Hydrierung von weißem Phosphor zu Phosphan mit Rhodium- und Iridiumtrihydriden

Nur eines der vier P-Atome von P4 wird bei der Reaktion mit den Trihydriden [(triphos)MH3] (M = Rh, Ir) zu Phosphan umgesetzt [Gl. (a)]. Das zuruckbleibende cyclo-P3-Fragment wird vom entsprechenden Metallfragment unter Bildung der Komplexe [(triphos)M(η3-P3)] abgefangen. Fur die Hydrierung wird ein Mechanismus vorgeschlagen, bei dem die Komplexe [(triphos)MH(η1:η1-P4)] und [(triphos)M(η1:η2-HP4)] als Zwischenstufen auftreten; die letztgenannten Komplexe enthalten den neuartigen Hydridotetraphosphanliganden HP4−.

Proton coordination by polyamine compounds in aqueous solution

Abstract The present article is concerned with proton transfer reactions in aqueous solution of open-chain, macrocyclic and macropolycyclic or cage compounds having nitrogen atoms as protonation sites in the molecular framework, although several compounds with additional different donors will be considered. The main purpose of this review is to collect some significant examples of proton transfer processes in order to show how the electronic properties and molecular topology of polyamines affect the thermodynamic parameters of their protonation equilibria.

Metal complexes of the carbonic anhydrase inhibitor methazolamide (Hmacm). Crystal structure of the Zn(macm)2 (NH3)2. Anticonvulsant properties of the Cu(macm)2 (NH3)3(H2O)

Complexes of Co(II), Cu(II), and Zn(II) with deprotonated methazolamide and ammonia are synthesized and characterized. The complex Zn(macm)2(NH3)2 crystallizes in the monoclinic C2/c space group with a = 13.468(1), b = 6.759(1), c = 23.014(2) A, beta = 90.27(1), and Z = 4. The structure was refined to R = 0.049 (Rw = 0.053). The Zn(II) ion is coordinated to two deprotonated sulfonamido nitrogen atoms of the macm- ligand and two nitrogen atoms of the ammonia ligands in a distorted tetrahedron. The Zn(macm)2(NH3)2 complex is shown to be a simple model for the methazolamide inhibition of CA. EHMO calculations applied to fractional coordinates of the Zn(macm)2(NH3)2 complex indicate that the at…

Hydrogenation of White Phosphorus to Phosphane with Rhodium and Iridium Trihydrides.

Only one of the four P atoms of P4 reacts with rhodium and iridium trihydrides [(triphos)MH3 ] to provide phosphane [Eq. (a)]. The resulting cyclo-P3 fragment is efficiently scavenged by the metal fragment to give the complexes [(triphos)M(η3 -P3 )]. A mechanism accounting for the hydrogenation reaction is proposed in which the complexes [(triphos)MH(η1 :η1 -P4 )] and [(triphos)M(η1 :η2 -HP4 ] are intermediates. The latter complex contains the unprecedented hydridotetraphosphane ligand HP4- .

Molybdenum(VI)-dioxo complexes with sterically bulky thiocarboxylate ligands. Reactions with aliphatic thiols and electrochemical properties

Abstract Under acid conditions, the reaction of (Bu n 4 N)2[Mo VI O 2 (O 2 CC(S)Ph 2 ) 2 ] with aliphatic thiols yields the monomeric [Mo V O(O 2 CC(S)Ph 2 ) 2 ] − as unique complex product. The experimental pseudo-first order rate constant with respect to the Mo(VI) complex was found to be K =6.1 × 10 −5 s −1 . At neutral pH, however, an unstable Mo(IV) species was formed which was also electrochemically detected in a reversible Mo(V,IV) couple. [Mo V O(O 2 CC(S)Ph 2 ) 2 ] − appears to be obtained by the reaction of [Mo IV O(O 2 CC(S)Ph 2 ) 2 ] 2− with unreacted [Mo VI O 2 (O 2 CC(S)Ph 2 ) 2 ] 2− . Steric features on the ligand (gemdiphenyl groups) explain that the latter reaction does not…

New molecular catalysts for ATP cleavage. Criteria of size complementarity

The interaction of the cyclophane receptor 2,5,8,11,14,17-hexaaza[18]metacyclophane (L) with the nucleotides ATP, ADP and AMP is described. L yields one of the largest rate enhancements for hydrolytic ATP cleavage observed in macrocyclic polyamines. The process is specific for the formation of ADP and involves a high degree of geometrical complementarity between host and guest species. The analogue compound 24-hydroxy-2,5,8,11,14,17-hexaaza[18]metacyclophane (L11) shows also a high degree of ATP activation. However, in this case deprotonation of the hydroxy group results in almost complete quenching of the ATPase activity above pH 7.0.

