Reinald Fischer

A key step in the formation of acrylic acid from CO2 and ethylene: the transformation of a nickelalactone into a nickel-acrylate complex

The reaction of a nickelalactone with dppm, resulting in the formation of a stable binuclear Ni(I) complex with an acrylate, a Ph2P- and a dppm bridge, models a key step in the formation of acrylic acid from CO2 and ethylene.

Zirkoniumorganische chemie mit anorganischen donorliganden N,N′-Bis(trimethylsilyl) benzamidinat (Siam) in verbindungen des typs (Siam)2ZrX2 (X = Methyl, Benzyl, Allyl, Chlorid oder Iodid) und (Siam)3ZrX (X = Chlorid)

Abstract Organometallic compounds of the type (Siam) 2 ZrX 2 (Siam = N , N ′-bis(trimethylsilyl)benzamidinat; X = methyl, benzyl or allyl) have been synthesized by reaction of (Siam) 2 ZrCl 2 and Grignard reagents. The structures of (Siam) 2 ZrX 2 (X = Cl, I, CH 3 or CH 2 C 6 H 5 ) and (Siam) 3 ZrCl have been investigated by X-ray crystal structure analysis. (Siam) 3 ZrCl shows a capped octahedral structure with the coordination number 7 at the zirconium. (Siam) 2 ZrX 2 compounds have distorted octahedral structures and the ligands occupy cis -positions. The distortion depends on the bulkiness of the ligand X. The systems (Siam) 2 ZrCl 2 -methylalumoxan (MAO) and (Siam) 3 ZrClMAO polymerize at 30°C reactive olefins such as ethylene or norbornene. Less reactive olefins (e.g. propene) can be reacted with (Siam)ZrCl 3 -MAO to yield oligomers and polymers. The same catalytic system is able to convert 1,5-hexadiene selectively under formation of methylene-cyclopentane.

Nickelalactone als Synthesebausteine: Sonochemische und Bimetallaktivierung der Kreuzkopplungsreaktion mit Alkyl-halogeniden

Abstract Nickelalactones with five- and six-membered chelate ring structures can be synthesized in a simple one-pot reaction, starting from Ni(acac) 2 , bipy, Et 3 Al and cyclic anhydrides. In the presence of MnI 2 and by activation with ultrasound they react selectively with alkyl iodides in cross coupling reactions. The reason for the activating effect of MnI 2 is the formation of bimetallic complexes. Many reactive functional groups ( e.g. COOR, CHO, CN) can be tolerated. Therefore the cross coupling reaction is of preparative value in the synthesis of functionalized carboxylic acids.

Complexes of the bis(trimethylsiyl)-benzamidinato ligand ‘siam’: synthesis and X-ray structures of (siam)2M, (siam) (siamH) MX (M=Ni, Pd), (siam)2MnI and (siam)ReO3, and their reactivity towards CO2

Complexes with the bis(trimethylsilyl)-benzamidinato ligand ‘ siam ’ of the type ( siam ) 2 M (M=Ni ( 2 ). Pd ( 3 ). ( siam ) ( siam H)NiBr ( 4a ), ( siam ) ( siam )( siam H)PdCl ( 4b ) and ( siam ) 2 MnI ( 5 ) were prepared by reaction of ( siam ) 2 Mg(thf) 2 ( 1 ) with the corresponding metal halides and addition of water or iodine, respectively. The reaction of ( siam ) 2 Zn with Re 2 O 7 yielded ( siam )ReO, ( 6 ). X-ray analysis of 1–6 revealed that siam acts as a bidentate ligand forming four-membered chelated rings in all complexes. In 2 four nitrogen atoms show a distorted tetrahedron; in contrast, 3, 4a and 4b are square planar complexes. In both 4a and 4b siam H is coordinated as a monodentate ligand The Mn(III) complex 5 exhibits a trigonal bipyramidal coordination of the four amidinato nitrogens and the iodo ligand, which occupies an equatorial position. The Re(VII) complex 6 shows an irregular trigonal bipyramidal coordination. In all compounds the bond lengths and angles in the amidanato ligand are comparable and exhibit typical values. The reaction of 2 with excess CO 2 gave a green dimeric complex 7 in which one Ni(II) centre is octahedral and the other is square pyramidal coordinated. X-ray analysis revealed that 5 mol CO 2 per 2 mol nickel are inserted in NSi bonds forming new types of tridentate bridging ligands which contain N-COOSiMe 3 groups.

