Synthesis of novel cyclopentadienyl cobalt(I)-complexes and their application in [2+2+2] cycloaddition reactions

This thesis describes the synthesis of cyclopentadienyl (Cp) cobalt(I)-complexes of the type [CpCo(I)L1L2]. Systematic variation of the neutral ligands (L) demonstrated that the use of two different ligands – namely an olefin and a phosphite ligand – proved to be superior to the homoleptic equivalents, providing sufficient activity in catalytic [2+2+2] cycloaddition reactions as well as appropriate stability. Further modifications resulted in air-stable and recyclable catalysts, which could be supported on a solid-phase, representing the first active, supported, CpCo(I)-based catalyst

CO2 Hydrogenation: Supported Nanoparticles vs. Immobilized Catalysts

The conversion of CO2 to more valuable chemicals has been the focus of intense research over the past decades, and this field has become particularly important in view of the continuous increase of CO2 levels in our atmosphere and the need to find alternative ways to store excess energy into fuels. In this review we will discuss different strategies for CO2 conversion with heterogeneous and homogeneous catalysts. In addition, we will introduce some promising research concerning the immobilization of homogeneous catalysts on heterogeneous supports, as a hybrid of hetero- and homogeneous catalysts

Ruthenium piano-stool complexes bearing imidazole-based PN ligands

A variety of piano-stool complexes of cyclopentadienyl ruthenium(II) with imidazole-based PN ligands have been synthesized starting from the precursor complexes CpRu(C10H8)]PF6, CpRu(NCMe)(3)]PF6 and CpRu(PPh3)(2)Cl]. PN ligands used are imidazol-2-yl, -4-yl and -5-yl phosphines. Depending on the ligand and precursor different types of coordination modes were observed; in the case of polyimidazolyl PN ligands these were kappa P-1-monodentate, kappa P-2,N-, kappa N-2,N- and kappa N-3,N,N-chelating and mu-kappa P:kappa N-2,N-brigding. The solid-state structures of CpRu(1a)(2)Cl]center dot H2O (5 center dot H2O) and {CpRu(mu-kappa(2)-N,N-kappa('1)-P-2b)}(2)](C6H5PO3H)(2)(C6H5PO3H2)( 2), a hydrolysis product of the as well determined {CpRu(2b)} (2)](PF6)(2)center dot 2CH(3)CN (7b center dot 2CH(3)CN) were determined (1a = imidazol-2-yldiphenyl phosphine, 2b = bis(1-methylimidazol-2-yl) phenyl phosphine, 3a = tris(imidazol-2-yl) phosphine). Furthermore, the complexes CpRu(L)(2)]PF6 (L = imidazol-2-yl or imidazol-4-yl phosphine) have been screened for their catalytic activity in the hydration of 1-octyne. (C) 2011 Elsevier B. V. All rights reserved

Efficient CO2 hydrogenation to formate with immobilized Ir-catalysts based on mesoporous silica beads

ISSN:0947-6539ISSN:1521-376

CO 2

The conversion of CO2 to more valuable chemicals has been the focus of intense research over the past decades, and this field has become particularly important in view of the continuous increase of CO2 levels in our atmosphere and the need to find alternative ways to store excess energy into fuels. In this review we will discuss different strategies for CO2 conversion with heterogeneous and homogeneous catalysts. In addition, we will introduce some promising research concerning the immobilization of homogeneous catalysts on heterogeneous supports, as a hybrid of hetero- and homogeneous catalysts

Site-isolated manganese carbonyl on bipyridine-functionalities of periodic mesoporous organosilicas: efficient CO2 photoreduction and detection of key reaction intermediates

Well-defined and fully characterized supported CO2 reduction catalysts are developed through the immobilization of an earth abundant Mn complex on bpy-PMO (bpy = bipyridine; PMO = Periodic Mesoporous Organosilica) platform materials. The resulting isolated Mn-carbonyl centers coordinated to bipyridine functionalities of bpy-PMO catalyze the photoreduction of CO2 into CO and HCOOH with up to ca. 720 TON in the presence of BIH (1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzoimidazole), used as the electron donor. A broad range of photochemical conditions (varying solvents, sacrificial electron donors, photosensitizer type and concentration, catalyst loading as well as the Mn loading within the PMO) are investigated, demonstrating high activity even for simple organic dyes and Zn-porphyrin as photosensitizers. Spectroscopic and catalytic data also indicate that site isolation of the Mn complex in the PMO framework probably inhibits bimolecular processes such as dimerisation and disproportionation and thus allows the spectroscopic observation of key reaction intermediates, namely the two meridional isomers of the carbonyl complexes and the bipyridine radical anion species.ISSN:2041-6520ISSN:2041-653

Probing the molecular character of periodic mesoporous organosilicates: Via photoluminescence of Lewis acid-base adducts

Photoluminescence decay was used as a structure-sensitive method to compare the distribution of emitting sites in periodic mesoporous organosilicates (PMOs) to their respective molecular analogs. The observed close similarity of PL decays confirms the molecular nature of PMOs and high homogeneity of emitting sites.ISSN:1463-9084ISSN:1463-907

CoCl(PPh₃)₃ as Cyclotrimerization Catalyst for Functionalized Triynes under Mild Conditions

The ubiquitary Co­(I) complex CoCl­(PPh₃)₃ was found to be a convenient catalyst for the [2 + 2 + 2] cycloaddition of functionalized triynes under mild reaction conditions and devoid of any additional additive, yielding the substituted arene compounds. Successful development of synthetic routes to various triynes and the subsequent cyclotrimerization key step gave systematic access to a variety of different bi- and triaryls with good to excellent yields for the cyclization

Synthesis and Catalytic Activity of [Cp′Co(COD)] Complexes Bearing Pendant N‑Containing Groups

The novel Co­(I)-complex [Cp^CNCo­(COD)] (Cp^CN = η⁵-(C₅H₄CMe₂CH₂CN), COD = 1,5-cyclooctadiene; <b>3</b>) with a substituted cyclopentadienyl ligand containing a pendant nitrile moiety has been synthesized and characterized by X-ray diffraction. The reactivity of the nitrile group in <b>3</b> has been investigated regarding its behavior in cyclization reactions with alkynes, leading to three new complexes containing pendant 2-pyridyl groups. All synthesized complexes have been evaluated as catalysts in the [2 + 2 + 2] cycloaddition reaction of 1,6-heptadiyne and benzonitrile