Cyclic voltammetric analysis of pH-dependent complex formation equilibria in anion coordination chemistry

A procedure to analyze pH-dependent complex formation equilibria from cyclic voltammetry is described. Application to adduct formation equilibria between [Fe(CN)(6)](4-) and [Fe(CN)(6)](3-) with different polyammonium receptors is discussed. Extension to the interaction of substrates such as ATP, NAD(+), NADP(+), and carboxylate ions with these receptors by means of competitive interaction with hexacyanoferrate(II) ion is presented.

Thermodynamic and fluorescence emission studies on chemosensors containing anthracene fluorophores. Crystal structure of {[CuL1Cl]Cl}2·2H2O [L1 = N-(3-aminoprophyl)-N′-3-(anthracen-9-ylmethyl)aminopropylethane-1,2- diamine]

The co-ordination capabilities toward hydrogen ions, Co2+, Ni2+, Cu2+, Zn2+ and Cd2+ of the novel receptor 2,6,9,13-tetraaza[14](9,10)anthracenophane (L) and of its open-chain counterpart N-(3-aminopropyl)-N′-3-(anthracen-9-ylmethyl)aminopropylethane-1,2-diamine (L1) is described. Stepwise protonation constants of the cyclic receptor (L) are lower than those of the open-chain receptor (L1) . Quenching effects of the fluorescence emission occur upon first and second deprotonation of L and upon second deprotonation of L1. Stability constants of the Co2+, Ni2+, Cu2+, Zn2+ and Cd2+ complexes follow the Irving–Williams trend and are intermediate between those of triethylenetetraamine with termin…

Dopamine interaction with a polyamine cryptand of 1H-pyrazole in the absence and in the presence of Cu(ii) ions. Crystal structure of [Cu2(H−1L](ClO4)3·2H2O

The crystal structure of the binuclear Cu2+ complex [Cu2(H−1L)](ClO4)3 ·2H2O of the cryptand L = 1,4,7,8,11,14,17,20,21,24,29,32,33,36-tetradecaazapentacyclo[12.12.12.1 6,9.119,22,1,31,34]hentetraconta-6,9(41), 19(40), 21,31,34(39)-hexaene is presented; evidence for the formation in solution of binary L–dopamine and ternary Cu2+–L–dopamine complexes is presented.

Compounds of tungsten(VI) with citric acid: A spectrophotometric, polarimetric and hydrogen-1, carbon-13 N.M.R. study of the formation and interconversion equilibria in aqueous solution

Tungsten(VI)-citrate complexes, which occur in aqueous solution, were studied by polarimetric and absorbance measurements. The pH of the medium is the principal variable controlling complex formation and interconversion equilibria. At high pH (>6), the stable complexes are monomers with 1∶2 and 1∶1 stoichiometry, depending on the tungsten(VI)-citrate ratio, while at lower pH two different dinuclear complexes are formed. The intervals of existence of these species with the pH, the number of equivalents of acid necessary for their formation, as well as the conditional stability constant, have also been calculated. The structure of these compounds have been investigated by1H and13C-n.m.r. spec…

Effect of Nitrogen Methylation on Cation and Anion Coordination by Hexa- and Heptaazamacrocycles. Catalytic Properties of These Ligands in ATP Dephosphorylation

The stability constants of the complexes formed by 1,10-dimethyl-1,4,7,10,13,16-hexaazacyclooctadecane (L) and 1,4,7-trimethyl-1,4,7,10,13,16,19-heptaazacyclohenicosane (L1) with Ni(2+), Cu(2+), Zn(2+), Cd(2+), and Pb(2+), as well as that for the formation of PbL2(2+) (L2 = 1,4,7,13-tetramethyl-1,4,7,10,13,16-hexaazacyclooctadecane), were determined by means of potentiometric (pH-metric) titrations in 0.15 mol dm(-)(3) NaClO(4) at 298.1 +/- 0.1 K. The enthalpy changes for the formation of Cu(2+) complexes with L and L1 were measured by means of microcalorimetry. These thermodynamic data were compared with those previously reported for L2, 1,4,7,10,13,16-hexaazacyclooctadecane (L3), and 1,4,…