A Dilithium 1,4‐Butanediide with a Chlorine‐Centered Li12 Icosahedral Structure

First organolithium compounds were prepared in the middle of the 19th century, and today they continue to play a key role in organometallic chemistry for many reasons such as commercial availability, straightforward preparative procedures, and a broad application spectrum. To understand and tune the properties of organolithium derivatives, their structures have been investigated in the solid state as well as in solution. The structural diversity of organolithium derivatives is a consequence of aggregation often based on triangle-based Lin polyhedrons and platonic bodies. The triangular faces often are capped by carbanions, thus leading to short Li Li contacts. Small aggregation degrees can be achieved with bulky substituents and by addition of Lewis bases L such as ethers or amines. Depending on the coligand L and on the bulkiness of R, the following structures are the most common: Li(L)nR (monomeric molecules), Li(L)n + (R-Li-R) (lithium lithiates), [Li(L)2(m-R)]2 (with Li2C2 rings), [Li(m3-R)]4 (with Li4 tetrahedrons), and [Li(m3-R)]6 (with distorted Li6 octahedrons). Higher nuclearity and aggregation degrees are rather seldom, and usually similar structural features are observed such as (LiX)2 and (LiX)3 rings that dimerize to cubes or hexagonal prisms or aggregate to ladder-like structures. Whereas in molecular organolithium chemistry larger lithium cages are to date unknown, icosahedral cages that contain an interstitial lithium atom are known for zero-valent lithium. These lithium(0)-centered Li13 icosahedra were found in intermetallic phases such as Li18.9Na8.3Ba15.3 [5] or the subnitride Li80Ba39N9. [6] Interpenetrating lithium icosahedra Li19 formed during the crystallization of Li33.3Ba13.1Ca3 [5] and of binary Li44Ba19. [7] Icosahedra seem to be typical in Li-rich intermetallic compounds. In these lithium(0) clusters, Li Li separations between 287 and 344 pm were found. These results suggest that icosahedral cages of lithium(I) cations should also be feasible. To overcome electrostatic repulsion between lithium cations, the lithium cage has to contain an anion X , which is surrounded by the Li ions (Figure 1). However, the presence of halide ions in many lithium organometallic compounds does not lead to halide-centered lithium cages, but the halide ion is able to replace alkyl groups which cap Li3 faces of lithium polyhedrons. This substitution leads to less reactive organolithium compounds, for example [Li4Me4 nXn] with a central Li4 tetrahedron. Therefore, the concept had to be expanded, and as an outer organic clamp a 1,w-butanediide ion was used. The reaction of lithium sand with 1,4-dichlorobutane in diethyl ether led to a clear solution which contained several chemically different 1,4-butanediide anions, as determined by H and C NMR spectroscopy. Cooling of the reaction mixture led to the precipitation of single crystals. However, a high-quality structure determination failed owing to heavy disordering of the cation. Nevertheless, the structure determination suggested a solvent-separated ion pair [Li(Et2O)4] [Li12{m3,m3-(CH2)4}6(@-X)] (1), which showed a Li12 icosahedron centered around an anion X . The nature of X was not absolutely clear; the electron density pointed towards a hydride anion (which can be explained by b-H abstraction), but a chloride also seemed to offer a possible solution. To investigate the stability of these [Li12{m3,m3-(CH2)4}6(@X)] cages towards Lewis bases and to obtain less soluble compounds that crystallize without disordering, twoand three-dentate Lewis bases were added to the reaction solutions. The addition of the two-dentate Lewis bases 1,2dimethoxyethane (dme) and 1,2-bis(dimethylamino)ethane (tmeda) only led to ligand exchange reactions at the cation, yielding [Li(dme)2] [Li12{m3,m3-(CH2)4}6(@-Cl)] (2) and [Li(tmeda)2] [Li12{m3,m3-(CH2)4}6(@-Cl)] (3), respectively (Scheme 1). These compounds displayed similar disorder problems as observed in 1, because both of these complexes crystallized in the same space group Fd 3 with the cations on crystallographic C3 axes, which leads to severe disordering of the complex cations. To meet the crystallographically specified symmetry, thus resolving the disorder, a cyclic base with C3 symmetry, 1,3,5-trimethyl-1,3,5-triazinane (tmta), was chosen. In this way, the complex [Li(tmta)2] [Li12{m3,m3-(CH2)4}6(@-Cl)] (4) could be isolated in high yield, and its crystal structure showed no signs of disorder. The molecular structure of 4 and its numbering scheme is shown in Figure 2. The cation of this solvent-separated ion Figure 1. An anioncentered lithium icosahedron.

