Synthesis and reactivity of [Au(NHC)(Bpin)] complexes

The authors gratefully acknowledge the Royal Society (University Research Fellowship to C.S.J.C.), AstraZeneca (Studenship to C.M.Z) and VLAIO (CO2PERATE) for support of this work. We thank King Saud University (DSF Program) and KAUST (Award No.OSR-2015-CCF-1974-03) for support.A new class of [Au(NHC)(Bpin)] complexes has been synthesized and their unusual reactivity was investigated using computational and experimental methods. The gold-boryl complexes exhibit unexpected high stability and reactivity.PostprintPeer reviewe

ANALIZA SUSTAVA ZA UNUTARNJE LOCIRANJE

Recently, due to advances in the development of various technologies which can be used for locating, it is possible to develop systems which include software solutions for the user locationing and guidance in the interior, closed or covered areas where the existing location technologies and systems for locating and guidance applicable at open, outdoor areas cannot be used. This paper analyses the available hardware, software and network technologies which can be used for creating a positioning system for interior, closed or covered area. The paper analyses technologies which can be used in such distributed systems for the implementation of functionalities that are needed or required in the Indoor Positioning System (IPS). The paper describes the concept of the IPS system. It presents the IPS systems available on the market. It shows the technologies that can be used to implement the IPS system and the analyses of categories which affect the IPS system implementation. The paper demonstrates that none of the technologies analysed meet all of the observed categories while the BLE technology achieves the most favourable results in individual categories.Zbog napretka u razvoju raznih tehnologija koje se mogu koristiti za lociranje, u posljednje vrijeme razvijaju se sustavi koji uključuju programska rješenja za lociranje i navođenje korisnika u unutarnjem, zatvorenom ili natkrivenom prostoru, gdje se postojeće tehnologije za lociranje i sustavi za lociranje i navođenje koje se primjenjuju kod otvorenih, vanjskih prostora, ne mogu koristiti. U radu se analiziraju dostupne hardverske, softverske i mrežne tehnologije kojima je moguće izraditi sustav za unutarnje lociranje, odnosno tehnologije kojima takav distribuirani sustav po svom karakteru i implementiranim funkcijama postaje sustav za lociranje u zatvorenom prostoru (IPS, engl. Indoor Positioning System). Opisan je koncept IPS sustava. Prikazani su gotovi IPS sustavi dostupni na tržištu. Pokazane su tehnologije koje se mogu koristiti za implementaciju IPS-a i izrađena analiza kategorija koje utječu na implementaciju IPS-a. Pokazano je da niti jedna tehnologija ne zadovoljava sve promatrane kategorije, no BLE tehnologija omogućuje ostvarenje najpovoljnijih rezultata po pojedinim kategorijama

Imidazole to NHC rearrangements at molybdenum centers. An experimental and theoretical study

El pdf del artículo es la versión de autor.-- et al.Both manganese and rhenium complexes of the type [M(bipy)(CO)3(N-RIm)]+ (bipy=2,2’-bipyridine) undergo deprotonation of the central CH group of the N-alkylimidazole (N-RIm) ligand when treated with a strong base. However, the outcome of the reaction is very different for either metal. For Mn, the addition of the equimolar amount of an acid to the product of the deprotonation affords an N-heterocyclic carbene (NHC) complex, whereas for Re, once the deprotonation of the central imidazole CH group has occurred, the bipy ligand undergoes a nucleophilic attack on an ortho carbon, affording the C--C coupling product. The extension of these studies to pseudo-octahedral [Mo(η3-allyl)(bipy)(CO)2(N-RIm)]+complexes has allowed us to isolate cationic NHC complexes (MnI-type behavior), as well as their neutral imidazol-2-yl precursors. Theoretical studies of the reaction mechanisms using DFT computations were carried out on the deprotonation of [Mn(bipy)(CO)3(N-PhIm)]+, [Re(bipy)(CO)3(N-MesIm)]+, and [Mo(η3-C4H7)(bipy)(CO)2(N-MesIm)]+ complexes (Mes=mesityl) at the B3LYP/6-31G(d) (LANL2DZ for Mn, Re, and Mo) level of theory. Our results explain why different products have been found experimentally for Mn, Mo, and Re complexes. For Re, the process leading to a C_C coupling product is clearly more favored than those forming an imidazol-2-yl product. In contrast, for Mn and Mo complexes, the lower stabilizing interaction between the central imidazole and ortho bipy C atoms, along with the higher lability of the ligands, make the formation of an NHC-type product kinetically more accessible, in good agreement with experimental findings.Financial support from the Ministerio de Ciencia e Innovación (MICINN, project number CTQ2009–12366) and Principado de Asturias (project number IB08–104) is gratefully acknowledged.Peer Reviewe

