Acetylation of the indazolquinones1a (6-anilino-),b (6-p-toluidino-),c (6-N-methylanilino-),g (6- or 5-methylthio-), andk (benz[f]-) by heating with acetic anhydride yields the 2-acetylindazolquinones4a, b, c, g, andk. Reductive acetylation of the quinones1c, g, h/h ₁(6/5-methyl),k and — for structure elucidation — their 1-N- (2c) and 2-N- (3c, 3e)-methyl derivatives with acetic anhydride, zink powder, and sodium acetate gives the 1-acetyl-(7c, g, h/h ₁,k), resp. 1-methyl- (8c), and 2-methyl- (9c, e) diacetoxyindazoles. In case of1k, two diacetyl derivatives were isolated in addition to the already known triacetyl derivative7k, regardless of the conditions chosen. Acetylation of the intermediate product of the reaction from phenylthio-benzoquinone with diazomethane also yields a triacetyl-hydroquinone (7f). UV/Vis, IR, and¹H NMR spectroscopy were used for structure determination. Comparison of the UV/Vis spectra of the acetyl derivatives4 with those of1, 2, 3, and of compounds7 with those of analog substituted indazols shows that the acetyl group is located in position 2 with compounds4 and in position 1 with compounds7. By means of¹H NMR spectra the position of the acetyl group can be determined by the effect of the carbonyl group on the proton in position3.

     

Kinetics and Mechanism of Chromium(III)-Picolinato and Chromium(III)-Dipicolinato Complexes Aquation in HNO3 Solutions

The acid-catalyzed aquation of [Cr(pic)(H₂O)₄]₂ ²⁺ and [Cr(dpic)(H₂O)₃]⁺(pic = picolinic acid anion, dpic = dipicolinic acid dianion) in nitrate(V) media was studied. The reaction is reversible in the case of the pic-complex and practically irreversible in the case of the dpic-complex. It is assumed that the reactive form of the substrate undergoes fast chelate ring-opening followed by protolytic equilibria, followed by the rate of the Cr—O bond breaking of the monodentate bonded ligand which is the rate-determining step. The kinetics of pic/dpic ligand liberation were followed spectrophotometrically in the 0.4–2.0 M HNO₃ range at I= 2.0 M. The following dependences of the pseudo-first order rate constants on [H⁺] have been established:k _obs=a+b[H⁺](where b and a are apparent rate constants for the forward and the reverse reaction of the pic-complex) and k _obs=b[H⁺]+c[H⁺]²(where b and c are apparent rate constants for the dpic liberation). Fast protolytic pre-equilibria, leading to protonation of the carboxylic oxygen atom on the monodentate bonded ligand, preceeds ligand liberation.     

Self-assembly of two novel bisupporting Keggin-polyoxometalate derivatives: Hydrothermal synthesis and structure characterization of (X = P, m = 1; X = Si, m = 2)

Two novel organic–inorganic hybrid polyoxometalates, (X = P, m = 1 1; X = Si, m = 2 2; 2,2′-bpy = 2,2′-bpyridine), have been synthesized under hydrothermal conditions and structurally characterized by single-crystal X-ray diffraction. They are isostructural, possessing orthorhombic, and the parameters of unit cells for compound 1 are space group Pbca, a = 17.317(4) Å, b = 17.092(3) Å, c = 20.587(4) Å, V = 6445(2) Å³, Z = 4; for compound 2 are space group Pcab, a = 17.181(3) Å, b = 18.198(4) Å, c = 20.672(4) Å, V = 6463(2) Å³, Z = 4. The two compounds show a layer framework constructed from Keggin-polyoxoanion clusters and [Cu (2, 2′-bpy)₂]²⁺ coordination polymer fragments via weak covalent interactions, resulting in a 3D network via supramolecular interactions. Their electrochemical properties are studied in detail.     

The stereoselective thermal rearrangement of chiral lophine peroxides

The thermal reaction of chiral 2-phenyl-4-(p-X-phenyl)-5-(p-Y-phenyl)-4-tert-butyldimethylsilylperoxy-4H-isoimidazoles (5b: X = CF₃, Y = OMe; 5c: X = CF₃, Y = F) was carried out in DMSO. The chiral 2-phenyl-5-(p-X-phenyl)-5-(p-Y-phenyl)-5H-imidazol-4-ones (4b: X = CF₃, Y = OMe; 4c: X = CF₃, Y = F) were quantitatively obtained in 50-60% enantiomer excess (ee). The mechanism for the reaction was proved to be stereoselective 1,5-phenyl migration. Although the sigmatropic 1,5-phenyl migration should be thermally allowed according to the Woodward-Hoffmann rule, the migration actually includes a stepwise process.     

