Jaroslav Podlaha

SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF PD(II) AND PT(II) COMPLEXES WITH P-BONDED 1'-(DIPHENYLPHOSPHINO)FERROCENECARBOXYLIC ACID

Abstract The title hybrid phosphine ligand (Hdpf) coordinates to Pt(II) and Pd(II) as a monodentate phosphine. In the absence of deprotonating agents, its carboxyl group remains uncoordinated to metal, but takes part in various types of hydrogen bonding. Using K2MCl4 as the metal ion source, trans-square planar complexes of the M(Hdpf-P)2X2 type (MPd, XCl, Br; MPt, XCl) were obtained. While Pd(Hdpf-P)2Cl2 is formed also from Pd(cycloocta-1,5-diene)Cl2, the analogous Pt(II)–cod complex provides cis-square planar Pt(Hdpf-P)2Cl2. The trans-chlorides behave inconsistently on recrystallization from carboxylic acids. While acetic acid gives single crystals of the solvates M(Hdpf-P)2Cl2·2 AcOH, propionic or formic acid does not form solvates with Pt(Hdpf-P)2Cl2 at comparable conditions. Single crystal X-ray structure determination of the last four complexes revealed remarkable differences in the conformation of the ferrocenyl moiety and in inter- and intramolecular hydrogen bonding. The two isostructural solvates have molecular arrangement with solvent molecules hydrogen-bonded to the carboxyl groups of the ligand, thus saturating their hydrogen-bond capability. As can be expected, the structure of the unsolvated trans-Pt(Hdpf-P)2Cl2 is that of a one-dimensional polymer linked by intermolecular hydrogen bonds. Finally, the cis-complex is dimeric in the crystal, being joined by pairs of the peripheral carboxyls; there is a further bonding π–π interaction between the phenyl groups of the cis-phosphines.

The stability constant of the UO22+ -humic acid complex

Between pH 3.5 and 7, humic acids form a water-soluble uranyl-humic acid complex with the uranyl ion, UO22+ (log β1 = 7.8 ± 0.4 at μ = 0.1). The stability constant of the complex is practically independent of the ionic strength (μ). Experimental results can be explained by the formation of a complex in which every uranyl ion is simultaneously bonded to one phenolic oxygen and one dissociated carboxyl group. The bonding through the phenolic group is considerably stronger than that through carboxylic groups.

Synthesis, characterization and X-ray structural, electrochemical and Mössbauer study of mercury(II) complexes with 1′-(diphenylphosphino)ferrocenecarboxylic acid

Abstract Reaction of mercury(II) halides with 1′-(diphenylphosphino)ferrocenecarboxylic acid (Hdpf) affords [HgX2(Hdpf-P)2] or [HgX(μ-X)(Hdpf-P)]2 complexes (X=Cl, Br, I) depending on the stoichiometry of the educts. The complexes have been studied by IR, Mossbauer and solution NMR spectroscopy. In dimethyl sulfoxide-d6 solution, 1H- and 31P{1H}-NMR spectra indicate solvolytic cleavage of the mercury(II)–phosphine bond resulting in partial decomplexation of the phosphine ligand. Electrochemical measurements in donor solvents also confirm the presence of a non-coordinated ligand since the electrochemical behavior is the superposition of that of the product of solvolysis and of the ligand. X-ray structural analysis, of the representatives of both types, was carried out: [HgBr2(Hdpf-P)2] ([C46H38Br2Fe2HgO4P2], monoclinic; space group C2/c, a=19.453(1), b=13.704(1), c=17.929(2) A; β=114.953(7)°; Z=4) and [HgBr(μ-Br)(Hdpf-P)]2·2CH3CO2H ([C54H54Br4Fe2Hg2O12P2], triclinic; space group P, a=9.442(1), b=11.7101(9), c=14.806(1) A; α=109.692(7), β=92.494(9), γ=101.883(7)°; Z=1). The P-monodentate coordination of the phosphinocarboxylic ligand was confirmed in both cases, the carboxyl group being involved in hydrogen bonding to carboxyl groups of either neighboring ligand or solvating acetic acid. The expected Br2P2 and Br3P tetrahedral donor sets around Hg(II) are the subject of different degrees of deformation due to steric effects. 57Fe Mossbauer spectra of the complexes also point to the P-coordination of the ferrocenylphosphino ligand, as follows from the decrease of the quadrupole splitting and only a slight variation of the isomer shift on going from ligand to complex.