Synthesis and characterization of gold(I) complexes of dibenzotropylidene-functionalized NHC ligands (Trop-NHCs)

The ERC (Advanced Investigator Award-FUNCAT), Syngenta, and the EPSRC are gratefully thanked for support of this work. S.P.N. is a Royal Society Wolfson Research Merit Award holder.Gold(I) complexes of dibenzotropylidene-functionalized N-heterocyclic carbene ligands (Trop-NHCs) have been prepared in order to investigate their structural features and to reveal possible interactions of the olefin unit with the metal center. The precursor imidazolium chloride salts (R-1) were generated in a single step using N-substituted imidazoles (R = H, Me, DiPP, Ad) and 1 or 2 equiv of Trop-Cl, generating unsymmetrical and symmetrical NHC-olefin hybrids. The structural parameters of the ligands were determined by synthesis and X-ray diffraction analysis of their corresponding gold(I) chloride complexes, revealing highly flexible steric demands of the Trop unit. Conversion of these complexes with halide-abstracting reagents such as AgNTf2 and NaBArF24 cleanly gave neutral, NTf2-coordinated complexes of the type [(NHC)Au(NTf2)] (R-3) and the cationic bis-NHC-coordinated complexes [(NHC)2Au]BArF24 (R-4), respectively. The Gagosz-type complexes R-3 were further tested in the hydration of diphenylacetylene, showing a clear trend in activity depending on the ligand’s sensitivity to hydrolysis.PostprintPeer reviewe

Transition metal-catalyzed carboxylation of organic substrates with carbon dioxide

The development of sustainable chemical processes is a long-standing challenge. Carbon dioxide represents a renewable C1 building block for organic synthesis and industrial applications as an alternative to other common feedstocks which are based on natural gas, petroleum oil, or coal. Apart from the advantages associated with the nontoxicity and abundance of CO2, its utilization further enables the reduction in its atmospheric content, which contributes significantly to the greenhouse effect. Although widespread application of CO2 in organic synthesis - even on an industrial scale - will not be able to fully compensate for the steadily increasing atmospheric quantities produced (mainly by the combustion of fuels), ecological and economical factors make its usage highly desirable. Therefore, tremendous efforts toward activation and utilization of CO2 have been made by the scientific community over the last 30 years, and, as a result, the number of highly efficient transition metal-catalyzed CO2-incorporative reactions has increased dramatically, especially within the last decade. The achievements in the development of sustainable and economic chemical processes for the carboxylation of organic molecules with CO2 are presented in detail in this chapter

Transition metal-catalyzed carboxylation of organic substrates with carbon dioxide

The development of sustainable chemical processes is a long-standing challenge. Carbon dioxide represents a renewable C1 building block for organic synthesis and industrial applications as an alternative to other common feedstocks which are based on natural gas, petroleum oil, or coal. Apart from the advantages associated with the nontoxicity and abundance of CO2, its utilization further enables the reduction in its atmospheric content, which contributes significantly to the greenhouse effect. Although widespread application of CO2 in organic synthesis – even on an industrial scale – will not be able to fully compensate for the steadily increasing atmospheric quantities produced (mainly by the combustion of fuels), ecological and economical factors make its usage highly desirable. Therefore, tremendous efforts toward activation and utilization of CO2 have been made by the scientific community over the last 30 years, and, as a result, the number of highly efficient transition metal-catalyzed CO2-incorporative reactions has increased dramatically, especially within the last decade. The achievements in the development of sustainable and economic chemical processes for the carboxylation of organic molecules with CO2 are presented in detail in this chapter

