Eckhard Dinjus

Aktivierung von kohlendioxid an übergangsmetallzentren: Metallaringschluss mit dicyclopentadien am elektronenreichen nickel(0)-komplexrumpf als topo- und stereoselektive reaktion

Abstract CO 2 reacts with dicyclopentadiene (dcp) at the complex moiety (bipy)Ni 0 to form a five-membered nickelacycle as the result of a topo- and stereo-selective coupling reaction (reaction of the norbornene part, exo position). X-Ray analysis of the compound shows a planar configuration around the central atom with a NiC σ-bond length of 1.929 A and a monodentate carboxylato group (NiO distance: 1.845 A). The structure of the nickelacycle is compared with those of similar compounds formed by oxidative coupling of CH 3 CHO or PhCHNPh with CO 2 at electron-rich nickel(0) moieties. Relations between structure and reactivity are investigated.

Metallacyclen aus CO2 und dimethylbutadien am komplexrumpf (L)Ni0: Struktur und reaktivität als funktion der neutralliganden L

Abstract (L) Ni(CH 2 C(CH 3 )C(CH 3 )CH 2 COO) can be synthesized either by the oxidative coupling of CO 2 and diene at the complex moiety (L)Ni, or by the exchange of neutral ligands in metallacycle I (L = N, N ′-tetramethylene diamine (TMED)). X-ray analyses of the compounds with L = Ph 3 P and Cy 3 P show that the C 5 O chains are bonded similarly, with an η 3 -allyl- and a monodentate carboxylate group at the ends of the chains. Thermal investigations and reactions with π-acceptor ligands were carried out as a function of the neutral ligands L. The reaction of I with π-acidic 1,4-diazadienes leads to 3,4-dimethyl-penta(2,4)dienecarboxylic acid and simulates a partial step of a possible catalytic cycle: oxidative coupling - reductive elimination under H-shift.

Aktivierung von Kohlendioxid an Übergangsmetallzentren: Kristall- und molekulstruktur von 2,2′-dipyridyl-nickela-5-methyl-2,4-dioxolan-3-on, einem Kopplungsprodukt von Kohlendioxid und Acetaldehyd am Zentralatom Nickel (0)

Abstract Carbon dioxide reacts with acetaldehyde in the presence of dipyNi(COD) (COD = 1,5-Cyclooctadiene) to yield a red organonickel(II) compound as the result of oxidative coupling of both hetero-π-systems at the central metal. The crystal and molecular structures have been determined by X-ray analysis. The complex is monoclinic (space group P21/n; cell data: a 6.004(2), b 18.012(7), c 11.266(5) », β 96.02(4)°, R = 0.10) with 4 molecules in the unit cell. The structure was solved by the heavy atom technique. The complex has a planar configuration at the central atom and contains a five-membered metallacycle with a metal—C and a metal—O σ-bond. Many other aliphatic aldehydes react with carbon dioxide to yield the same type of complex.

Aktivierung von kohlendioxid an übergangsmetallzentren: nickela(II)-heterocyclen aus kohlendioxid und azaolefinen am elektronenreichen nickel(0)-komplexrumpf

Abstract The oxidative coupling of carbon dioxide and azaolefins (RCHNR′) at electron-rich nickel(0) centers (e.g. bipyNi 0 and (TMED)Ni 0 ) gives nickela(II) five-membered heterocycles with NiC and NiOσ-bonds. The crystal and molecular structure of a typical compound with PhCHNPh as an azaolefine and (TMED)Ni as complex moiety has been determined (space group Pna 2 1 ; cell data a 13.578, b 14.996, c 9.643 A; R = 0.038 with 4 molecules in the unit cell). The structure was solved by the heavy atom technique. The planar metallacycles are the first complexes with carbaminic acid dianions as bidentate ligands. Some reactions of the complexes are described.

2,2′-dipyridyl-1,5-cyclooctadiennickel(0): kristall-und molekülstruktur

Abstract 2,2′-Dipyridyl-1,5-cyclooctadienenickel(0) is monoclinic (space group P 2 1 / c ) with four molecules in the unit cell. The complex has tetrahedral configuration at the central atom with symmetrical bonds to the double bonds of the cycloolefinic ligand and remarkable short NiC bonds (2.052 A). The NiN distances are 1.940(4) and 1.936(4) A. The conformation of the 1,5-cyclooctadiene is a twist boat form. The R -value of the structure determination is 0.048.

Aktivierung von CO2 an Übergangsmetallzentren: Struktur und Reaktivität eines C-C-Kopplungsproduktes von CO2 und 2.3-Dimethylbutadien am elektronenreichen Nickel(O) / Activation of CO2 at Transition Metal Centers: Structure and Reactivity of a C-C-Coupling Product of CO2 and 2,3-Dimethylbutadiene at Electron-Rich Nickel(O)

Carbon dioxide reacts with 2,3-dimethylbutadiene and bis-cyclooctadiene(1,5)-nickel(O) in the presence of N,N′-tetramethyl-ethylendiamine (tmeda) to form [(3,4,5-η3)-3,4-dimethyl-3-pentenylato](N,N′-tetramethyl-ethylendiamine)-nickel(II) as the product of the oxidative coupling of CO2 and the diene. The deep red complex crystallizes in the rhombic space group Pbca. The structure was determined by an X-ray analysis. The monodendate carboxylate group, the π-allyl system and a N-atom of tmeda form a planar coordination sphere around the central atom. The distance between Ni and the second N-atom of tmeda is very long (2.314 Å). Reaction of the complex with R−X (R: H, CH3) yield 3-unsaturated carboxylic acids; tmeda can be substituted by 2,2′-bipyridine.

Phosphinoalkylnitrile: Synthese und Koordinationsverhalten an Palladiumzentren / Phosphinoalkylnitnles: Synthesis and Coordination Behaviour at Palladium Centres

Phosphinoalkylnitriles R2P-(CH2)n-CN {R = isopropyl (ipr), phenyl (ph), cyclohexyl (chex), n = 3, 6, 10} have been prepared starting from the corresponding secondary phosphines in an easy three step synthesis. All new compounds were characterized by their 1H -, 13C and 31P NMR data. Some of these new P, N ligands were used to prepare complexes [{R2P- (CH2)n-CN}2PdCl2] which were also identified by their NMR data. In addition the crystal structures of three derivatives, [{ipr2P-(CH2)3-CN}2PdCl2] 7a, [{ph2P-(CH2)3-CN}2PdCl2) 7b and [{ph2P-(CH2)6-CN}2PdCl2] 8b were determined by X-ray analysis. The coordination mode of the phosphinoalkylnitriles in these complexes was found to be P-bonded resulting in a trans configuration. Palladium catalysts with 5a as ligand show high activies in the co-oligomerization of butadiene and carbon dioxide. The δ-lactone 11a is formed under very mild conditions.