Some applications of thermal analysis to the coordination chemistry

The behaviour of complexes of the type MeD2I2 (Me=Co,D = acetylacetone or benzoylacetone,I = imidazole and derivatives in the course of the stepwise thermal degradation is different. In the case ofD = acetylacetone in the first step acetylacetone is split off. At D = benzoylacetone the decomposition starts with the partial elimination of the heterocyclic ligands.InΒ-position unsubstituted nickelacyclic complexes from type (bipy)Ni(CH2CH2CH2COO) decompose by a reductive elimination and separating of CO2 forming a ‘(bipy)Ni’-intermediate. A single reductive decoupling is hindered by blocking up theΒ-position.Opposite to the high thermal stability of the trimesityl aluminium the intermediates Almes2Cl and AlmesCl2 show with decreasing amounts of mesityl groups and increasing content of halogene, respectively, a significant decreasing thermal stability.The thermal degradation of nickelchelates of alkylsubstituted chinolin-8-ol starts with the dehydration followed by a different separation of the ligands as a function of the chain-length and the position of the substituents of the ligands.ZusammenfassungDas Zersetzung Verhalten der Komplexverbindungen vom Typ C0D2I2 (P = acetylaceton, Benzoylaceton;I = Imidazol oder Derivate) erfolgt stufenweise. Im Falle vonD = Acetylaceton erfolgt zuerst eine Eliminierung von Acetylaceton wärend beiD = Benzoylaceton zuerst ein Heteroligand eine Abspaltung erfährt.Bei einer unsubstituiertenΒ-Position von Nickelacyclen des Typs (bipy)Ni(CH2CH2CH2COO) erfolgt eine thermisch induzierteΒ-Hydrideliminierung unter Ringspaltung und Freisetzung von CO2.Im Gegensatz zur hohen thermischen Stabilität des Trimesityl Aluminium erfahren die Zwischenverbindungen Almes2Cl und AlmesCl2 mit abnehmenden Mesityl- bzw. zunehmenden Chlorgehalt einen wessentlich früheren thermischen Zerfall. Bei zunehmenden Kovalenzgrad ist hier ein Einfluss der veränderten Polarisation anzunehmen.Der thermische Abbau der prinzipiell wasserhaltig kristallisierenden Nickelchelate von alkylsubstituierten Chinolin-8-ol beginnt jeweils mit der Dehydratisierung. In Abhängigkeit von der Kettenlänge und der Position der Substitution am Chinolin schliesst sich der thermische Abbau der Chelatliganden ein- bzw. mehrstufig an.

Beiträge zur chemie organometallischer metallacyclischer nebengruppemetallverbindungen XI. Synthese und charakterisierung von und seine umsetzung mit CH3I und einem C22-steroidiodid

Abstract reacts with 2 mol of CO 2 to form a seven-membered cyclic nickel compound of the type I . No ring contraction has been observed in this complex. Acidolysis of the product of the cross-coupling reaction of I with CH 3 I gives caproic acid. The reaction of I with the C 22 -steroid iodid V can be used for the formation of the C 27 -steroid carboxylic acid VI .

Unexpected Reaction of 2,2′‐Bipyridyl‐cycloocta‐1,5‐diene‐nickel(0) with Acetone and Dioxygen

The reaction of (bipy)Ni(cod) (1) (bipy = 2,2′-bipyridyl, cod = cycloocta-1,5-diene) with dioxygen and acetone at −20°C affords (bipy)Ni(C9H16O3) (2) (C9H16O32— = 2,4,6,6-tetramethyl-tetrahydropyran-2,4-diolate), which has been characterized by NMR, MS and an X-ray crystal structure determination. Acidolysis of compound 2 with two equivalents of acetyl acetone (Hacac) yields (bipy)Ni(acac)2 and C9H18O3 (3) (2,4,6,6-tetramethyl-tetrahydropyran-2,4-diol), a cyclic trimer of acetone.