A green and scalable one-pot hydrothermal synthesis generates polyimide/silica hybrid materials, which can be processed by green, solvent-free sintering.

A series of well-defined iron(II) complexes of the types [Fe(PNP)Br-2] and [Fe(PNP)(CO)Br-2] with PNP pincer ligands based on triazine and pyridine backbones were prepared and fully characterized. These complexes were tested as catalysts for the alkylation of amines by alcohols. The high-spin complexes [Fe(PNP)Br-2] are catalytically inactive. The low-spin complexes [Fe(PNP)(CO)Br-2] bearing a carbonyl co-ligand efficiently and selectively convert primary alcohols and aromatic and benzylic amines selectively into mono-N-alkylated amines in good to excellent isolated yields. A mechanistic proposal is given.

Reaction of [Ti4Zr4O6(OBu)4(OMc)16] (OMc = methacrylate) with acetylacetone (acacH) resulted in dissection of the cluster and formation of [Ti(OBu)2(acac)2] and the smaller cluster [Ti2Zr4O4(OMc)16]. In contrast, the same reaction with [Zr6O4(OH)4(OOCR)12]2·6RCOOH (R = Et, CH2CH=CH2) led to site-selective substitution of two carboxylate ligands and formation of isostructural [Zr6O4(OH)4(OOCR)12–x(acac)x]2·6RCOOH (x ≤ 1).

The exchange of the carboxylato ligands of Zr4O2(methacrylato)12 in reactions with carboxylic acids proceeds with retention of the composition and structure of the cluster core. This was concluded from exchange/re-exchange experiments and from comparison of the IR bands of the cluster core of the original and ligand-exchanged clusters. The IR bands were assigned on the basis of DFT calculations. Scrambling reactions between two Zr4O2(OOCR)12 clusters with different carboxylato ligands are a new way to prepare mixed-ligand oxo clusters.

Hydrothermal polymerization (HTP) yields highly crystalline polyimides. A general picture of the mechanisms leading to crystallinity and morphology is provided.

A DFT-based molecular model for imidazolium-silica-based nanoparticle networks (INNs) is presented. The INNs were synthesized and characterized by using small-angle X-ray scattering (SAXS), NMR spectroscopy, and theoretical ab initio calculations. (11)B and (31)P HETCOR CP MAS experiments were recorded. Calculated (19)F NMR spectroscopy results, combined with the calculated anion-imidazolium (IM) distances, predicted the IM chain density in the INN, which was also confirmed from thermogravimetric analysis/mass spectrometry results. The presence of water molecules trapped between the nanoparticles is also suggested. First considerations on possible π-π stacking between the IM rings are presented. The predicted electronic properties confirm the photoluminescence emissions in the correct spectral domain.

In the present study a complete series of seven-coordinate neutral halocarbonyl Mo(II) complexes of the type [Mo(PNPMe-Ph)(CO)2X2] (X I, Br, Cl, F), featuring the new PNP pincer ligand N,N'-bis(diphenyl-phosphino)-N,N'-methyl-2,6-diaminopyridine (PNPMe-Ph), were prepared and fully characterized. The synthesis of these complexes was accomplished by different methodologies depending on the halide ligands. For X = I and Br, [Mo(PNPMe-Ph)(CO)(2)I-2] and [Mo(PNPMe-Ph)(CO)(2)Br-2] were obtained by reacting [Mo(PNPMe-Ph)(CO)(3)] with stoichiometric amounts of I-2 and Br-2, respectively. Alternatively, these complexes were obtained upon treatment of [MoX2(CO)(3)(CH3CN)(2)] (X = I, Br) with 1 equiv. of PNPMe-Ph. On the other hand, in the case of X Cl, [Mo(PNPMe-Ph)(CO)(2)Cl-2] was afforded by the reaction of [Mo(CO)(4)(m-Cl)Cl](2) with 1 equiv. of PNPMe-Ph. The equivalent procedure also worked for X Br. Finally, addition of 1 equiv. of 1-fluoro-2,4,6-trimethylpyridinium tetrafluoroborate to [Mo(PNPMe-Ph)(CO)(3)] yielded the analogous fluorine complex [Mo(PNPMe-Ph)(CO)(2)F-2]. The modification of the ligand scaffold by introducing a Me group instead of H changed the properties of the PNP-Ph ligand significantly. While in the present case exclusively neutral seven-coordinate complexes of the type [Mo(PNPMe-Ph)(CO)(2)X-2] were obtained, with the parent PNP-Ph ligand, i. e., featuring NH spacers, cationic seven-coordinate complexes of the type [Mo(PNP-Ph)(CO)(3)X]X were afforded. DFT calculations indicated that the reactions are under thermodynamic control. The structures of representative complexes were determined by X-ray single crystal analyses. (C) 2014 Elsevier B. V. All rights reserved.

