Preparation and characterization of mononuclear Co, Ni, and Zn complexes of dinucleating macrocyclic hexaaza-dithiophenolate ligands and their open-chain derivatives

Abstract

The preparation and characterization of mononuclear complexes of the dinucleating 24-membered hexazadithiophenolate macrocycles H2L2 and H2L3 and their open-chain N3S2 analogues H2L4 and H2L5 are reported. The highly crystalline compounds [Ni(L4)] (4), [Ni(L5)] (5), [Co(L5)] (6), [NiH2(L2)]2+ (7), [ZnH2(L2)]2+ (8), and [NiH2(L3)]2+ (9) could be readily prepared by stoichiometric complexation reactions of the hydrochlorides of the free ligands with the corresponding metal(II) dichlorides and NEt3 in methanolic solution. All complexes were characterized by X-ray crystallography. Monometallic complexes 4-6 of the pentadentate ligands H2L4 and H2L5 feature distorted square pyramidal MN3S2 structures (tau = 0.01 to 0.44). Similar coordination geometries are observed for the macrocyclic complexes 7-9 of the octadentate ligands H2L2 and H2L3. The two hydrogen atoms in 7-9 are attached to the noncoordinating benzylic amine functions and are hydrogen bonded to the metal-bound thiophenolate functions. A comparison of the structures of 4-9 reveals that the macrocycles L2 and L3 have a rather flexible ligand backbone that do not confer unusual coordination geometries on the metal ions. We also report on the ability of the monometallic complexes 7 and 8 to serve as starting materials for the preparation of dinuclear complexes.

Chemistry of metalated container molecules

“…The NMR signals of the coligands are shifted downfield from their values in the uncomplexed form [47,51,56]. The shift to higher field can be explained by the ring current effect.…”

Preparation and Characterization of Mononuclear Ni Complexes of Tetradentate Amine-thioether and Amine-thiolate Ligands

“…In recent work, we described the synthesis of the pentadentate amine-thiophenol ligands H 2 L 4 and H 2 L 5 [13]. We now find that the N 2 S 2 ligands H 2 L 6 and H 2 L 7 can be prepared in a similar manner.…”

“…Complex [Ni II (L 6 )] (10) forms as the only isolable product, when H 2 L 6 · 2HCl is treated with NiCl 2 · 6H 2 O and NEt 3 in a 1 : 1 : 2 molar ratio in methanolic solution. Similarly, the reaction of H 2 L 7 · 2HCl with NiCl 2 · 6H 2 O and NEt 3 in methanol produced the red neutral complex [Ni II (L 7 )] (11 13 C NMR spectroscopy) and compounds 9 -13 also by X-ray crystallography. The infrared spectra of the complexes 9 -11 and 14 reveal mainly the various stretching and bending modes of the supporting ligands.…”

Hexaaza‐dithia Macrocycles Containing Pendant Methoxyethyl Groups: Synthesis and Characterization of Mono and Dinuclear Nickel Complexes

“…[22] In addition, the Ni atom sits ca 0.35 Å www.zaac.wiley-vch.de ARTICLE above the plane through the above atoms, being directed towards S1, which forms the apex of the pyramid, and the metal-ligand bond lengths resemble more those of five-coordinate Ni II complexes with N 3 S 2 coordination. [23][24][25] It should be noted in this respect that the conformation of the macrocycle in this compound is also virtually identical with that in [Ni(H 2 L1)] 2+ , [26] indicative of little -if any -stereochemical influence of the 2-methoxyethyl substituents. The structure is further stabilized by two intramolecular NH···S hydrogen bonding interactions (N4···S2 3.131 Å, N6···S1 3.230 Å).…”

“…[17] So far, is has not been applied to the deprotection of bicyclic aza-thioether. [18] indicating that both species exist as pentacoordinate species in solution state. Nevertheless, it is not possible to distinguish between a trigonal-pyramidal or a square-pyramidal coordination environment.…”