Klaus R. Pörschke

Elektronendichte-Verteilungen in metallorganischen Verbindungen. Wechselnde Struktur- und Bindungsverhältnisse in dimeren metallorganischen Nickel-Hydriden mit Ionenpaar-Beziehungen zu den Hauptgruppen-Metallen Natrium und Lithium

The compounds [[(C 2 H 4 ) 2 Ni] 2 H][Na(TMEDA) 2 ] (I) and [[(C 2 H 4 ) 2 Ni] 2 H][Li(CH 3 2 NCH 2 CH 2 N(CH 3 ) CH 2 CH 2 N(CH 3 2 ] (II) have been investigated by high resolution X-ray techniques. Compound I is found to exist as distinct ions which are well-separated in the unit cell, while II shows an ion pair contact between the lithium ion part and one nickel atom, one ethene group, and the hydride in the anion. This latter interaction has little effect on the geometry of the anion, which is similar in both compounds. Each nickel atom is surrounded by a trigonal-planar coordination geometry comprising two ethene groups and the bridging hydrige. The NiHNi bridge is non-linear and the angle at the hydrogen atom is 131 and 111°, respectively. The unusual geometry adopted by the anion is explained in terms of an interaction between the two nickel atoms involving the empty p -orbital on one metal with the filled d -orbitals on the other. The bonding situation obtained from semi-empirical molecular orbital calculations is in accord with the observed electron density distributions.

Zur Lewisacidität von Nickel(0): VII. Alkalimetall-μ3-hydrido-tetrakis(ethen)diniccolat(0)-Komplexe: (pmdta) Li(μ3-H)Ni2(C2H4)4 und (pmdta)Na(μ3-H)Ni2(C2H4)4

Abstract Ni(C 2 H 4 ) 3 reacts with alkalimetal hydridoaluminates or -gallates M A HAl/GaR 3 and M A H 2 AlR 2 (R= alkyl) in ether/pmdta at temperatures between −70 and −20°C to yield the ion pair complexes (pmdta)M A (μ 3 -H)Ni:(C 2 H 4 ) 4 (M A = Li ( 2a ), Na ( 2b )). According to their structure and chemical properties, 2a,b can be regarded as model compounds for the nickel(O) induced addition of alkalimetal hydrides to alkenes.

Neue Bis(phosphan)-nickel(0)-alkin-Komplexe /New Bis(phosphane)-nickel(0)-alkyne Complexes

Abstract (Me3P)2Ni(C2H4) (5) and (dmpe) 2Ni2(C2H4)3 (6) react with various alkynes including ethyne (acetylene) and 1-alkynes to form the crystalline compounds (Me3P)2Ni(C2RR′), (dmpe)Ni(C2RR′), and (dmpe)2Ni2(C2R2)2 (R.R′ = H, Me, Ph). Structural assignments were made on the basis of 1H, 13C, and 31P NMR data. The crystal and molecular structure of (dmpe)Ni(C2Ph2) (17) has been determined by X-ray crystallography.

Bis(dimethyIphosphino)methan-Nickel(0)-Komplexe / Bis(dimethylphosphino)methane-Nickel(0) Complexes

Abstract The reaction of tris(ethene)nickel(0) with stoichiometric amounts of bis(dimethylphos-phino)methane (dmpm) in ether at low temperature affords the yellow crystalline, dinuclear complexes (dmpm)Ni2(C2H4)4 (1) and (dmpm)2Ni2(C2H4)2 (2). 2 reacts with ethyne to yield (dmpm)2Ni2(C2H2)2 (3). When 2 is treated with CO at -40 °C the primary product is (dmpm)2Ni2(CO)2(μ-CO) (4). At 20 °C 4 is converted by additional CO into (dmpm)2Ni2(CO)4 (5), which has already been characterized as the reaction product of Ni(CO) 4 with dmpm. In compounds 1-5 the bidentate dmpm acts as a bridging and not as a chelating ligand. The structures of complexes 1-4 were assigned on the basis of their 13C and 31P NMR spectra.

Synthese und Struktur von Ni(2,6-iPr2C6H3N = CH – CH =NC6H3-2,6-iPr2)2. Synthesis and Structure of Ni(2,6-iPr2C6H3N=CH–CH = NC6H3-2,6-iPr2)2

Ni(cdt)** reacts with two equivalents of the sterically highly demanding 1,4-diazadiene 2,6-iPr2C6H3N =CH –CH =NC6H3-2,6-iPr, to yield the red-brown, crystalline title compound Ni(2,6-iPr2Ph-dad)2 (3). The existence of this compound was previously uncertain. 1H and 13C NMR, MS, and UV/VIS spectra of 3 are reported. The X-ray structure analysis of 3 revealed a strongly distorted tetrahedral coordination of the nickel center with a dihedral angle of 51 between the planes of the chelate rings and mean bond lengths Ni-Ν 1.965(4) Å and N=CH 1.308(5) Å. The poorly soluble compound appears to be rather unreactive because of the bulk of the ligands.

Tris(phosphan)-Nickel(0)-Ethen-Komplexe (dmpe)(PR3)Ni(C2H4). Molekülstruktur des (dmpe)(PØ3 )Ni(C2H4)/ Tris(phosphane)-nickel(0)-ethene Complexes (dmpe)(PR3)Ni(C2H4). Molecular Structure of (dmpe)(PO3)Ni(C2H4)

Abstract Synthesis and properties of tris(phosphane)(ethene)nickel(0) complexes (dmpe)(PR3)Ni(C2H4) (R = CH3(4), c-C6H11(5), and C6H5 (6)) are reported. In solution. 4-6 are thermolabile and undergo ligand exchange reactions affording tetrakis(phosphane)nickel(0 ) and bis(phosphane)- (ethene)nickel(0) complexes. 1H, 13C, and 31P NMR data of 4-6 confirm the tetrahedral geometry around nickel. For 6 , the crystal and molecular structure has been determined by X-ray crystallography.

Zweikernige Bis(dimethylphosphino)ethan-Nickel(0)-Komplexe (dmpe)1+nNi2(C2H4)4-n (n = 0, 1, 2) und (dmpe)4Ni2

Abstract Reaction of tris(ethene)nickel(0) with dmpe at low temperature affords the crystalline compounds (dmpe)Ni2(C2H4)4 (6), (dmpe)2Ni2(C2H4)3 (7), and (dmpe)3Ni2(C2H4)2 (8), depending on the stoichiometries employed. In 7 and 8 , nickel is tetrahedrally coordinated by ethene and three phosphorus ligands. In addition, (dmpe)4Ni2 (9) has been obtained with excess dmpe at 20 °C. Structural assignments were made on the basis of NMR spectra.