The coordination polymer [Ti(OiPr)3(OOCCH2CH2CH2C3N2H3)] n was prepared from 4-(imidazol-1-yl)butyric acid and titanium isopropoxide. The structure of the compound is remarkable, as the carboxylate group is coordinated in a chelating manner and no dimerization of the Ti(OiPr)3 groups through OR bridges was observed.

Highly promising hybrid materials consisting of silica, titania, or zirconia nanoparticles linked with ionic liquid-like imidazolium units have been developed. The nanoparticle networks are prepared by click-chemistry-like process through a nucleophilic substitution reaction. The type of metal oxide nanoparticles appears to play a key role regarding the pore size of the hybrid material.

In the present study the Mo(0) and W(0) complexes [M(PNP)(CO)3] as well as seven-coordinate cationic hydridocarbonyl Mo(II) and W(II) complexes of the type [M(PNP)(CO)3H]+, featuring PNP pincer ligands based on 2,6-diaminopyridine, have been prepared and fully characterized. The synthesis of Mo(0) complexes [Mo(PNP)(CO)3] was accomplished by treatment of [Mo(CO)3(CH3CN)3] with the respective PNP ligands. The analogous W(0) complexes were prepared by reduction of the bromocarbonyl complexes [W(PNP)(CO)3Br]+ with NaHg. These intermediates were obtained from the known dinuclear complex [W(CO)4(μ-Br)Br]2, prepared in situ from W(CO)6 and stoichiometric amounts of Br2. Addition of HBF4 to [M(PNP)(CO)3] resulted in clean protonation at the molybdenum and tungsten centers to generate the Mo(II) and W(II) hydride complexes [M(PNP)(CO)3H]+. The protonation is fully reversible, and upon addition of NEt3 as base the Mo(0) and W(0) complexes [M(PNP)(CO)3] are regenerated quantitatively. All heptacoordinate complexes exhibit fluxional behavior in solution. The mechanism of the dynamic process of the hydrido carbonyl complexes was investigated by means of DFT calculations, revealing that it occurs in a single step. The structures of representative complexes were determined by X-ray single-crystal analyses.

The bis-carbonyl Fe(II) complex trans-[Fe(PNP-iPr)(CO)2Cl]+ reacts with Zn as reducing agent under a dihydrogen atmosphere to give the Fe(II) hydride complex cis-[Fe(PNP-iPr)(CO)2H]+ in 97% isolated yield. A crucial step in this reaction seems to be the reduction of the acidic NH protons of the PNP-iPr ligand to afford H2 and the coordinatively unsaturated intermediate [Fe(PNPH-iPr)(CO)2]+ bearing a dearomatized pyridine moiety. This species is able to bind and heterolytically cleave H2 to give cis-[Fe(PNP-iPr)(CO)2H]+. The mechanism of this reaction has been studied by DFT calculations. The proposed mechanism was supported by deuterium labeling experiments using D2 and the N-deuterated isotopologue of trans-[Fe(PNP-iPr)(CO)2Cl]+. While in the first case deuterium was partially incorporated into both N and Fe sites, in the latter case no reaction took place. In addition, the N-methylated complex trans-[Fe(PNPMe-iPr)(CO)2Cl]+ was prepared, showing no reactions with Zn and H2 under the same reaction conditions. An alternative synthesis of cis-[Fe(PNP-iPr)(CO)2H]+ was developed utilizing the Fe(0) complex [Fe(PNP-iPr)(CO)2]. This compound is obtained in high yield by treatment of either trans-[Fe(PNP-iPr)(CO)2Cl]+ or [Fe(PNP-iPr)Cl2] with an excess of NaHg or a stoichiometric amount of KC8 in the presence of carbon monoxide. Protonation of [Fe(PNP-iPr)(CO)2] with HBF4 gave the hydride complex cis-[Fe(PNP-iPr)(CO)2H]+. X-ray structures of both cis-[Fe(PNP-iPr)(CO)2H]+ and [Fe(PNP-iPr)(CO)2] are presented.