1,2-Bis(di-<i>tert</i>-butylphosphino)imidazole (<b>dtbpi</b>): A Versatile Imidazole-Based, Rigid, Bulky Bisphosphine Ligand for Transition Metals

A bulky bisphosphine, 1,2-bis­(di-<i>tert</i>-butylphosphino)­imidazole (<b>dtbpi</b>), featuring a rigid imidazole backbone, was synthesized in a simple two-step procedure. The ligand’s coordination chemistry and electron-donating abilities were investigated in the complexes (<b>dtbpi</b>)­Ni­(FDN) (<b>3</b>) and [(<b>dtbpi</b>)­Rh­(CO)₂]­BF₄ (<b>4</b>). Protonation of <b>4</b> at the ligand backbone’s nitrogen with strong Brønsted acids such as HBF₄ and HBAr_F gave the dicationic dicarbonyl complexes [(<b>H-dtbpi</b>^<b>+</b>)­Rh­(CO)₂]­(BF₄)­(BAr_F) (<b>5a</b>) and [(<b>H-dtbpi</b>^<b>+</b>)­Rh­(CO)₂]­(BF₄)₂ (<b>5b</b>), which served as model complexes of the ligand’s imidazolium-phosphine form and permitted characterization of its donating character. In order to evaluate solely the different electronic characters of the two isosteric P donors, the complexes (<b>dtbpi</b>)­PdCl­(Me) (<b>6</b>) and [(<b>dtbpi</b>)­RhCl]₂ (<b>7</b>) were synthesized. An unexpected rearrangement of one of the formed stereoisomers of <b>6</b>, with cleavage of an N–P bond, was found. A novel phosphine-phosphonium ylide ligand (<b>8</b>) has been made accessible via chemoselective alkylation of the carbon-bound P donor of <b>dtbpi</b> to yield the phosphonium salt [<i>P</i>-CH₃-dtbpi]­BF₄ (<b>2</b>). The ylide <b>8</b> was generated in situ by deprotonation of <b>2</b> with KHMDS. Its coordination to the PdCl­(Me) fragment led to the isolation of exclusively the <i>Z</i> isomer of [(<b>8</b>)­PdCl­(Me)] (<b><i>Z</i>-9</b>). X-ray structure analysis of [(<b>dtbpi</b>)­Rh­(NBD)]­BF₄ (<b>10</b>) and its dicationic analogue [(<b>H-dtbpi</b>^<b>+</b>)­Rh­(NBD)]­(BF₄)­(BAr_F) (<b>11</b>) revealed the structural changes provoked upon ligand backbone protonation

Gold-N-heterocyclic carbene complexes of mineral acids

We have synthesized and characterized new gold-N-heterocyclic carbene (NHC) complexes derived from the deprotonation of mineral acids. The use of sulfuric acid was a particularly interesting case. These complexes were tested in known gold-catalyzed reactions, such as the hydration of alkynes and the Meyer-Schuster rearrangement. They proved to be highly efficient in both reactions

A simple synthetic entryway into palladium cross-coupling catalysis

The simple synthesis of a family of palladates containing an imidazolium counterion is presented. These ''ate'' complexes can be easily converted into well-defined palladium-N-heterocyclic carbene (NHC) complexes. The synthetic protocols leading to the ''ate'' and to the Pd-NHC neutral complexes have been exemplified with various NHC ligands. The palladates prove efficient pre-catalysts enabling Suzuki-Miyaura and Mizoroki-Heck reactions.</p

Individuelle Impfpräferenz in Rheinland Pfalz 2007-2009 an Hand der Schuleingangsuntersuchungen

Loss of articular cartilage surface integrity is considered the earliest sign of osteoarthritis; however, its reliable detection has not been established by clinical routine diagnostics. This study comprehensively assesses a set of 11 algorithm-based 2-D Optical Coherence Tomography roughness parameters and investigates their clinical impact. Histology and manual irregularity quantification of 105 human cartilage samples with variable degeneration served as reference. The majority of parameters revealed a close-to-linear correlation with the entire spectrum of degeneration. Surface integrity should therefore be assessed by a combination of parameters to improve current diagnostic accuracy in the determination of cartilage degeneration