Coordination polymers based on [Cp*Fe(η5-P5)]: solid-state structure and MAS NMR studies

Slow diffusion reactions of the pentaphosphaferrocene [Cp*Fe(η(5)-P(5))] (Cp*=η(5)-C(5)Me(5) (1)) with CuX (X=Cl, Br, I) in different stoichiometric ratios and solvent mixtures result in the formation of one- and two-dimensional polymeric compounds 2-6 with molecular formula [{Cu(μ-X)}{Cp*Fe(μ(3),η(5):η(1):η(1)-P(5))}](n) (X=Cl (2a), I (2'c)), [{Cu(μ-I)}{Cp*Fe(μ(3),η(5):η(1):η(1)-P(5))}](n) (3), [{CuX}{Cp*Fe(μ(4),η(5):η(1):η(1):η(1)-P(5))}](n) (X=Cl (4a), Br (4b), I (4c), Br (4'b), I (4'c)), [{Cu(3)(μ-I)(2)(μ(3)-I)}{Cp*Fe(μ(5),η(5):η(1):η(1):η(1):η(1)-P(5))}](n) (5) and [{Cu(4)(μ-X)(4)(CH(3)CN)}{Cp*Fe(μ(7),η(5):η(2):η(1):η(1):η(1):η(1):η(1)-P(5))}](n) (X=Cl (6a), Br (6b)), respectively. The polymeric compounds have been characterised by single-crystal X-ray diffraction analyses and, for selected examples, by magic angle spinning (MAS) NMR spectroscopy. The solid-state structures demonstrate the versatile coordination modes of the cyclo-P(5) ligand of 1, extending from two to five coordinating phosphorus atoms in either σ or σ-and-π fashion. In compounds 2a, 2'c and 3, two phosphorus atoms of 1 coordinate to copper atoms in a 1,2 coordination mode (2a, 2'c) and an unprecedented 1,3 coordination mode (3) to form one-dimensional polymers. Compounds 4a-c, 4'b, 4'c and 5 represent two-dimensional coordination polymers. In compounds 4, three phosphorus atoms coordinate to copper atoms in a 1,2,4 coordination mode, whereas in 5 the cyclo-P(5) ligand binds in an unprecedented 1,2,3,4 coordination mode. The crystal structures of 6a,b display a tilted tube, in which all P atoms of the cyclo-P(5) ligand are coordinated to copper atoms in σ- and π-bonding modes.     

Reaction behaviour of dinuclear copper(I) complexes with m-xylyl-based ligands towards dioxygen

Intramolecular ligand hydroxylation was observed during the reactions of dioxygen with the dicopper(I) complexes of the ligands L(1)(L(1)=alpha,alpha'-bis[(2-pyridylethyl)amino]-m-xylene) and L(3)(L(3)=alpha, alpha'-bis[N-(2-pyridylethyl)-N-(2-pyridylmethyl)amino]-m-xylene). The dinuclear copper(I) complex [Cu(2)L(3)](ClO(4))(2) and the dicopper(II) complex [Cu(2)(L(1)-O)(OH)(ClO(4))]ClO(4) were characterized by single-crystal X-ray structure analysis. Furthermore, phenolate-bridged complexes were synthesized with the ligand L(2)-OH (structurally characterized [Cu(2)(L(2)-O)Cl(3)] with L(2)=alpha, alpha'-bis[N-methyl-N-(2-pyridylethyl)amino]-m-xylene; synthesized from the reaction between [Cu(2)(L(2)-O)(OH)](ClO(4))(2) and Cl(-)) and Me-L(3)-OH: [Cu(2)(Me-L(3)-O)(mu-X)](ClO(4))(2)xnH(2)O (Me-L(3)-OH = 2,6-bis[N-(2-pyridylethyl)-N-(2-pyridylmethyl)amino]-4-methylphenol and X = C(3)H(3)N(2)(-)(prz), MeCO(2)(-) and N(3)(-)). The magnetochemical characteristics of compounds were determined by temperature-dependent magnetic studies, revealing their antiferromagnetic behaviour [-2J(in cm(-1)) values: -92, -86 and -88; -374].     

