Eberhardt Herdtweck

Bio: Eberhardt Herdtweck is an academic researcher from Ludwig Maximilian University of Munich. The author has contributed to research in topics: Rhenium & Cyclopentadienyl complex. The author has an hindex of 49, co-authored 280 publications receiving 7641 citations. Previous affiliations of Eberhardt Herdtweck include University of Siena & Chemical Research Center of the Hungarian Academy of Sciences.

Octahedral bipyridine and bipyrimidine dioxomolybdenum(VI) complexes: characterization, application in catalytic epoxidation, and density functional mechanistic study.

Abstract: Complexes of the general formula [MoO 2 X 2 L 2 ] (X=Cl, Br, Me; L 2 =bipy, bpym) have been prepared and fully characterized, including X-ray crystallographic investigations of all six compounds. Additionally, the highly soluble complex [MoO 2 Cl 2 (4,4'-bis(hexyl)-2,2'-bipyridine)] has been synthesized. The reaction of the complexes with tert-butyl hydroperoxide (TBHP) is an equilibrium reaction, and leads to Mo V I η 1 -alkylperoxo complexes that selectively catalyze the epoxidation of olefins. Neither the Mo-X bonds nor the Mo-N bonds are cleaved during this reaction. These experimental results are supported by theoretical calculations, which show that the attack of TBHP at the Mo center through the X-O-N face is energetically favored and the TBHP hydrogen atom is transferred to a terminal oxygen of the Mo=O moiety. After the attack of the olefin on the Mo-bound peroxo oxygen atom, epoxide and tert-butyl alcohol are formed. The latter compound acts as a competitive inhibitor for the TBHP attack, and leads to a significant reduction in the catalytic activity with increasing reaction time.

Synthesis of the First Gold(I) Carbene Complex with a Gold‐Oxygen Bond — First Catalytic Application of Gold(I) Complexes Bearing N‐Heterocyclic Carbenes

Abstract: A series of silver(I) and gold(I) carbene complexes of the type [Ag(R2-imy)2]+[AgBr2]— and [Au(R2-imy)X] (R2-imy = 1-diphenylmethyl-3-methyl-imidazol-2-ylidene; X = Cl, OC(O)CH3) have been prepared and structurally characterized. The complex [Au(R2-imy) OC(O)CH3] is the first gold(I) carbene complex with a gold-oxygen bond. The results of a single crystal structure determination of this gold(I) carbene acetate are similar to those of the analogous (triphenylphosphane)gold(I) acetate. The gold oxygen distance Au-O1 with 2.040(4)A parallels the majority of (phosphane)gold(I) carboxylates. Furthermore we successfully employed the Au(I) carbene acetate as a catalyst for the addition of water to 3-hexyne in the presence of a Lewis acid as co-catalyst. This is the first example for the use of a gold(I) carbene complex in homogeneous catalysis. Darstellung des ersten Gold(I)-Carben-Komplexes mit einer Gold-Sauerstoff Bindung — erste katalytische Anwendung von Gold(I)-Komplexen N-heterocyclischer Carbene Eine Reihe neuer Silber(I)- und Gold(I)-Carben-Komplexe vom Typ [Ag(R2-imy)2]+[AgBr2]— und [Au(R2-imy)X] (R2-imy = 1-diphenylmethyl-3-methyl -imidazol-2-yliden; X = Cl, OC(O)CH3) wurden dargestellt und strukturell charakterisiert. Der Komplex [Au(R2-imy) OC(O)CH3] ist der erste Vertreter eines Gold(I)-Carben-Komplexes mit einer Gold-Sauerstoff-Bindung. Die Ergebnisse einer Einkristall-Rontgenstrukturananlyse dieser Verbindung entsprechen denen des analogen (Triphenylphosphan)gold(I)-Acetats. Der Gold-Sauerstoff-Abstand von 2.040(4)A ist ebenfalls ahnlich mit den Werten, die fur bereits publizierte (Phosphan)gold(I)-Komplexe mit Gold-Sauerstoffbindung gefunden wurden. Im folgenden wurde das NHC-Au(I)-Acetat erfolgreich als Katalysator fur die Addition von Wasser an 3-Hexin in Anwesenheit einer Lewis-Saure als Cokatalysator eingesetzt. Dies ist unserer Kenntnis nach das erste Beispiel fur die Anwendung eines Gold(I)-Carben-Komplexes in der Homogenkatalyse.

Mechanistic insights into heterogeneous zinc dicarboxylates and theoretical considerations for CO2-epoxide copolymerization.

Abstract: Copolymerization of epoxides and CO(2) with heterogeneous zinc dicarboxylates is prominent since the early days of this area of chemistry. However, in over 30 years of research, the efficiency of this catalyst system could not be improved significantly. Furthermore, a huge activity difference between zinc glutarate and its lower homologue zinc succinate exists, which could not be explained so far. A detailed investigation of the underlying copolymerization mechanisms on heterogeneous catalysts is therefore necessary. Such investigations are so far lacking, which renders logical improvements of the catalysts difficult. We therefore decided to conduct a detailed investigation on the different zinc-dicarboxylic catalysts, their copolymerization efficiency, solid state structure and supplemented the results with theoretical calculations. The results imply that the widely discussed bimetallic mechanism (for homogeneous catalysts) is in place for heterogeneous zinc dicarboxylates as well. Theoretical calculations conducted to identify an "ideal" Zn-Zn distance suggest an optimal separation of Zn atoms in the range of 4.3-5.0 A. The combined copolymerization experiments and calculated models give a consistent explanation for the difference in activity of the different zinc-dicarboxylate catalysts and give a hint why the activity of the heterogeneous zinc-dicarboxylate system is limited.

Multicomponent Reactions with Isocyanides.

Abstract: Multicomponent reactions (MCRs) are fundamentally different from two-component reactions in several aspects. Among the MCRs, those with isocyanides have developed into popular organic-chemical reactions in the pharmaceutical industry for the preparation of compound libraries of low-molecular druglike compounds. With a small set of starting materials, very large libraries can be built up within a short time, which can then be used for research on medicinal substances. Due to the intensive research of the last few years, many new backbone types have become accessible. MCRs are also increasingly being employed in the total synthesis of natural products. MCRs and especially MCRs with isocyanides offer many opportunities to attain new reactions and basic structures. However, this requires that the chemist learns the “language” of MCRs, something that this review wishes to stimulate.

N-heterocyclic carbenes: a new concept in organometallic catalysis.

Abstract: N-Heterocyclic carbenes have become universal ligands in organometallic and inorganic coordination chemistry. They not only bind to any transition metal, be it in low or high oxidation states, but also to main group elements such as beryllium, sulfur, and iodine. Because of their specific coordination chemistry, N-heterocyclic carbenes both stabilize and activate metal centers in quite different key catalytic steps of organic syntheses, for example, C-H activation, C-C, C-H, C-O, and C-N bond formation. There is now ample evidence that in the new generation of organometallic catalysts the established ligand class of organophosphanes will be supplemented and, in part, replaced by N-heterocyclic carbenes. Over the past few years, this chemistry has been the field of vivid scientific competition, and yielded previously unexpected successes in key areas of homogeneous catalysis. From the work in numerous academic laboratories and in industry, a revolutionary turning point in oraganometallic catalysis is emerging.