Tuning the metal–metal separation in pyrazolate-based dinuclear complexes by the length of chelating side arms ‡

1998 ◽  
pp. 207-214 ◽  
Author(s):  
Franc Meyer ◽  
Katja Heinze ◽  
Bernhard Nuber ◽  
Laszlo Zsolnai
Keyword(s):  
Dinuclear Complexes ◽  
Metal Separation ◽  
Metal Metal

First Examples of Homogeneous Catalytic Cyclotrimerization and Polymerization of Phenylacetylene and Copolymerization of Phenylacetylene and Norbonene with Dinuclear Complexes Containing Unbridged Metal-Metal Quadruple Bond

2003 ◽  
Vol 68 (6) ◽  
pp. 1094-1104 ◽  
Author(s):  
Konstantinos Mertis ◽  
Stavros Arbilias ◽  
Demos Argyris ◽  
Nikos Psaroudakis ◽  
Jiří Vohlídal ◽  
...  
Keyword(s):  
Dinuclear Complexes ◽  
Addition Reactions ◽  
Polymer Yield ◽  
Quadruple Bond ◽  
Metal Metal ◽  
Medium Activity ◽  
Copolymer Structure ◽  
Almost All ◽  
Ligand Addition ◽  
Low Activity

First examples of application of dinuclear complexes containing unbrigded metal-metal quadruple bond as catalysts in cyclotrimerization, oligomerization and polymerization of substituted acetylene are reported. The d4-d4 dinuclear complexes (Bu4N)2[Re2X8] (1) (1a, X = Cl; 1b, X = Br and 1c, X = I) show low activity and the complex [Mo2Cl4(MeOH)2(PPh3)2] (2) medium activity in cyclotrimerization and oligomerization of phenylacetylene (PA). In contrast, the tungsten-based d4-d4, complex Na4[W2Cl8] (3) exhibits high polymerization activity (polymer yield above 90%) and ca 75% cis-selectivity in tetrahydrofuran. The activity and cis-stereoselectivity of these single-component catalysts decrease in the order 3 >> 2 >> 1, which is proportional to the metal-metal quadruple bond propensity towards ligand addition reactions. Complex 3 induces metathesis polymerization of norbornene (NBE) to poly(cyclopentene-1,3-diylvinylene) with 82% cis-selectivity and copolymerization of PA and NBE to almost all-cis high-molecular-weight copolymer containing cyclopentene-1,3-diylvinylene units, which is free of longer sequences of both PA and NBE units. This suggests that also homopolymerization of PA with 3 proceeds by the metathesis mechanism and that the PA/NBE copolymer structure is close to the alternating one.

Redox-Chemie einfach arsenverbriickter Zweikernkomplexe ohne Metall-Metall-Bindung /Redox Chemistry of Singly Arsenic Bridged Dinuclear Complexes without Metal-Metal Bonds

1979 ◽  
Vol 34 (9) ◽  
pp. 1195-1198 ◽  
Author(s):  
Thomas Madach ◽  
Heinrich Vahrenkamp
Keyword(s):  
Metal Carbonyl ◽  
Chemical Oxidation ◽  
Redox Process ◽  
Dinuclear Complexes ◽  
Carbonyl Complexes ◽  
Metal Carbonyl Complexes ◽  
Metal Metal ◽  
Metal Metal Bonds ◽  
Electron Transfers ◽  
Metal Bonds

The oxidations and reductions of 27 singly arsenic bridged dinuclear metal carbonyl complexes were investigated. There are indications that the complexes as a whole are involved in the redox process. However, the expected one and two electron oxidations with concomitant formation of metal-metal bonds were not observed. Electrochemical electron transfers were irreversible. Chemical oxidation and reduction of a selected example resulted in a series of products originating from the primary fission of one metal-arsenic bond.