The treatment of titanium alkoxides with 1,5-pentanedioxime or 2,5-hexanedioxime resulted in the formation of complexes [{TiL(OR)2}2] in which the dioximate ligands (L) bridge a dimeric Ti2(μ2-OR)2 unit. The structures of the complexes were determined by single-crystal structure analysis, ESI mass spectrometry, and 1D and 2D solution NMR spectroscopy. In contrast, the treatment of titanium alkoxides with dioximes bearing cyclic linkers, such as cyclohexyl or aryl groups, resulted in insoluble polymeric compounds. The treatment of various bis(salicylaldiminates) with titanium and zirconium alkoxides resulted in compounds with the same composition [{TiL(OR)2}2], in which, however, two monomeric Ti(OR)2 units are bridged by the ligands L. The two structural possibilities can be distinguished by low-energy collision-induced dissociation owing to their different fragmentation patterns.

0008-6215/$ see front matter 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.carres.2012.12.011 DOI of original article: http://dx.doi.org/10.1016/j.carres.2008.03.029 ⇑ Corresponding author. Tel.: +43 1 36006 6055; fax: +43 1 36006 6059. E-mail address: paul.kosma@boku.ac.at (P. Kosma). z Deceased May 2006. Present Address: Institute of Material Sciences, TU Vienna, Getreidemarkt 9, A-1060 Vienna, Austria. Bent O. Petersen , Margit Sara b,z, Christoph Mader , Harald F. Mayer , Uwe B. Sleytr , Martin Pabst , Michael Puchberger c, , Eberhard Krause , Andreas Hofinger , Jens O. Duus , Paul Kosma c,⇑

Porous, organically modified silica-based mixed oxides were prepared in a two-step process. First, a mixture of tetraethoxysilane, bis(triethoxysilyl)dipropylamine and, optionally, 1,4-bis(triethoxysilyl)benzene was treated with metal chlorides (ZrCl4, TiCl4, or AlCl3), and no water or water-based catalyst was added to the sols. After film formation, the materials were exposed to ambient humidity to achieve hydrolytic condensation of residual groups. Materials with wormhole-like ordered porosity and uniform mesopores were obtained with metal proportions up to about 20?%. According to XPS measurements, the metals are homogenously distributed in the silica matrix.

Zinc(II) complexes with dangling functional organic groups were synthesized by reaction of zinc acetate with a series of bifunctional p-substituted benzene derivatives (a combination of carboxylate, oximate, amino, β-ketoimine, and salicylaldime groups). Selective coordination to carboxylate groups was observed when the second functional group was an oxime or β-ketoimine group. When the second group was an amine or salicylaldimine moiety, these groups were additionally coordinated. From the reaction with p-aminobenzoic acid, the compound [Zn2(OOCCH3)(OOC-C6H4-NH2)3]∞ was crystallized. It is a three-dimensional coordination polymer with bridging aminobenzoate ligands.

A newly arising challenge in the field of nanoparticle research concerns the control and the understanding of the interparticle interactions and interparticle properties. This should allow the development of materials based on nanoparticle assemblies which represents a great opportunity to exploit nanoparticle collective properties. Although some nanoparticle networks have been reported, few works are addressing the highly exciting problem of forming bis-nanoparticle assemblies in which two different types of nanoparticles are present. In this article we report an original synthesis pathway for the formation of an ionic bis-nanoparticle network, silica/silver, based on the formation of an imidazolium bridging unit. The reaction used for the formation of the bridging imidazolium can be considered as click-like chemistry. The synthesis of the metal/metal oxide hybrid composite material starts from the formation of a metal oxide nanoparticle modified with an imidazole ligand. This composite formation is therefore very general and could be extended to other metal/metal oxide composites. .

Titania nanoparticle networks were synthesized by the reaction between imidazole and alkyl halide functionalized anatase nanoparticles. The reaction produced imidazolium bridging units between the nanoparticles that were observed by the means of CP MAS (15)N NMR spectroscopy. The porous characteristics of the obtained nanoparticle network were investigated with nitrogen sorption experiments. From these experiments, a high surface area originating from small mesopores was observed. These results were confirmed by small-angle X-ray diffraction experiments.

