Structure and dynamics of P,N-containing heterocycles and their metal complexes in solution

Conformations and dynamics of 1,5-diaza-3,7-diphosphacyclooctane (1) with chiral l-menthyl substituents on the phosphorus atoms and several metal complexes thereof were investigated by a variety of DNMR methods. In solution 1 adopts a C(2) symmetrical "crown"-like conformation (CW) and the conformational preference and dynamics of the complexes depend on the type of metal: for the Cu complex the CW form is preferred, whereas the Pd, Pt, or Mo complexes exist in an equilibrium of two "chair-boat"-like conformations (CB/CB*). The barriers of interconversion between these two conformations for the Pd and Pt complexes are about 2 times higher than for the Mo complex. Quantum chemical calculations (B3LYP/6-31G(d)) are in agreement with experimental findings.     

Directionality of Dihydrogen Bonds: The Role of Transition Metal Atoms

A theoretical study on two series of electron‐rich group 8 hydrides is carried out to evaluate involvement of the transition metal in dihydrogen bonding. To this end, the structural and electronic parameters are computed at the DFT/B3PW91 level for hydrogen‐bonded adducts of [(PP₃)MH₂] and [Cp*MH(dppe)] (M=Fe, Ru, Os; PP₃=κ⁴‐P(CH₂CH₂PPh₂)₃, dppe= κ²‐Ph₂PCH₂CH₂PPh₂) with CF₃CH₂OH (TFE) as proton donor. The results are compared with those of adduct [Cp₂NbH₃] ? TFE featuring a “pure” dihydrogen bond, and classical hydrogen bonds in pyridine ? TFE and Me₃N ? TFE. Deviation of the H ??? H? A fragment from linearity is shown to originate from the metal participation in dihydrogen bonding. The latter is confirmed by the electronic parameters obtained by NBO and AIM analysis. Considered together, orbital interaction energies and hydrogen bond ellipticity are salient indicators of this effect and allow the MH ??? HA interaction to be described as a bifurcate hydrogen bond. The impact of the M ??? HA interaction is shown to increase on descending the group, and this explains the experimental trends in mechanisms of proton‐transfer reactions via MH ??? HA intermediates. Strengthening of the M ??? H interaction in the case of electron‐rich 5d metal hydrides leads to direct proton transfer to the metal atom.     

Synthesis and biological activity of simplified belactosin C analogues

Successful biochemical studies of the natural products belactosin A and C and their acylated congeners have shown a β-lactonecarboxamide moiety to be a possible core structure of powerful proteasome inhibitors. As a part of further investigations, variously decorated simplified β-lactonecarboxamides have been synthesized in order to understand structure-biological activity relations in detail, to find ways of improving their biological activity and stability and to reduce the complexity of their preparation. Biological tests showed that the best compounds possess a high potential against phytopathogenic fungi in the greenhouse.     

Nanoscale Hemispheres in Novel Mixed-Valent Uranyl Chromate(V,VI), (C(3)NH(10))(10)[(UO(2))(13)(Cr(12)(5+)O(42))(Cr(6+)O(4))(6)(H(2)O)(6)](H(2)O)(6)

The structure of a novel mixed-valent chromium uranyl compound, (C(3)NH(10))(10)[(UO(2))(13)(Cr(12)(5+)O(42))(Cr(6+)O(4))(6)(H(2)O)(6)](H(2)O)(6) (1), obtained by the combination of a hydrothermal method and evaporation from aqueous solutions with isopropylammonium, contains uranyl chromate hemispheres with lateral dimensions of 18.9 × 18.5 ?(2) and a height of about 8 ?. The hemispheres are centered by a UO(8) hexagonal bipyramid surrounded by six dimers of Cr(5+)O(5) square pyramids, UO(7) pentagonal bipyramids, and Cr(6+)O(4) tetrahedra. The hemispheres are linked into two-dimensional layers so that two adjacent hemispheres are oriented in opposite directions relative to the plane of the layer. From a topological point of view, the hemispheres have the formula U(21)Cr(23) and can be considered as derivatives of nanospherical cluster U(26)Cr(36) composed of three-, four-, and five-membered rings.     

