Immobilization on a Nanomagnetic Co/C Surface Using ROM Polymerization: Generation of a Hybrid Material as Support for a Recyclable Palladium Catalyst

A novel hybrid material is reported as support for a recyclable palladium catalyst via surface immobilization of a ligand onto Co-based magnetic nanoparticles (NPs). A standard “click” reaction is utilized to covalently attach a norbornene tag (Nb-tag) to the surface of the carbon coated cobalt NPs. The hybrid magnetic nanoparticles are produced by initiating polymerization of a mixture containing both Nb-tagged ligand (Nb-tagged PPh 3) and Nb-tagged carbon coated cobalt NPs. In turn, the norbornene units are suitably functionalized to serve as ligands for metal catalysts. A composite material is thus obtained which furnishes a loading that is one order of magnitude higher than the value obtained previously for the synthesis of functionalized Co/C-nanopowders. This allows for its application as a hybrid support with high local catalyst concentrations, as demonstrated for the immobilization of a highly active and recyclable palladium complex for Suzuki-Miyaura cross-coupling reactions. Due to the explicit magnetic moment of the cobalt- NPs, the overall magnetization of this organic/inorganic framework is significantly higher than of polymer coated iron oxide nanoparticles with comparable metal content, hence, its rapid separation from the reaction mixture and recycling via an external magnetic field is not hampered by the functionalized polymer shell

Monomer-on-Monomer (MoM) Mitsunobu Reaction: Facile Purification Utilizing Surface-Initiated Sequestration

A monomer-on-monomer (MoM) Mitsunobu reaction utilizing norbornenyl-tagged (Nb-tagged) reagents is reported, whereby purification was rapidly achieved by employing ring-opening metathesis polymerization which is initiated by any of three methods utilizing Grubbs catalyst (i) free catalyst in solution, (ii) surface-initiated catalyst-armed silica or (iii) surface-initiated catalyst-armed Co/C magnetic nanoparticles

Immobilization of homogeneous catalysts on nanoparticles and their application in semi-heterogeneous catalysis

It was the aim of this work to develop a generally applicable strategy for the immobilization of catalysts on different nanoparticles with particular interest in the �heterogenization� of chiral azabis(oxazolines), which represent a predestined class of ligands for the grafting on solid supports due to their central nitrogen atom. To this end, a copper(I)-catalyzed azide/alkyne cycloaddition (CuAAC) reaction was envisaged to be the most versatile tagging method, allowing even the use of preformed transition-metal complexes after according derivatization with an alkyne moiety. Such a route was expected to provide distinct advantages over the in-situ complexation by adding the equivalent amount of metalsalt to the immobilized ligand, since the exact determination of ligand loading is challenging. This issue was aggravated by recent investigations from Reiser et al., indicating that not only an excess of transition metal has a detrimental effect on the optical yields attained, but also a ligand surplus is capable of diminishing the level of enantioselectivity in certain reactions. Whereas the negative influence of uncomplexed metal centers on the ee-values obtained is apparent, since no stereodiscriminating environment is coined to the catalytic center by a chiral ligand, the elucidation of the mechanism of the unprecedented effect of ligand surplus was considered highly relevant for immobilized ligands on any type of support. Thus, preliminary investigations focused on the understanding of this effect with the aim to develop strategies, which could help circumventing the negative influence of ligand excess in the reactions affected. Azabis(oxazoline) ligands and azabis(oxazoline)-copper(II) complexes respectively were successfully immobilized on superparamagnetic magnetite@silica- and ferromagnetic carbon coated cobalt-nanoparticles using a concise �click� protocol. Propargylated azabis(oxazoline)-ligands and Cu(II)-complexes were equally active in the CuAAC reaction with the azide functionalized core/shell materials, resulting in quantitative conversion of the azide moieties. The material thus obtained, proved to be highly active and selective in the asymmetric monobenzoylation of racemic 1,2-diols. Magnetite@silica-nanoparticle supported catalyst could be recycled via magnetic decantation after each run and proved to be active in at least five consecutive batch reactions without any significant drop in selectivity. Co/C-nanoparticle supported catalyst was as active at batch conditions and allowed the implementation of the nanomagnets in a closed circuit-type reactor under continuous-flow conditions. The high saturation magnetization of the ferromagnetic cobalt cores allowed those particles to act as their own nanosized stirrers in a microreactor that was operated vertically between adjacent parallel flanks of two magnetic stir motors