A series of cationic palladium ally] complexes of the type [Pd(eta(3)-allyl)(kappa(2)(E,N)-EN-chelate)](+) containing several heterodifunctional EN (E = P, O, S, Se) ligands based on N-(2-pyridinyl)aminophosphines and oxo, thio, and seleno derivatives thereof are prepared. These complexes are studied by one- and two-dimensional NMR techniques together with X-ray and DFT calculations. Variable-temperature and phase-sensitive H-1,H-1 NOESY NMR measurements reveal both allyl and EN ligand dynamics. In the case of palladium, PN complexes' eta(3) to eta(1) isomerization takes place by opening the eta(3)-allyl group selectively at the trans position with respect to the phosphorus center, while for EN (E = O, S, Se) complexes an "apparent" allyl rotation is observed proceeding with Pd E and Pd N bond breaking. DFT calculations indicate that both isomerization processes are solvent assisted, in agreement with the NMR data. In addition, the use of the new palladium allyl complexes has been examined as catalysts for Suzuki-Miyaura coupling of various aryl bromides and arylboronic acids. [Pd(eta(3)-CHPhCHCH2) (ON-Ph)](+), bearing an eta(3)-cinnamyl ligand, is one of the most efficient catalysts, converting aryl bromides and arylboronic acids at 80 degrees C with a catalyst loading of 0.1 mol % quantitatively into the expected biaryl products.

Interactions between a poly(vinyl)silazane and Al2O3 or Y2O3-stabilised ZrO2 fillers were studied during the fabrication of polysilazane-derived bulk ceramics in order to investigate the influence of oxide fillers on resulting properties. Specimens were produced by coating of the filler powders with the polysilazane, warm-pressing of the resulting composite powders, and pyrolytic conversion in flowing N2 at various temperatures between 1000°C and 1400°C. Significant differences in densification were observed, depending on the filler used. Reactions between the polysilazane-derived matrix and Al2O3 or ZrO2 at temperatures ≥1300°C resulted in the formation of Si5AlON7 or ZrSiO4, respectively. Reactivity in the polysilazane-derived component was a result of SiO2 contamination caused primarily by adsorbed species on the filler particle surface. Knowledge of polysilazane/filler interface processes is found to be decisive for the prediction of properties such as shrinkage and porosity, which heavily influence performance of a material.

Several new coordinatively unsaturated iron(II) complexes of the types [Fe(EN-iPr)X-2] (E = P, S, Se; X = Cl, Br) and [Fe(ON-iPr)(2)X]X containing bidentate EN ligands based on N-(2-pyridinyl)aminophosphines as well as oxo, thio, and seleno derivatives thereof were prepared and characterized by NMR spectroscopy and X-ray crystallography. Mossbauer spectroscopy and magnetization studies confirmed their high-spin nature with magnetic moments very close to 4.9 mu (B), reflecting the expected four unpaired d-electrons in all these. compounds. Stable low-spin carbonyl complexes of the types [Fe(PN-iPr)(2)(CO)X]X (X = Cl, Br) and cis-CO,cis-Br-[Fe(PN-iPr)(CO)(2)X-2] (X = Br) were obtained by reacting cis-Fe(CO)(4)X-2 with the stronger PN donor ligands, but not with the weaker EN donor ligands (E = O, S, Se). Furthermore, the reactivity of [Fe(PN-iPr)X-2] toward CO was investigated by IR spectroscopy. Whereas at room temperature no reaction took place, at -50 degrees C [Fe(PN-iPr)X-2] added readily CO to form, depending on the nature of X, the mono- and dicarbonyl complexes [Fe(PN-iPr)(X)(2)(CO)] (X = CO and [Fe(PN-iPr)(CO)(2)X-2] (X = Cl, Br), respectively. In the case of X = Br, two isomeric dicarbonyl complexes, namely, cis-CO,trans-Br-[Fe(PN-iPr)(CO)(2)Br-2] (major species) and cis-CO,cis-Br-[Fe(PN-iPr)(CO)(2)Br-2] (minor species), are formed. The addition of CO to [Fe(PN-iPr)X-2] was investigated in detail by means of DFT/B3LYP calculations. This study strongly supports the experimental findings that at low temperature two isomeric low-spin dicarbonyl complexes are formed. For kinetic reasons cis,trans-[Fe(PN-iPr)(CO)(2)Br-2] releases CO at elevated temperature, re-forming [Fe(PN-iPr)Br-2], while the corresponding cis,cis isomer is stable under these conditions.