[{(NiOH)2Mo10O36(PO4)Ti2}n]: a novel chainlike trimetal heteropolyanion based on pseudo-keggin fragments

A new mixed Mo/Ni/Ti heteropoly compound [C₅H₅NH]₅ [(NiOH)₂Mo₁₀O₃₆(PO₄)Ti₂] has been hydrothermally synthesized and structurally determined by the single-crystal X-ray diffraction. Black prismatic crystals crystallize in the monoclinic system, space group P2(1)/n, a=11.2075(2), b=37.8328(5) c=13.0888(1) Å, β=101.4580(10)°, M=2276.13, V=5439.19(13) ų, Z=4. Data were collected on a Siemens SMART CCD diffractometer at 293(2) K in the range of 1.68<θ<25.09° using the ω-scan technique (λ=0.71073 Å R(F)=0.0872 for 9621 reflections). The title compound contains a trimetal heteropolyanion polymer and “trans-titanium”-bridging pseudo-Keggin fragments linked to a chain.     

Titanocene-based group-11 metal ions; solid-state structure of {[(η-C5H4SiMe3)2Ti(CCPh)2]2Ag}NO3

The reaction of [Ti](CCR)₂ {[Ti] = (η⁵-C₅H₄SiMe₃)₂Ti; 1a, R = Fc, Fc = (η⁵-C₅H₄)Fe(η⁵-C₅H₅); 1b, R = Ph} with MX {2a, MX = [Cu(NCCH₃)₄]BF₄; M = Ag; 2b, X = ClO₄; 2c, X = NO₃} in a 2:1 molar ratio produces the trinuclear heterobimetallic (Ti₂M) or heptanuclear heterotrimetallic (Ti₂MFe₄) complexes [{[Ti](μ-σ,π-CCR)₂}₂M]X (R = Fc: 3a, M = Cu, X = BF₄; 3b, M = Ag, X = ClO₄. R = Ph: 3c, M = Cu, X = BF₄; 3d, M = Ag, X = ClO₄: 3e, M = Ag, X = NO₃) in high yield. Complexes 3c-3e are also accessible, when {[Ti](μ-σ,π-CCPh)₂}MX (M = Cu: 4a, X = FBF₃; M = Ag: 4b, X = OClO₃; 4c, X = ONO₂) is reacted with one equivalent of 1b. Transferring this reaction scheme to [Ti](CCSiMe₃)₂ (1c) only the formation of the heterobimetallic tweezer complex {[Ti](μ-σ,π-CCSiMe₃)₂}MX {4d, MX = [Cu(NCCH₃)]BF₄; 4e, MX = AgOClO₃} is observed which is attributed to the bulkiness of the acetylide-bound Me₃Si group. The solid-state structure of 3e is reported. In 3e, two [Ti](CCPh)₂ tweezer moieties are chelate-bound by their carbon-carbon triple bonds to a silver(I) ion, resulting in a pseudo-tetrahedral environment at the group-11 metal. is acting as counter-ion to cationic [{[Ti](CCPh)₂}₂Ag]⁺.Additionally, the result of cyclic voltammetric studies on [{[Ti](μ-σ,π-CCPh)₂}₂Cu]BF₄ (3c) is reported.     

Crystal Structure and Thermal Decomposition of 5-Aminotetrazole Trinitrophloroglucinolate

5-Aminotetrazole trinitrophloroglucinolate ((ATZ)TNPG) was prepared and characterized by elemental analysis and FT-IR spectroscopy. The crystal structure was determined by X-ray diffraction analysis and it belonged to orthorhombic system and Pbca space group with a=0.6624(2) nm, b=1.7933(4) nm, c=2.3117(5) nm, V=2.7458(9) nm³, Z=4, and D_c=1.849 g·cm⁻³. The molecular formula was confirmed to be (ATZ)TNPG·2H₂O. 5-Aminotetrazole cation (ATZ⁺) and trinitrophloroglucinol anion (TNPG⁻) were linked into 2-D layers along b-axis and c-axis by hydrogen bonds. Then the layers were linked along a-axis by hydrogen bonds between the water molecules belonging to different layers. The thermal decomposition mechanism of the compound was studied by differential scanning calorimetry (DSC), thermogravimetry-thermogravimetric analysis (TG-DTG), and Fourier transform-infrared (FT-IR) spectroscopy techniques. Under nitrogen atmosphere with a heating rate of 10 °C·min⁻¹, the compound experienced one endothermic process with peak temperature of 76 °C and one exothermal process with peak temperature of 203 °C. The former was confirmed to be a dehydrate process. The latter was the decomposition of TNPG⁻ and ATZ⁺ in the compound. The exothermic enthalpy change of this process was −212.10 kJ·mol⁻¹. The kinetic parameter calculation from Kissinger's method were, E=132.1 kJ·mol⁻¹, ln(A/s⁻¹)=12.54 with r=0.9990, and the calculation results from Ozawa-Doyle's method were, E=133.1 kJ·mol⁻¹ with r=0.9992.     