Synthesis of porphyrinoids with silane anchors and their covalent self-assembling and metallation on solid surface

We have synthesized a set of porphyrin and phthalocyanine compounds with two different silane anchors. Syntheses of the anchor-substituted chromophores have been carried out via hydrosilylation of alkene derivatives, catalyzed by platinum complexes. The reduction side-process was suppressed using specific anchor/catalyst pairs, and the silane-containing compounds were successfully isolated from hydrogenated by-products in pure form with good yields. The target porphyrinoids having stable reactive silane anchors possess the ability to self-assemble on metal oxides and quartz surfaces and optical fibers. Covalent attachment is done in one-step, which makes the bonding process fast and easy. Immobilized chromophores were further converted by on-surface reactions into Zn(II) and Mg(II) metal complexes. The metallation time was found to be as fast as 1 min for Zn ion. Bonding densities calculated from the absorbances of the deposited layers give rough estimations for packing of the molecules on various substrates and evidence for monomolecular layers formation.     

Coordination chemistry of diphenylphosphinoferrocenylthioethers on cyclooctadiene and norbornadiene rhodium(i) platforms

Complexes [RhCl(diene)(P,SR)] with chiral ferrocenyl phosphine-thioethers ligands (diene = norbornadiene, NBD, 1(R), or 1,5-cyclooctadiene, COD, 3(R); P,SR = CpFe(1,2-η(5)-C(5)H(3)(PPh(2))(CH(2)SR); R = tBu, Ph, Bz, Et) and the corresponding [Rh(diene)(P,SR)][BF(4)] (diene = NBD, 2(R); COD, 4(R)) have been synthesized from [RhCl(diene)](2) and the appropriate P,SR ligand. The molecular structure of the cationic complexes 2(tBu), 4(Ph) and 4(Bz), determined by single-crystal X-ray diffraction, shows the expected slightly distorted square planar geometry. For the neutral chloride complexes, a combination of experimental IR and computational DFT investigations points to an equally four coordinate square planar geometry with the diene ligand, the chlorine and the phosphorus atoms in the coordination sphere and with a dangling thioether function. However, a second isomeric form featuring a 5-coordinated square planar geometry with the thioether function placed in the axial position is easily accessible in some cases.     

Synthesis,IR/Raman,and quantum‐chemical structural analysis of new octathiotetraphosphetane ammonium salts

New octathiotetraphosphetane ammonium salts are obtained based on the reaction of white phosphorus (P₄) and elemental sulfur with aliphatic mercaptans in the presence of amines (morpholine , methylmorpholine, pyrrolidine, and N,N‐dimethylbenzylamine). Both the salts and novel Cu(I) chloride complex with the pyperidinium salt of octathiotetraphosphetane are characterized by IR/Raman spectroscopy in combination with DFT methods. The comparative spectral analysis reveals clear spectral features, characteristic for a P₄S₈⁴⁻ anion, which are present in IR and Raman spectra of all the compounds obtained. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 22:24–30, 2011; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20651     

Green Chemistry. Reaction of Elemental Phosphorus (P4) and Elemental Sulfur with Protonodonor Reagents: New Methods for the Synthesis of Ammonium Salts of S,S′‐Dialkyltetrathiophosphoric Acids and Octathiotetraphosphetane

A new reaction of white phosphorus (P₄) with elemental sulfur and thiols in the presence of different amines has been investigated. Ammonium salts of S,S′‐dialkyltetrathiophosphoric acids have been observed as main products of the reaction. Octathiotetraphosphetane ammonium salts were formed as side products. The reaction is characterized by a complete conversion of the white phosphorus and is not accompanied by the release of hydrogen sulfide. The crystal structures of both products were determined by the single crystal X‐ray diffraction. Biological activity of obtained compounds was investigated, and some promising compounds with antifungal activity identified. © 2013 Wiley Periodicals, Inc. Heteroatom Chem 24:163–167, 2013; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.21077     

Numerical study of stress and plastic strain evolution under compression and shear of a sample in a rotational anvil cell

The large-strain problem on the evolution of distribution of the components of stress tensor and plastic strain in a sample under compression and torsion in a rotational anvil cell was formulated and studied in detail using the FEM. Results are obtained for compression by different axial forces and torsion under two different constant axial forces. The effects of redistribution of the friction radial and torsional stresses and the load on a sample and gasket on the resultant fields are elucidated. Small pressure self-multiplication effect is revealed during torsion after compression below some critical force, and significant heterogeneity of all fields is found. Strong shear strain localization near the contact surface between sample and anvil is quantified. Results are compared with the simplified solution and available experiments. The results obtained are important for the determination of elastic and plastic properties of materials under high pressure and for the interpretation of kinetics of strain-induced phase transformations and chemical reactions.