Syntheses, characterization, and magnetic studies of copper(II) complexes with the ligand N,N,N',N'-tetrakis(2-pyridylmethyl)-1,3-benzenediamine (1,3-tpbd) and its phenol derivative 2,6-bis[bis(2-pyridylmethyl)amino]-p-cresol] (2,6-Htpcd)

The copper(II) complexes [Cu(4)(1,3-tpbd)(2)(H(2)O)(4)(NO(3))(4)](n)(NO(3))(4n)·13nH(2)O (1), [Cu(4)(1,3-tpbd)(2)(AsO(4))(ClO(4))(3)(H(2)O)](ClO(4))(2)·2H(2)O·0.5CH(3)OH (2), [Cu(4)(1,3-tpbd)(2)(PO(4))(ClO(4))(3)(H(2)O)](ClO(4))(2)·2H(2)O·0.5CH(3)OH (3), [Cu(2)(1,3-tpbd){(PhO)(2)PO(2)}(2)](2)(ClO(4))(4) (4), and [Cu(2)(1,3-tpbd){(PhO)PO(3)}(2)(H(2)O)(0.69)(CH(3)CN)(0.31)](2)(BPh(4))(4)·Et(2)O·CH(3)CN (5) [1,3-tpbd = N,N,N',N'-tetrakis(2-pyridylmethyl)-1,3-benzenediamine, BPh(4)(-) = tetraphenylborate] were prepared and structurally characterized. Analyses of the magnetic data of 2, 3, 4, and [Cu(2)(2,6-tpcd)(H(2)O)Cl](ClO(4))(2) (6) [2,6-tpcd = 2,6-bis[bis(2-pyridylmethyl)amino]-p-cresolate] show the occurrence of weak antiferromagnetic interactions between the copper(II) ions, the bis-terdentate 1,3-tpbd/2,6-tpcd, μ(4)-XO(4) (X = As and P) μ(1,2)-OPO and μ-O(phenolate) appearing as poor mediators of exchange interactions in this series of compounds. Simple orbital symmetry considerations based on the structural knowledge account for the small magnitude of the magnetic couplings found in these copper(II) compounds.     

Zur Thermodynamik der Metallcarbonate. 4. Mitteilung. Potentiometrische Untersuchungen am System Mn2+?CO2?H2O

The solubility and the complex equilibria in the system Mn²⁺-CO₂-H₂O have been investigated at 25°C in solutions of the constant ionic strength 3 M (Na)ClO₄. From experimental data the following values for equilibrium constants and Gibbs free energies of formation are deduced: A predominance area diagram for the system Mn²⁺-H₂-CO_2(g)-H₂S_(g) including MnCO_3(ppt.), α-MnS and Mn²⁺ is given.     

Catalytic and autocatalytic disproportionation reactions of fluorophosphines and related lower valence nonmetal fluorides

In this paper we discuss the mechanism of the related disproportionation reactions 2 RPF₂ → $\text{1}\text{n}$ (RP)_n + RPF₄ 3 R₂PF → R₂P?PR₂ + R₂PF₃ We consider displacement reactions on both fluorine and phosphorus, catalysis and autocatalysis by hydrogen fluoride and the product fluorophosphorane, the effect of substituents on the rate, and iso- electronic analogies involving both other group V atoms and halogens. We also consider related disproportionation reactions of lower valence fluorides of other nonmetals such as S, Cl and Xe. From these comparisons, we deduce the following mechanism (Z = R,F)     

A molecular dynamics study of the dielectric properties of aqueous solutions of alanine and alanine dipeptide

Molecular dynamics simulations were used to compute the frequency-dependent dielectric susceptibility of aqueous solutions of alanine and alanine dipeptide. We studied four alanine solutions, ranging in concentration from 0.13-0.55 mol/liter, and two solutions of alanine dipeptide (0.13 and 0.27 mol/liter). In accord with experiment we find a strong dielectric increment for both solutes, whose molecular origin is shown to be the zwitterionic nature of the solutes. The dynamic properties were analyzed based on a dielectric component analysis into solute, a first hydration shell, and all remaining (bulk) waters. The results of this three component decomposition were interpreted directly, as well as by uniting the solute and hydration shell component to a "suprasolute" component. In both approaches three contributions to the frequency-dependent dielectric properties can be discerned. The quantitatively largest and fastest component arises from bulk water [i.e., water not influenced by the solute(s)]. The interaction between waters surrounding the solute(s) (the hydration shell) and bulk water molecules leads to a relaxation process occurring on an intermediate time scale. The slowest relaxation process originates from the solute(s) and the interaction of the solute(s) with the first hydration shell and bulk water. The primary importance of the hydration shell is the exchange of shell and bulk waters; the self-contribution from bound water molecules is comparatively small. While in the alanine solutions the solute-water cross-terms are more important than the solute self-term, the solute contribution is larger in the dipeptide solutions. In the latter systems a much clearer separation of time scales between water and alanine dipeptide related properties is observed. The similarities and differences of the dielectric properties of the amino acid/peptide solutions studied in this work and of solutions of mono- and disaccharides and of the protein ubiquitin are discussed.