Günther Wilke

Organo transition metal compounds as intermediates in homogeneous catalytic reactions

Abstract Metallocycles occur in many cases as intermediates in processes which are catalyzed by transition metal complexes in the homogeneous phase. Frequently, it proved possible to isolate metallocycle complexes from catalytic experiments in crystalline form and to determine their structures by NMR-sepctroscopy as well as x-ray analysis. 3,4,5,7,9,11,12,13,14-membered metallocycles have been shown to be important in catalytic reactions involving alkynes, alkenes and 1,3-dienes. Isolated binuclear metallocycles suggest pathways for catalytic reactions involving two metal atoms.

Transition metal allyls : IV. The (η3-allyl)2M complexes of nickel, palladium and platinum: reaction with tertiary phosphines

Abstract A series of 1 : 1 adducts have been prepared by treating the bis-η3-allyl complexes of nickel, palladium and platinum with tertiary phosphines. Investigations of their structure in solution as well as in the crystal have shown that both 18-electron (η3-allyl)2ML complexes as well as 16-electron (η1-allyl)-(η3-allyl)ML complexes may be formed.

π-Allylnickel Intermediates in Organic Synthesis

Publisher Summary Isolation of the intermediate π-allylnickel complexes and the discovery that these react with activated olefins and organic halides in general have led to a considerable increase in the scope of the reaction. The coupling of an allylic halide which can exist as a cis or trans form is, in many cases, stereochemically nonspecific. This interconversion of the allyl groups may be explained by a 1,3-rearrangement through a σ-allylnickel complex. Dihalides undergo disubstitution, and coupling occurs at the primary rather than at the more substituted end of the allyl group. The reaction may be taken a step further using a mixture of acetylene and carbon monoxide. The products are particularly sensitive to reactant concentration, solvent, and available moisture, and can be visualized as the growth of an organic chain, bonded to a nickel atom, by the successive insertion of CO or acetylene molecules, which is interrupted at various points by the uptake of a proton or hydroxyl ion or by decomposition of the intermediate.

Transition metal allyls ☆: III. The (η3-allyl)2M complexes of nickel, palladium and platinum: structural considerations

Abstract The structures of a series of (η 3 -allyl) 2 M complexes of nickel, palladium and platinum have been investigated with the help of 13 C NMR, 1 H NMR and Raman spectroscopy. The crystal structure of (η 3 -cyclooctatrienyl) 2 Ni has been determined by X-ray methods; the two nickel-bonded η 3 -allyl groups are mutually trans .

Übergangsmetallkomplexe : III. Über zirkonorganische komplexe mit cyclooctatetraen als ligand☆

Abstract The insoluble complex (COT) 2 Zr(I) may be prepared by reduction of Zr(OR) 4 with Al(C 2 H 5 ) 3 in the presence of cyclooctatetraene (COT) or by treating tetraallylzirconium (II) with COT. I dissolves in (C 2 H 5 ) 2 AlH readily to give the 1,1- and 1,2-adducts (COT) 2 Zr[HAl(C 2 H 5 ) 2 ] 1 or 2 (IV) and (III). The reaction of I with gaseous HCl gives COTZrCl 2 (VII), which reacts with RMgX to give organometallic derivatives of the type COTZrR 2 (R = CH 3 (X), C 2 H 5 (XII), allyl (XIII) and crotyl (XVIII)). The reaction of Zr(OR) 4 , COT and (C 2 H 5 ) 2 AlH gives COTZrH 2 (XIX). XIII dimerizes butadiene catalytically and stereospecifically to 1,3- trans ,6- cis -octatriene (XIV). The crystalline complex COTZrC 8 H 12 (XVII) has been isolated as an intermediate from the dimerization reaction. In XVII a C 8 -chain is bonded through ? the zirconium. The constitution of III, X, XII, XIII, XVII and XVIII have been confirmed by their 1 H NMR spectra.

Ir- und 1H-NMR-spektroskopische untersuchungen an zirkon und hafniumallylen : I. Übergangsmetallallyle

Abstract A general scheme, utilizing both energetic and kinetic data, has been derived for the classification of allylmetals. On the basis of IR spectral data, three categories 1–3 may be formulated. These may be subdivided into a and b on the basis of their 1 H NMR spectra and hence 6 different types may be distinguished π-, σ-, π- and σ-dynamic or static. The spectra of allyl-zirconium and -hafnium compounds (MA 4 , COTMA 2 , COTMMet 2 , COTMCrot 2 , M = Zr, Hf; A = allyl; Met = methylallyl; Crot = crotyl; COT = cyclooctatetraene) are discussed and the compounds classified according to the above scheme.

Über primäre Reticuloendotheliosen des Gehirns

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Transition metal allyls. VI: The stoichiometric reaction of 1,3-dienes with ligand modified zerovalent-nickel systems

ende ~bergi~nge zu den b la s tomat6sen E r k r a n k u n g e n des cerebralen Gef~Bwandappara tes , dessen Elemente mi t ihreu plur ipot en ten Eigenschaf ten auch den Mut t e rboden dieser E r k r a n k u n g e n liefern.

tmeda-Nickel-Komplexe: III. (N,N,N′,N′-Tetramethylethylendiamin)-(dimethyl)nickel(II)

Abstract Butadiene and methyl substituted 1,3-dienes react with zerovalent-nickel-ligand complexes in a stoichiometric manner to give octadienediylnickel-ligand complexes. The structure, rearrangement and reactions with CO and P-donor ligands of these species have been studied with the help of 1 H and 13 C NMR spectroscopy. The results provide an insight into the mechanism of the nickel-catalysed cyclodimerization of 1,3-dienes.

Übergangsmetallkomplexe ☆ ☆☆: IV. CC-spaltung und-verknupfung in komplexgebundenem cyclooctatetraen, struktur und bestimmung der elektronen-deformationsdichte im μ-octatetraenyl-bis[(π-cyclopentadienyl)chrom] durch tieftemperature-röntgenbeugung (X—X)

Abstract (tmeda)Ni(acac) 2 reacts with the main group metal compounds (tmeda)Mg-(CH 3 ) 2 , (tmeda)&[;Al(CH 3 ) 3 &]; 2 , and (C 2 H 5 O)Al(CH 3 ) 2 at 0°C to give (tmeda)Ni-(CH 3 ) 2 ( 1 ), which can be isolated as fine yellow crystals in 50–80% yield. Complex 1 , which is the simplest dialkyl nickel(II) compound with a “hard” donor ligand, is surprisingly stable and decomposes only at 79°C. 1 is converted by bipy to (bipy)Ni(CH 3 ) 2 and by Me 2 PC 2 H 4 PMe 2 to (Me 2 PC 2 H 4 PMe 2 )Ni(CH 3 ) 2 . Upon reaction of 1 with strong π-acceptor molecules (acrylic acid methylester, methyl vinyl ketone, acrylonitrile, tetracyanoethene, tetrafluoroethene, maleic anhydride) reductive elimination of the methyl groups takes place to give the complexes (tmeda)Ni(π-ligand) n ( n = 1, 2) and ethane.