Metal complexes of thiopolycarboxylic acids. I. Complexes of thiodiacetic acid in solution

Abstract The complexes of thiodiacetic acid with the first transition row metal ions were investigated in the diluted aqueous solution. The 1:1 and 1:2 (metal-to-ligand) complexes are formed with all metals studied with the exception of V 2+ , Mn 2+ , Cr 3+ , and Fe 3+ , where only 1:1 complexes appear to exist. The stability constants, calculated from potentiometric and spectrophotometric data, agree well with the Irving-Williams series. From the electronic spectra of the complexes, the pseudo-octahedral crystal field parameters were calculated and the ligand was placed into the spectrochemical and nephelauxetic series.

Stereocontrolled introduction of an amino group at C-6 of d-galactose via (3,3)-sigmatropic rearrangements—novel synthesis of lincosamine and 7-epi-lincosamine precursors

Abstract A new and stereoselective route to the aminoglycoside components of the antibiotics lincomycin and clindamycin is presented. The key step involves diastereoselective introduction of the amino group at C-6 of d -galactose by (3,3)-sigmatropic rearrangements of the corresponding allylic (Z)-trifluoroacetimidate and (Z)- and (E)-allylic thiocyanates. Epoxidation of the resulting trifluoroacetamide with m-CPBA led to the epoxide with high threo-selectivity.

Metal complexes of thiooycarboxylic acids.II. solid salts and complexes of thiodiacetic acid

Abstract Sokid sodium salts of thiodiacetic acid and its 1:1 and 1:2 (metal-to-ligand) complexes with first transition row metals have been prepared in the solid state. According to the properties of these compounds thiodiacetate ion appears to act as a terdentate ligand forming solid complexes of a pseudo-octahedral symmetry.

Intramolecular transfer of axial to central chirality in the strecker reaction. Synthesis and stereochemistry of 5,7-dicyano-6,7-dihydro-5H-dibenz[c,e]azepines

Abstract The reaction of unsubstituted as well as 6,6′-disubstituted biphenyl-2,2′-dicarboxaldehydes with HCN and ammonia or methylamine has been investigated. It has been found that the final reaction step, the addition of HCN to the intermediary cyclic imino nitriles, is a strictly diastereoselective process, yielding always only one of the two diastereoisomers of the title products, the stereoselection being controlled by the chiral twist of the biaryl axis.

Preparation, resolution and absolute configuration of 2,2′-bipyridine-3,3′-dicarboxylic acid 1,1′-dioxide and its ester

Abstract The title racemic acid (±)- 1 , prepared by hydrogen peroxide oxidation of 2,2′-bipyridine-3,3′-dicarboxylic acid, was resolved via the brucine salts. The absolute configuration of acid (+)- 1 was determined by X-ray diffraction study of its barium salt using the Bijvoets anomalous dispersion method. The activation energy ΔG # for interconversion of enantiomers of the dimethyl ester 2 was found to be −106.5 kJ/mol at 50 °C.

Trigonal bipyramidal penta-aquazinc(II): crystal structure of penta-aquazinc(II) bis(3,3′,3″-phosphinetriyltripropionato)dizincate(II,II) heptahydrate

Crystals of the title compound are hexagonal, space group P61 or P65. The crystal structure was determined by the heavy-atom method from 2 675 unique reflections and refined to R= 0.059. The structure can be best formulated as an ionic polymer with the composition ([Zn(H2O)5][Zn2{P(CH2CH2CO2)3}2]·7H2O)n. It consists of a three-dimensional network of [Zn{P(CH2CH2CO2)3}]– anions, where the zinc atoms are each tetrahedrally co-ordinated by three carboxyl oxygen atoms belonging to three different 3,3′,3″-phosphinetriyltripropionato ligands [Zn–O, 1.950(12)–1.991 (13)A] and by one phosphorus atom from a fourth ligand [Zn–P, 2.405(4) and 2.429(4)A; the first crystallographically documented zinc–phosphine bond]. Zinc cations are located in holes of the network as the hitherto unknown [Zn(H2O)5]2+ moieties with trigonal bipyramidal arrangement. The structure is stabilized by hydrogen bonding in which carboxylate oxygen atoms and both coordinated and lattice water molecules are involved.

Axially chiral dilactams. Synthesis, racemization barriers and crystal structures

Abstract The racemic as well as optically active dilactams 1 and 2 were prepared as the first representatives of axially chiral dilactams possessing a biaryl axis as the sole element of chirality. Their absolute configurations and inversion barriers were determined. The molecular structure and supramolecular self-assembly of the racemic dilactams directed by hydrogen bonding and aryl–aryl stacking was elucidated by single crystal diffraction analysis.