Structural characterization in solution of multifunctional nucleotide coordination systems

The interaction in aqueous solution of the cyclophane receptors 2,6,10,13,17,21-hexaaza[22]orthocyclophane (L11) and 2,6,10,13,17,21-hexaaza[22]paracyclophane (L22) with the nucleotides ATP, ADP and AMP has been studied by pH titration and NMR. The obtained results are compared with those previously reported for the analogous meta-substituted receptor 2,6,10,13,17,21-hexaaza[22]metacyclophane (L). All the experimental data support the actuation of these cyclophane molecules as multi-point binders of nucleotides through electrostatic, hydrogen bonding and π-stacking interactions. The combined use of NMR and molecular dynamics permits us to get a rather reliable picture of the way in which th…

1,4,8,11-Tetrakis(4-ferrocenyl-3-azabutyl)-1,4,8,11-tetraazacyclotetradecane as a ferrocene-functionalised polyammonium receptor for electrochemical anion sensing

The interaction of the ferrocene-functionalised polyaza receptor 1,4,8,11-tetrakis(4-ferrocenyl-3-azabutyl)-1,4,8,11-tetraazacyclotetradecane (L1) with sulfate, phosphate and ATP has been studied potentiometrically in THF–water 70∶30 v/v (0.1 mol dm–3 tetrabutylammonium perchlorate, 25 °C). The molecular structure of the free receptor has been determined by single-crystal X-ray procedures. An electrochemical study on L1 as a function of the pH has been carried out in THF–water 70∶30 v/v in the presence of the sulfate, phosphate and ATP anions. The potential use of L1 as an anion sensing receptor is discussed in terms of the electrochemical and potentiometric data and its behaviour is compar…

Mononuclear mixed oxosulfidomolybdate(VI) complexes with aminodicarboxylic ligands. Synthesis and spectroscopic characterization by multinulcear magnetic resonance spectroscopy

Addition of B2S3 to a methanolic solution of the MoVIO3L2− complex (L=N,N-bis(ethanoic acid)-1-amino-2- methylthio-ethane) results in the formation of two different monomeric oxosulfidomolybdate(VI) complexes, [MoO2SL]2− and [MoOS2L]2− as indicated by 1H, 13C, 17O and 95Mo NMR spectroscopy and by the reaction of these two sulfurated species with triphenylphosphine. The temperature dependences of the 1H NMR spectra indicate exchange processes for both sulfido complexes. Their redox properties are discussed and contrasted with those observed for the parent fac-trioxo molybdenum(VI) complex. The primary synthetic route to mixed oxosulfido [MoO3−nSnL]2− complexes described here can be extended …

Superoxide dismutase activity of ternary copper complexes of sulfathiazole and imidazole derivatives. Synthesis and properties of [CuL2(R-Him)2] [HL=4-amino-N-(thiazol-2-yl)benzenesulfonamide, R-Him=4-methylimidazole, 4,4-dimethylimidazoline or 1,2-dimethylimidazole]. Crystal structure of [CuL2(4,4-dimethylimidazoline)2]

Abstract New ternary copper(II) complexes of sulfathiazole (4-amino-N-(thiazol-2-yl)benzenesulfonamide)(HL) and methyl imidazole derivatives have been synthesised and characterised. The crystal structure of the complex [CuL2(4,4-dmHim)2] (1) [4,4-dmHim=4,4-dimethylimidazoline] has been determined. The copper centre has a quasi regular square planar environment with Cu-nitrogen bond lengths ranging from 1.952 to 2.010 A. From the spectroscopic properties of the complexes [CuL2(1,2-dmHim)2] (2) [1,2-dmHim=1,2-dimethylimidazole] and [CuL2(4-mHim)2] (3) [4-mHim=4-methylimidazole] a distorted tetragonal octahedral geometry is deduced. The compounds showed SOD mimetic activity in fact, a low conc…

New strategies in the development of polynuclear complexes. Crystal structure of the tetranuclear copper(II) complex [Cu4(L1)2(OH)4Cl2(H2O)2]2(H3O2)(ClO4)2Cl·2H2O (L1=2,5,8,11-tetraaza[12](1,4)naphthalenecyclophane)