Binuclear Silver (I) Complex with Double Armed Diaza-Crown Ether Containing Short Metal-Metal Separation

1992 ◽  
Vol 21 (4) ◽  
pp. 699-702 ◽  
Author(s):  
Ken Hirotsu ◽  
Ikuko Miyahara ◽  
Taiichi Higuchi ◽  
Mitsuo Toda ◽  
Hiroshi Tsukube ◽  
...  
Keyword(s):  
Crown Ether ◽  
Metal Separation ◽  
Metal Metal

Palladium(ii)–palladium(ii) bonding in two open clamshell dinuclear complexes

2017 ◽  
Vol 41 (15) ◽  
pp. 7384-7391 ◽  
Author(s):  
Shanti G. Patra ◽  
Nirmal K. Shee ◽  
Michael G. B. Drew ◽  
Dipankar Datta
Keyword(s):  
Bond Order ◽  
Dinuclear Complexes ◽  
Metal Bond ◽  
Metal Metal

In two Pd(ii) dimers with Pd–Pd distance ≤3.26 Å, the metal–metal bond order is found to be zero.

Oxidative Abbaureaktionen des homonuklearen Cobalthydridclusters [(η5-Cp*)Co]3H4 / Oxidative Degradation Reactions of the Homonuclear Cobalt Hydride Cluster [(η5-Cp*)Co]3H4

1995 ◽  
Vol 50 (4) ◽  
pp. 448-459 ◽  
Author(s):  
Jörg J. Schneider ◽  
Richard Goddard ◽  
Carl Krüger
Keyword(s):  
Crystal Structures ◽  
Oxidative Degradation ◽  
Dinuclear Complexes ◽  
X Ray ◽  
X Ray Crystallography ◽  
Degradation Reactions ◽  
Mononuclear Complexes ◽  
Metal Metal ◽  
Inorganic Substrates ◽  
Cobalt Compounds

The homonuclear cobalt cluster [(η5-Cp*)Co]3H4 2 reacts with various organic and inorganic substrates with complete degradation of the cluster core to afford mainly mononuclear organometallic cobalt compounds. Thus, whereas reaction of the cluster with CO, NO or alkynes results in the retention of the Co3 ring, the cluster reacts with Br2, I2, I2/CO , I2/ P(C 2H5)3, CCl4, HCI3, (CH2)2Br2, Hacac, CH2Br2, (C6H5CO)OOC(CH3)3, HBF4, and BrCN to give mononuclear complexes or bridged dinuclear complexes without a metal-metal bond. In all cases formal oxidation of the metal center is observed. The crystal structures of six organocobalt complexes have been determined by X-ray crystallography.

Organic-inorganic hybrid materials from divalent metal cations and expanded N,N′-donor linkers

2018 ◽  
Vol 233 (2) ◽  
pp. 97-111 ◽  
Author(s):  
Mansoureh Zahedi ◽  
Behrouz Shaabani ◽  
Ulli Englert ◽  
Jan van Leusen
Keyword(s):  
Layer Structure ◽  
Metal Cations ◽  
Antiferromagnetic Coupling ◽  
Reaction Products ◽  
Ancillary Ligands ◽  
Orbital Interactions ◽  
Metal Separation ◽  
Metal Metal ◽  
Secondary Building Units ◽  
Simple Chain

AbstractThe rod-shaped linker (E,E)-N,N′-(3,3′-dimethyl-4,4′-biphenyldiyl)bis[1-(3-pyridinyl)methanimine] (L) is exploited for the first time in the synthesis of extended structures. Four new coordination polymers of composition {[ZnL(OAc)2]·EtOH}n(1), {[CdL(OAc)2]·MeOH}n(2), {[Cu2L(OAc)4]·CH2Cl2}n(3) and [MnL(N3)2]n(4) have been structurally characterized. The metal cations and the anionic ancillary ligands play pivotal roles for the topology of these compounds. In the crystalline reaction products of Zn(II), Cd(II) and Cu(II) acetate with the organic linker, the acetate anions connects two neighboring cations to dinuclear [M2(OAc)4] subunits. These secondary building units are further crosslinked by the N,N′-donor ligand, either perpendicular to the acetato bridges, leading to a ladder-like ribbon for1and2, or in the direction of the metal···metal separation, resulting in a simple chain in the case of3. Instead of dinuclear secondary building units, a different topology results from reaction of the N,N′ linker with Mn(ClO4)2in the presence of azide anions: 1,3 bridging by the N3−groups leads to infinite chains. These are crosslinked by L in perpendicular direction, and the layer structure4is obtained. Natural bond orbital (NBO) analyses revealed information on the basis of orbital interactions about the coordination environments of the metal ions. Thermogravimetric measurements indicate the highest thermal stability for2. Strong antiferromagnetic coupling within the dinuclear subunits of3is observed as a consequence of superexchangeviathe acetato bridges.