Tetrameric O–HO hydrogen-bond systems accompanied by C–HO hydrogen-bonds in the crystal of 1,4-bis(hydroxymethyl)triptycene: an X-ray study

The crystal structure of the title compound was determined (crystal data at 143 K: triclinic, space group P−1, Z=4, a=9.538(2) Å, b=11.638(2) Å, c=14.473(2) Å, α=88.647(3)°, β=89.875(3)°, γ=83.835(3)°, V=1596.9(4) ų). In the crystal there exist two kinds of tetrameric O–HO hydrogen-bond (H-bond) systems that are quite similar to each other. The oxygen atoms accept also intermolecular C–HO H-bonds. The two types of the H-bonds connect the molecules to an infinite two-dimensional supramolecular unit, the stacking of which is aided by an intermolecular C–Hπ H-bond. A phase transition with ΔH_t=4.4±0.1 kJ/mol was found at around 420 K.     

Preparation, crystal structure, vibrational spectra and thermal behavior of selenites of ethylene diamine, 1,3-propylene diamine and 1,4-butylene diamine

Selenites of ethylene diamine, propylene diamine and butylene diamine were prepared by crystallization from aqueous solution. The crystal structure was solved for all the substances. Ethylene diammonium(2+) selenite crystallizes in the orthorhombic space group P2₁2₁2, a=11.3710(2) Å, b=11.4390(5) Å, c= 4.6290(4) Å, V= 602.11(6) ų, Z=4, R=0.0341 for 5729 observed reflections. 1,3-Propylene diammonium(2+) selenite dihydrate crystallizes in the monoclinic space group C2/c, a=16.241(14) Å, b=6.673(5) Å, c=17.731(14) Å, β=110.88(2)°, V=1795(3) ų, Z=8, R=0.0271 for 12,233 observed reflections. 1,4-Butylene diammonium(2+) selenite dihydrate crystallizes in the monoclinic space group P2₁/c, a=6.686(5) Å, b=16.597(14) Å, c=9.282(8) Å, β=96.653(14)°, V=1023.2(14) ų, Z=4, R=0.0465 for 2918 observed reflections. The FTIR an FT Raman spectra of all the compounds were recorded and interpreted. The thermoanalytical properties were studied by the TG, DTG, and DTA methods in the 293–633 K temperature range. DSC measurements were carried out in the range from 98 K to the temperature of decomposition of the compounds. No thermal effect indicating a phase transition was observed in this temperature region.     

Establishment of The Power—Time Curve Equation of Bacterial Growth in the Log Phase

The power-time curves of two species of bacteria, Vibro metschnikovii, Vibro bollisae were determined calorimetrically by using a 2277 bioactivity monitor. The power-time curve equation of bacterial growth in the log phase can be expressed as

Extending bond orbital-connection matrix method to the QSPR study of alkylbenzenes: Some thermochemical properties

The properties of alkylbenzenes were estimated, using the contributions of the σ bonds, the conjugated π bond and the steric effect in alkylbenzene molecule. And a novel bond orbital-connection matrix, conjugated π bond orbital-connection matrix in aromatic molecules, was proposed. The eigenvalues of the conjugated π bond orbital-connection matrix can well express the contribution of the conjugated π bond to the properties of aromatic molecules. Using this eigenvalue together with the parameters proposed in our early works, the bond orbital-connection matrix method was extended successfully to the QSPR studies of alkylbenzenes and a general model was obtained to evaluate the thermochemical properties of alkylbenzenes, that is,

p_{(alkylbenzene)}=aN_C–C+b∑X_1CC+cN_C–H+d∑X_1CH+eS_Z/E+k∑X_1π,

Synthesis, structure characterization and fluorescence property of a new fluoride borate crystal, CdZn2KB2O6F

A new fluoride borate crystal, CdZn₂KB₂O₆F, has been synthesized by flux-supported solid-state reaction. The crystal structure has been determined by single-crystal X-ray diffraction. It crystallizes in the trigonal space group with a=5.0381(6) Å, b=5.0381(6) Å, c=15.1550(19) Å, α=90.00°, β=90.00°, γ=120.00°, Z=2. The crystal represents a new structure type in which ZnBO₃ layers are connected through bridging fluorine and cadmium atoms alternately along the c-axis. K⁺ cations are filled in the intralayer open channels to balance charge. IR and Raman spectra further confirm the crystal structure. Photoluminescent measurement reveals that CdZn₂KB₂O₆F exhibits blue fluorescence at room temperature in the solid-state.