Nickel coordination polymers

The neutral three-dimensional nickel coordination polymer with 4,4 -bipyridine and 1,2,4,5-benzenetetracarboxylate was prepared by Wu and coworkers [206]... 

Bis[(dimethylisopropoxysilyl)methyl]zinc (74) has proven to be a valuable reagent in the nickel-catalysed cross-coupling reactions with alkenylsulfoximines, giving allylic silanes with complete retention of configuration. An X-ray crystal structure determination of 74 showed this compound to exist in the solid state as a coordination polymer (Figure 41). In 74, in addition to the two covalent Zn—C bonds [Zn—C(l) 1.953(7)... 

Under similar conditions, 2-D coordinated polymers of some other 1-alkyltetrazoles 31 were synthesized using copper(ll), iron(ll), and nickel(n) halides and nitrates <2002IC6468, 2002ICA(335)61, 2003M255, 2003ICA(350)57, 2003JCD3628>. In these complexes, halide and nitrate anions are included in the inner coordination sphere. 

Fig. 5 Some 2-D coordination polymers (a) nickel bis(imidazolate), containing neutral sheets of square planar metal centers,16 (b) a plan view of the europium isophthalate structure,17 showing nine-coordinate Eu3+, and (c) copper adipate,18 which consists of both chains and sheets, viewed along the chain axis. Gray spheres denote carbon, white hydrogen, blue nitrogen, red oxygen, and green nickel, with EuO, polyhedra in orange and CuOs square pyramids in blue.

Figure 34 Cross-linking of Ni(p,-SCN)2L2 n coordination polymer via carboxyl-carboxyl hydrogen bonds between isonicotinic acid ligands (L) to give a sheet structure which stacks providing channels that can accommodate polycyclic aromatic hydrocarbon guest molecules, here anthracene [80], Oxygen, nitrogen and key hydrogen atoms are shaded nickel thiocyanate polymer and anthracene guest molecules shown in wireframe style.

Helical coordination polymers containing large chiral cavities or charmels are interesting for stereospecific syntheses, separation of enantiomers and stereoselective catalysis. Crystals of 39 are obtained from a solution of nickel(II) acetate and benzoic acid in methanol which is covered with a solution of 4,4 -bipyridine in the presence of benzene or nitrobenzene [107]. Each helix turn contains three complex units and the chain consists of Ni(II) (with binding of benzoate) and the bipyridine. Because each helix is shifted against the next, large cavities are formed containing, for example, benzene or nitrobenzene. 

Experiment 7-7 Synthesis of the Three-Dimensional Coordination Polymer 40 from Nickel(II), Benzenetetracarboxylic Acid and 4,4 -Bipyridine (Section 7.3.2.1) [119]... 

As reported earlier [39-42] CS2 can be reacted to thiapendione, which can be converted into ethylenetetrathiolate (TT), by cleavage with strong chemical bases. Additionally, thiapendione can be "dimerized" to bis(l,3-dithiole-2-one)tetrathiafulvalene, which can be converted into tetrathiolatotetrathiafulvalene (TTF-TT), again by a cleavage reaction with strong bases. Both tetrathiolates react with transition metal ions, like nickel(II) or copper(II), to form coordination polymers which are remarkably inert, chemically as well as thermally [38]. The reactions, and their final products, are schematically summarized in Fig. 20. Fig. 21 shows a schematic picture of the possible coordination between different chains. 

Rubeanic acid, the diamide of dithio-oxalic acid, presents an equilibrium mixture with its tuatomeric (aci-) di-imido form as outlined on page 406. The aci-form combines with nickel, cobalt, and copper ions to give colored water-insoluble polynuclear coordination polymers. 

Another early coordination polymer was reported in 1944 by Jensen who proposed the linear product 4 from the chelation of nickel ions with rubeanate. ... 

Bis(xanthates) are a readily accessible class of bis(ligands), but surprisingly little research has been published about their coordination polymers with metals 3, 7). This could be due to the fact that thermal stability screening studies showed them to be inferior in this respect (i). A series of polymeric nickel bis(xanthates) have been prepared from reaction of bis(potassium xanthates) with nickel salts (7) (see Table X.3, p. 315). Only meager information about their properties has been published. 

Reactions that include proton transfer are a powerful tool for the mechanochemical synthesis of coordination polymers and MOFs. Particularly noteworthy are reactions of metal acetate precursors with organic acids, which result in the formation of coordination polymers, accompanied by the release of acetic acid. Such reactivity was observed, e.g., between hydrated nickel(II) acetate and acetylenedicarboxylic acid (H2adc), resulting in the formation of a hydrated 3-D coordination polymer... 

Opelt S, Turk S, Dietzsch E, Henschel A, Kaskel S, Klemm E. Hydrogen adsorption in a nickel based coordination polymer with open metal sites in the cyhndrical cavities of the desolvated framework. Catal... 

The thermally stable coordination polymers were prepared by the com-plexation of tetracarboxylic diimidates, such as pyromellic diimide (PMDI), with the salts of cobalt, nickel, copper, zinc, and mercury in DMF solution [43-46]. The linear coordination polymer of tetracarboxylic diimidate with zinc or mercury, is thermally stable above 550°C. Hojo et al. also reported the preparation and thermal stability of a series of aliphatic amine complexes of bivalent transition metals, such as cobalt, nickel, copper, zinc, and mercury, with tetracarboxylic acid diimidates [45]. 

Polymerization of alkynes by Ni" complexes produces a variety of products which depend on conditions and especially on the particular nickel complex used. If, for instance, O-donor ligands such as acetylacetone or salicaldehyde are employed in a solvent such as tetrahydrofuran or dioxan, 4 coordination sites are available and cyclotetramerization occurs to give mainly cyclo-octatetraene (cot). If a less-labile ligand such as PPhj is incorporated, the coordination sites required for tetramerization are not available and cyclic trimerization to benzene predominates (Fig. A). These syntheses are amenable to extensive variation and adaptation. Substituted ring systems can be obtained from the appropriately substituted alkynes while linear polymers can also be produced. 

Nickel and palladium react with a number of olefins other than ethylene, to afford a wide range of binary complexes. With styrene (11), Ni atoms react at 77 K to form tris(styrene)Ni(0), a red-brown solid that decomposes at -20 °C. The ability of nickel atoms to coordinate three olefins with a bulky phenyl substituent illustrates that the steric and electronic effects (54,141) responsible for the stability of a tris (planar) coordination are not sufficiently great to preclude formation of a tris complex rather than a bis (olefin) species as the highest-stoichiometry complex. In contrast to the nickel-atom reaction, chromium atoms react (11) with styrene, to form both polystyrene and an intractable material in which chromium is bonded to polystyrene. It would be interesting to ascertain whether such a polymeric material might have any catal3dic activity, in view of the current interest in polymer-sup-ported catalysts (51). 

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