Untersuchungen zur Existenz der Radikale Cp(CO)3M (M = Cr, Mo, W) / Investigations on the Existence of the Radicals Cp(CO)3M (M = Cr, Mo, W)

1979 ◽  
Vol 34 (4) ◽  
pp. 573-578 ◽  
Author(s):  
Thomas Madach ◽  
Heinrich Vahrenkamp
Keyword(s):  
Pure State ◽  
Reductive Cleavage ◽  
Electrochemical Measurements ◽  
Dinuclear Complexes ◽  
Metal Metal ◽  
Redistribution Reactions ◽  
First Time ◽  
Electrochemical Potentials

AbstractThe mutual interconversions of the species Cp(CO)3M- (2), Cp(CO)3M-M′(CO)3Cp (1), and Cp(CO)3M (3), (M,M′ = Cr, Mo, W) were investigated. Of the mixed dinuclear complexes 1, the Cr-Mo and Cr-W compounds were prepared for the first time, and the Mo-W compound was shown not to exist in a pure state. The Mo and W radicals 3, in contrast to the corresponding Cr radical, are not stable in measurable quantities in solution. Electrochemical measurements as well as simple redox and redistribution reactions, however, prove their ready formation and existence under normal conditions. There is a good correlation between the energies of the σ-σ* transitions of the metal-metal bonded dimers (1) and the electrochemical potentials for their reductive cleavage.

scholarly journals Crystal and solution structures of calcium complexes relevant to problematic waste disposal: calcium gluconate and calcium isosaccharinate

2018 ◽  
Vol 74 (6) ◽  
pp. 598-609 ◽  
Author(s):  
V. Bugris ◽  
Cs. Dudás ◽  
B. Kutus ◽  
V. Harmat ◽  
K. Csankó ◽  
...  
Keyword(s):  
Crystal Structure ◽  
X Ray Diffraction ◽  
Solution Structures ◽  
Single Crystal Structures ◽  
Metal Separation ◽  
Metal Metal ◽  
Structure Determinations ◽  
Modelling Studies ◽  
Calcium Complexes ◽  
Intramolecular Hydrogen

The single-crystal structures of calcium D-gluconate and calcium α-D-isosaccharinate have been determined using X-ray diffraction at 100 K. Surprisingly, given its significance in industrial and medical applications, the structure of calcium D-gluconate has not previously been reported. Unexpectedly, the gluconate crystal structure comprises coordination polymers. Unusually, the calcium coordination number is nine. Adjacent metal centres are linked by three μ-oxo bridges, with a metal–metal separation of 3.7312 (2) Å. One of the gluconate ligands contradicts a suggestion from 1974 that a straight chain conformation is associated with an intramolecular hydrogen bond. This ligand binds to three adjacent metal centres. The use of synchrotron radiation provided an improved crystal structure with respect to that previously reported for the isosaccharinate complex, allowing the location of the hydroxy hydrogen sites to be elucidated. In contrast to the gluconate structure, there are no μ-oxo bridges in the isosaccharinate coordination polymer and the isosaccharinate bridging coordination is such that the distance between adjacent metal centres, each of which is eight-coordinate, is 6.7573 (4) Å. Complementing the crystal structure determinations, modelling studies of the geometries and coordination modes for the aqueous [CaGluc]+ and [CaIsa]+ complexes are presented and discussed.

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