Di- and polymetallic heteroatom stabilized (Fischer) metal carbene complexes.

σ,π-Bridging Ligands in Bimetallic and Trimetallic Complexes

Metalloxy Fischer Carbene Complexes: An Efficient Strategy to Modulate Their Reactivity

A large number of ternary hydrides of transition metals and alkali or alkaline earth metals have been synthesized and structurally characterized in the last twenty years. These compounds exhibit a puzzling variety of compositions, transition metal coordination numbers, transition metal coordination geometries, and distribution of hydrides within and outside of the transition metal coordination sphere. Valence Bond (VB) concepts form a theoretical framework for understanding, at least partially, some of the dominant trends observed among various transition metal hydride structures. Extrapolation of these concepts suggests that synthesis of ternary metal hydrides with formal electron counts at the transition metal exceeding 18 electrons may be feasible.

Structure and Electron Counting in Ternary Transition Metal Hydrides

Group 4 ketimide complexes: Synthesis, reactivity and catalytic applications

Monitoring the electronic features of rigid C1-bridged Group 4 ansa-metallocenes by using the dynamic and structural properties of their s-cis-η4-butadiene complexes

A Template Synthesis of Stable Conjugated Primary Enamines from Ketones, Nitriles, and Butadiene

Butadiene is 1,4-selectively coupled with a metal carbonyl and a ketone at the bis(η-cyclopentadienyl)zirconium template to yield the nine-membered metallacyclic products 3. Subsequent hydrolysis under oxidative conditions (pyridine N-oxide) gives the corresponding substituted b-hydroxy-3-hexenoic acids 5. By this procedure a -CH 2 CH=CHCH 2 CO 2 H nucleophile has thus formally been added to the ketone substrate. Esterification of 5 followed by treatment with a base converts these organic template coupling products into substituted tetrahydrofuran acetic acids. Similarly, ketones are linearly coupled with butadiene and a nitrile to yield analogously structured hydroxyalkenones 15 which undergo acid catalyzed ring closure to yield the -CH 2 COR substituted tetrahydrofurans 16

Syntheses of substituted 6-hydroxyhexenoic acids and related tetrahydrofuran systems by metallocene-template directed 1,4-selective coupling of 1,3-butadiene with carbonyl compounds

The reaction of (butadiene)zirconocene with hexacarbonyltungsten gives the metallacyclic [(π-allyl)zirconoxy]carbene complex 7 This reagent adds to a variety of ketones to yield chiral nine-membered metallacyclic ring systems (8) These systems are thus formed by means of 1,4-selective coupling reactions of 1,3-butadiene with W(CO)6 and an organic carbonyl compound at the zirconocene template The ketones subjected to react with 7 include benzophenone, methyl vinyl ketone, cyclopentanone, and 3-methoxyestra-1,3,5(10)-trien-17-one (12) The coupling products of 7 with cyclopentanone (8c) and 12 (8d-A) were characterized by X-ray crystal structure analyses Of the four possible diastereomeric nine-membered metallacyclic coupling products of 7 with 12 a single isomer [8d-A with (13'S,17'R,2,3,4-pS) configuration] was formed with ≥98% selectivity and isolated in 95% yield Treatment of the complexes 8 in tetrahydrofuran with water and pyridine N-oxide very effectively removed both transition metals with the formation of the corresponding β,γ-unsaturated e-hydroxy carboxylic acids The overall reaction sequence has thus converted the steroid ketone 12 very selectively to 5-[3-methoxy-17β-hydroxyestra-1,3,5(10)-trien-17α-yl]-(E)-pent-3-enoic acid (10d)

Martin Berlekamp

Papers

Monitoring the electronic features of rigid C1-bridged Group 4 ansa-metallocenes by using the dynamic and structural properties of their s-cis-η4-butadiene complexes

A Template Synthesis of Stable Conjugated Primary Enamines from Ketones, Nitriles, and Butadiene

Syntheses of substituted 6-hydroxyhexenoic acids and related tetrahydrofuran systems by metallocene-template directed 1,4-selective coupling of 1,3-butadiene with carbonyl compounds

A group 4 metallocene template synthesis of β,γ‐unsaturated ε‐hydroxy carboxylic acids

Eine templatsynthese stabiler konjugierter primarer enamine aus ketonen, nitrilen und butadien