Sterically hindered nickel- tripyrrins [Ni(trpy)X] with different di-, tri- and tetradentate anions X have been prepared with the aim of finding coordination polymers formed by self-association. The syntheses were performed by simple ligand-exchange reactions and proceeded successfully with the pseudohalides CN(-), OCN(-), SCN(-), SeCN(-), N(CN)(2) (-) (dicyanoamido, dca) and C(CN)(3) (-) (tricyanomethanido, tcm), the cyanidometallates [Ag(CN)(2)](-) and [Ni(CN)(4)](2-) and the salicylate anion (sal(-)). X-ray crystallographic analyses revealed that the complexes with cyanido and isocyanato ligands, as well as the compound with a salicylato ligand, are prototypes for structurally distinct monomeric species in the solid state, whereas one-dimensional coordination polymers or supramolecular three-dimensional networks are formed from all other combinations. The polymeric compounds display a variety of individual pillar and network architectures with functionalised pores and clefts and with the Ni(trpy) fragments in different relative orientations. Hydrogen bonding and pi stacking were found to be additional structure-directing effects, which increased the structural complexity of the system. The Ni(trpy) subunit has thus been proven to be a versatile building block for the construction of supramolecular assemblies and metal organic frameworks (MOFs) from pentacoordinate Ni(II) ions.
The metalation reactions of the 2,2'-bidipyrrin 4 with different rhodium(I) precursors yield the complexes 5 and 6 and the unusual corrinoid 7, depending only on the type of the ancillary ligand employed.
The hitherto unavailable free-base tripyrrins HTrpy have been prepared by cyanide promoted demetallation of a nickel(ii) tripyrrin and by acid-induced condensation of a diformylpyrrole and an alkylpyrrole with a sterically shielded alpha-position.
Rare vanadyl corrphycene and vanadyl 10-oxocorrole complexes were obtained via an oxidative macrocyclization process by the treatment of 6,6'-di-p-tolyl-2,2'-bidipyrrin with VO(acac)2 in a hot dioxygen atmosphere. The geometric and electronic structures of the new porpyhrinoids were determined and showed the dependency of the spectral pattern from the aromaticity of the macrocyclic ligand.
Neutral transition metal complexes of different alpha,omega-dimethyltripyrrins TrpyMX with M = Cu(II) and Zn(II) have been prepared with a variety of anionic halogeno and pseudohalogeno ligands X, and have been studied with respect to coordination modes and structural distortion. Only four- and five-coordinate species have been observed throughout the series. All four-coordinate species display unstrained, but distorted tetrahedral or strained and distorted square-planar coordination environments for zinc(II) and copper(II) species, respectively, thus following the expectations from simple ligand field arguments. Five-coordinate species do not form easily and were observed either in donor solvents or in the solid as 1D coordination polymers with distorted trigonal-bipyramidal coordination and different topologies.
The reaction of the open-chain tetrapyrrolic ligand 2,2'-bidipyrrin with molecular dioxygen in the presence of a catalytic amount of manganese(II)-acetate was found to produce 10,10'-diformyl-2,2'-bidipyrrin with a remarkable selectivity. To identify the active oxidant in this transformation, 2,2'-bidipyrrin was treated with potassium superoxide, sodium peroxide and manganese(III) acetate, respectively, in dry DMF. While superoxide produces the dialdehyde in high yield, the treatment with peroxide or manganese(III) acetate leads to decomposition only. Nickel(II)-, palladium(II)- and copper(II)-2,2'-bidipyrrin were found to undergo macrocyclization reactions when treated with potassium superoxide in dry DMF at room temperature. While the respective 10-oxocorrolates are formed from the nickel(II)- and palladium(II)-2,2'-bidipyrrins, the copper(II) chelate reacts very slowly and yields copper(III) corrole in low yield. The results strongly point to superoxide as the active oxidant in a recently found new synthesis of corroles.
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