Abstract The preparation and interaction of the new polyaza[n]naphthalenophanes 2,5,8,11-tetraaza[12](1,4)naphthalenophane (L1) and 2,6,9,13-tetraaza[14](1,4)naphthalenophane (L2) with hydrogen ions and Cu2+ is described. The crystal structure of the new tetranuclear copper(II) complex [Cu4(L1)2(OH)4Cl2(H2O)2]2(H3O2)(ClO4)2Cl·2H2O (L1=2,5,8,11-tetraaza[12](1,4)naphthalenophane) is presented and discussed. A variety of intra- and intermolecular forces contribute to the particular organisation of the crystal. The solution studies indicate the formation of similar tetranuclear species for L1 while for L2 just mononuclear 1:1 species are detected.

Small Azaparacyclophanes as Potential Selective Scavengers of Mercury. Crystal Structure of the Complex Hg2(L1)Cl4 (L1 = 16,17,19,20-Tetramethyl-2,6,9,13-tetraaza[14]paracyclophane)

CO2fixation and activation by metal complexes of small polyazacyclophanes

The interaction of the cyclophanes 2,6,9,13-tetraaza[14]paracyclophane (L1) and 2,6,9,13-tetraaza[14]metacyclophane (L2) and of their Zn2+ and Cu2+ complexes with CO32− and its protonated forms is described. The actuation of the Cu2+–L2 system as an electrocatalyst for the reduction of CO2 to CO in water is advanced. Copyright © 2001 John Wiley & Sons, Ltd.

Interaction of methylmercury(II) with the bifunctional ligand o-diphenylphosphinobenzoate, dpb. Synthesis and characterization of [(dpb)HgMe] and [(dpbo)HgMe], dpbo=o-diphenylphosphinoxidebenzoate

Abstract The complex [(dpb)HgMe] (1) is obtained by reaction of MeHg(OH) with o-diphenylphosphinobenzoic acid (Hdpb); alternatively the solvate [(dpb)HgMe] · 0.5H2O · 0.5C5H5N (1bis) can be prepared by reacting MeHgCl with Hdpb and pyridine. The derivative [(dpbo)HgMe] (2), where dpbo is o-diphenylphosphinoxidebenzoate, is formed by reaction of 1 or 1bis solutions with atmospheric oxygen. Crystal data for 1bis: monoclinic, space group P2/n, a=10.413(4), b=9.831(3), c=20.674(3) A, β=102.51(3)°, Z=2. Crystal data for 2: triclinic, space group P1, a=11.535(2), b=12.897(5), c=13.275(7) A, α=88.31(4), β=73.65(4), γ=85.27(4)°, Z=2. In 1bis the mercury atom displays a distorted linear fashion, bei…

Tungsten-mannitol and sorbitol complexes: Structural characterization by IR and carbon-13 nuclear magnetic resonance spectroscopy

Abstract Polarimetric and spectrophotometric studies of the mannitol-tungsten(IV) system show the formation of three table complexes. Their stoichiometries, degrees of condensation and interconversion equilibria have been studied. The structure of these compounds has been investigated by 13C NMR spectroscopy in aqueous solution and by IR spectroscopy in the solid state for the two species stable at pH

ChemInform Abstract: Proton Coordination by Polyamine Compounds in Aqueous Solution

Abstract The present article is concerned with proton transfer reactions in aqueous solution of open-chain, macrocyclic and macropolycyclic or cage compounds having nitrogen atoms as protonation sites in the molecular framework, although several compounds with additional different donors will be considered. The main purpose of this review is to collect some significant examples of proton transfer processes in order to show how the electronic properties and molecular topology of polyamines affect the thermodynamic parameters of their protonation equilibria.

Preparation of 4-substituted 1,3-oxathiolan-5-onesviathe sulphenium ion intermediate generated by the pummerer rearrangement

4-Substituted 1,3-oxathiolan-5-ones have been synthesized via the Pummerer rearrangement from the S-oxide of the parent molecule. The 4,5-dione is obtained in the presence of pyridine N-oxide.

Tungsten(VI)-gluconic acid complexes: Polarimetric and13C-N.m.r. Studies in an excess of tungsten(VI)

A polarimetric study of the tungsten (VI)-gluconic acid system in an excess of metal reveals the formation of four stable complexes: two monomers with 1 : 2 and 2: 1 stoichiometries and two dimers of 2:2 composition. The pH ranges of these species, the amount of acid equivalents their formation requires, and their conditional stability constants have also been calculated.