Milan Erben

Stibinidene and Bismuthinidene as Two‐electron Donors for Transition Metals (Co and Mn).

The reaction of stibinidene and bismuthinidene ArM [where Ar=C6 H3 -2,6-(CH=NtBu)2 ; M=Sb (1), Bi (2)] with transition metal (TM) carbonyls Co2 (CO)8 and Mn2 (CO)10 produced unprecedented ionic complexes [(ArM)2 Co(CO)3 ](+) [Co(CO)4 ](-) and [(ArM)2 Mn(CO)4 ](+) [Mn(CO)5 ](-) [where M=Sb (3, 5), Bi (4, 6)]. The pnictinidenes 1 and 2 behaved as two-electron donors in this set of compounds. Besides the M→TM bonds, the topological analysis also revealed a number of secondary interactions contributing to the stabilization of cationic parts of titled complexes.

Titanocene(iii) pseudohalides: an ESR and structural study

A series of complexes of the type [Ti(′Cp)2Y] {′Cp = η5-C5H5 (Cp), η5-C5H4SiMe3 (SiCp), η5-1,3-C5H3(Me3Si)2 (Si2Cp); Y = Cl−, CN−, NCS−, NCSe−, dicyanamide (dca), tricyanomethanide (tcm) and 1,2,3,4-thiatriazol-5-thiolate (ttt)} were prepared and studied by ESR spectroscopy. Ring-substituted compounds [Ti(SiCp)2Cl], [Ti(Si2Cp)2Cl], [Ti(SiCp)2CN] and [Ti(Si2Cp)2CN] dissolved in coordinating solvents exist in an equilibrium with solvated species. The thiatriazolthiolate ligand in complexes [Ti(′Cp)2(ttt)] behaves as a S,N-chelator to yield a thermally unstable 4-membered chelate ring having the ESR signal with significant splitting due to coupling with one 14N nucleus. Solutions of [Ti(′Cp)2Y] (Y = NCS−, NCSe−, dca and tcm) readily dissolve the additional pseudohalide salt giving anionic species [Ti(′Cp)2Y2]− with a characteristic ESR pattern caused by super-hyperfine splitting by two 14N nuclei. Cyanide complexes dissolve additional KCN as well, but no coupling to ligand nuclei (neither 14N nor 13C) was observed. The frozen-solution ESR spectra of [Ti(Si2Cp)2Cl], [Ti(Si2Cp)2CN] and [Ti(′Cp)2Y] (Y = NCS−, NCSe− and ttt) are typical for monomeric species of rhombic symmetry. The remaining complexes form dimeric {[Ti(Cp)2Cl]2, [Ti(SiCp)2Cl]2, [Ti(′Cp)2dca]2, and [Ti(′Cp)2tcm]2} or trimeric {[Ti(SiCp)2CN]3} adducts under these conditions. The nuclearity of [Ti(Cp)2CN] cannot be accurately determined by ESR spectroscopy due to its poor solubility but the presence of species with a higher spin ground state was confirmed (similar to the case of the above-mentioned dimers and trimer) by the observation of formally forbidden half-field transition. The reported results of the crystal structure analysis of [Ti(SiCp)2Cl], [Ti(Cp)2tcm], [Ti(SiCp)2tcm], [Ti(SiCp)2dca], [Ti(SiCp)2CN], and [TiCp2(NCS)]2O corroborate the findings based on spectroscopic measurements.

Acetyl­ferrocene–2-chloro-1-ferrocenyl­ethanone (1/1)

In the title co-crystal, [Fe(C5H5)(C7H6ClO)][Fe(C5H5)(C7H7O)], both substituted ferrocene molecules show the expected sandwich structure. The crystal packing exhibits weak intermolecular Cl⋯Cl contacts of 3.279 (4) Å, π–π interactions between the substituted Cp rings of two neighbouring 2-chloro-1-ferrocenylethanone molecules [centroid–centroid distance = 3.534 (3) Å], and weak intermolecular C—H⋯O and C—H⋯Cl hydrogen bonds.

Corrosion protection by organic coatings containing polyaniline salts prepared by oxidative polymerization

The aim of this work was to describe polyaniline salts synthesized and to assess the mechanical and anticorrosion properties of alkyd resin-based coating materials pigmented with them, in dependence on the pigment volume concentration and type. Polyaniline salts were prepared by oxidative polymerization in the solutions of inorganic (hydrochloric, phosphoric, and sulfuric) and organic (p-toluenesulfonic and 5-sulfosalicylic) acids. Polyaniline salts were characterized by thermal analysis and spectroscopic methods. Electrical conductivity was also measured by the van der Pauw method, and the molecular weight of the polyaniline was determined by gel permeation chromatography. Furthermore, the particle size of the solid salts was measured, and the morphology was studied by scanning electron microscopy. Subsequently, the parameters required to formulate pigmented organic coatings, i.e., density and critical pigment volume concentration were determined. A soybean oil-based fast drying alkyd resin of medium oil length was used as the binder for the organic coating material. Organic coatings containing the polyaniline salts at pigment volume concentrations 0%, 1%, 5%, 10%, and 15% were formulated and subjected to a standard accelerated cyclic corrosion tests. The organic coatings (paint films) were also subjected to mechanical tests and to the electrochemical test by potentiodynamic polarization studies.Graphical Abstract

Dibromido[bis­(η5-cyclo­penta­dien­yl)dimethyl­silane]zirconium(IV)

The title molecule, [ZrBr2(C12H14Si)], possesses a crystallographically imposed twofold rotational symmetry with the rotation axis passing through the Zr and Si atoms. The ZrIV centre is in a distorted tetrahedral environment defined by two Cp rings of chelating organic ligands and two Br anions. Two five-membered rings form a dihedral angle of 59.7 (2)°. Unequal Zr—C bonds [2.471 (3)–2.556 (3) Å] in the molecule indicate that the interaction of the central metal with the [(C5H4)2SiMe2]2− ligand contains noticeable η3-allyl and η2-olefin contributions.

{(η5,κN)-[(tert-Butyl­amido)dimethyl­silyl]cyclo­pentadienyl}dichlorotitanium(IV)

The crystal structure of the title compound, [Ti(C11H19NSi)Cl2], has been determined as part of a broad investigation of half-sandwich titanium complexes. Titanium has a pseudo-tetrahedral coordination formed by two Cl atoms [Ti—Cl = 2.2719 (4) and 2.2730 (4) A], the N atom of the N-tert-butyl group [Ti—N = 1.9094 (12) A] and the silyl-substituted Cp ligand [metal–Cp ring centroid distance = 2.0185 (9) A]. The tert-butyl group was found to be disordered.