Dynamics on real estate and emerging markets

While much attention has focused on the modelling of the interdependencies between key aggregates and stock indices in industrialised countries, this thesis is focused on investments in emerging markets and real estate � two research branches that have up to now not been investigated to a comparable extent. The analysis of individual scientific issues therefore contributes to improving the understanding of conditions and essential interrelationships in these markets and sectors. Within the scope of the present thesis, the empirical results are mainly based on the Johansen (1988) procedure. The use of vector error correction models (VECM) guarantees that the dynamic character among the selected determinants is taken into account and furthermore allows the evaluation of both the long-term equilibrium relationships and the channels during the adjustment process after deviations from the long-term trend. In addition, the empirical results are verified by employing further analyses in order to gain deeper insights into the respective scientific issue. In Chapter 2 the study examines �Macroeconomic Effects on Emerging Market Sector Indices�. As emerging countries continue to gain in importance for the world economy, it is worthwhile extending research into regions that have up to now been comparatively neglected. Contrary to the a priori defined hypotheses, the majority of the exam-ined sectors benefited from increasing commodity prices during the examination sample. As a result, this finding provides empirical evidence on the suspicion that the ongoing catching-up process and the consequential growth in affluence in the emerging countries is largely driven by growing commodity prices and exports. According to that, not only those sectors which are closely linked to commodity trade activities benefit from rising prices. Instead, via the channels of increasing consumption rates and growing domestic purchasing power within the emerging economies, the remaining sectors also benefit from the increase in export earnings. In contrast to Chapter 2, which conducts a cross-sectoral comparison, the fol-lowing chapters are focused on the real estate sector in particular. The scientific approach of Chapter 3 is similar to the first one and is focused on �The Link between Property and Economy� in the German and British real estate markets. On a long-term basis, the results of the implemented VEC models indicate re-markable similarities between both examined real estate markets. Accordingly, in spite of the outlined differences, the long-term equilibrium is determined by the same factors indicating the same signs and the same magnitude of coeffi-cients. Consequently, the empirical results clarify that the fundamental role of property markets in an economy dominates country-specific characteristics in the long run. The distinctive features of the national property markets, however, are primarily relevant during the adjustment process after deviations from the long-term equilibrium. Although the economic environment is also considered in Chapter 4, this study is primarily aimed at the scientific issue of whether real estate stock indices in the United States and the United Kingdom are predominantly driven by the underlying property markets or by progress on general stock markets. For this purpose, an alternative approach is used. Instead of focussing only on the assets of real estate equities, direct real estate and stock indices � as was frequently done in previous studies � the macroeconomic environment is here explicitly taken into account in each country. As real estate markets are known to be cyclical in nature (Lizieri et al., 1998), it is therefore supposed that the structure of market behaviour differs across phases of boom and bust. This might be recognisable by lower adjustment velocities after deviations from the equilibrium or by different volatilities of property values depending on the economic situation. Accordingly, the implemented methods indicate a significantly stronger linkage among the real estate assets compared to the equity assets in the long run. Therefore, this study clarifies that long-term investments in real estate equity indices still fulfil their function as an alternative investment in order to diversify an investor´s portfolio

The links between property and the economy - evidence from the British and German markets

This study supplies empirical evidence on the dynamic interactions between the property markets in Germany and the United Kingdom and their country-specific macroeconomic environment. Using a VECM framework, the findings contribute to improving the evaluation of the properties' behaviour by considering a wide range of macroeconomic risk factors. On a long-term basis, we find remarkable similarities between both examined real estate markets with respect to significance, signs and magnitude of coefficients, despite essential differences in terms of market structure, conditions and performance. This suggests that the fundamental role of property markets in an economy dominates the country-specific characteristics in the long run. However, the distinctive features of the national property markets, including differences with respect to the financial systems, are primarily relevant during the short-term adjustment process back to the long-term equilibrium