Aqueous solutions of a number of metal complexes have been found to dissolve cellulose. Recently, a number of new metal complexes have been developed that completely dissolve cellulose by deprotonating and coordinative binding the hydroxyl groups in the C2 and C3 position of the anhydro glucose. A detailed comparative light scattering study is given for cellulose in Schweizer's reagent (cuoxam), Ni-tren, and Cd-tren. Cuoxam is the well-known solution of cupric hydroxide in aqueous ammonia, and the abbreviation tren stands for tris(2-aminoethyl)amine. Cuoxam and Ni-tren are deep blue solvents. The light scattering measurements were carried out with the blue line of an argon ion laser at wavelength λ 0) 457.9 nm, and the data from these solvents required an absorption correction according to the Lambert-Beer law. Cd-tren is almost colorless, and the data could be used without correction. Because of traces of colloid particles, possibly originating from the metal hydroxides, a special treatment for optical clarification became necessary. A large number of samples, cotton linters, various pulp celluloses, and bacterial celluloses, were studied. All three solvents exhibited good solution properties, but only Cd-tren was capable of dissolving also the highest degrees of polymerization of cotton linters and bacterial cellulose (DP w) 9700). The limits for the two other solvents were DPw < 6300 for Ni-tren and DPw < 5300 for cuoxam. A fairly high chain stiffness was found with Kuhn segment lengths of lK) 15.8 (1.4 nm for Cd-tren, lK) 10.2 (0.8 nm for Ni-tren, and lK) 13.1 (1.2 nm for cuoxam, corresponding to characteristic ratios of C∝) 24.6, 15.4, and 19.4, respectively. The problem of preferential adsorption is discussed.

The mode of co-ordination of the multidentate ligand 2,2Ј-dimethyl-4,4Ј-bipyrimidine (L) was found to depend on the metal ion, the crystallization conditions, the metal-to-ligand ratio, and the anion. With nickel a chelating co-ordination through the endo-dentate nitrogen donor set is observed in the molecular complex [NiCl 2 (L)(H 2 O)]ؒCH 3 NO 2 , derived from hot CH 3 NO 2 . With Cu(NO 3 ) 2 and CuI-CH 3 CN one-and two-dimensional (1-D and 2-D) co-ordination polymers of formula ∞

A new synthetic route for the synthesis of 5,5Ј-diamino-2,2-NMR including 113 Cd-NMR, IR, and for the iron complex 57 Fe-Mößbauer spectroscopy. The structure of eight of the bipyridine (5) based on the coupling of 2-chloro-5aminopyridine in the presence of NiCl 2 × 6 H 2 O/PPh 3 /Zn in compounds was elucidated by X-ray crystallography. All of these metal complexes show a bipyridine-metal dimethylformamide is described. The reactions of the potentially ambidentate ligand 5 with salts of the transition coordination. The amino functionality was never involved in metal coordination. The intermolecular arrangement is metals Mn, Fe, Ni, Cu, Zn, Ag, and Cd gave a variety of 13 metal-ligand complexes depending on the anion, the dictated by hydrogen bonding from the amino functionality and by π-π stacking of the bipyridine rings. crystallization conditions and the metal-to-ligand ratio. The complexes obtained were characterized by thermal analyses,

Although the “brown‐ring” ion, [Fe(H2O)5(NO)]2+ (1), has been a research target for more than a century, this poorly stable species had never been isolated. We now report on the synthesis of crystals of a salt of 1 which allowed us to tackle the unique bonding situation on an experimental basis. As a result of the bonding analysis, two stretched, spin‐polarised π‐interactions provide the Fe–NO binding—and challenge the concept of “oxidation state”.

Nitrosyl–metal bonding relies on the two interactions between the pair of N–O‐π* and two of the metal's d orbitals. These (back)bonds are largely covalent, which makes their allocation in the course of an oxidation‐state determination ambiguous. However, apart from M‐N‐O‐angle or net‐charge considerations, IUPAC′s “ionic approximation” is a useful tool to reliably classify nitrosyl metal complexes in an orbital‐centered approach.