Rhenium(V) Oxo Complexes with Acetylacetone Derived Schiff Bases:  Structure and Catalytic Epoxidation

Abstract

Substitution reactions of rhenium(V) oxo precursors [ReOCl3(PPh3)2] or [NBu4][ReOCl4] with the bidentate acetylacetone-derived ketoamine ligands APOH = 4-anilino-3-penten-2-one, DPOH = 4-[2,6-dimethylanilino]-3-penten-2-one, and MTPOH = 4-[2-(methylthio)anilino]-3-penten-2-one gave the complexes [ReO(APO)Cl2(PPh3)] (1), [ReO(DPO)Cl2(PPh3)] (2), and [NBu4][ReOLCl3] (3, L = APO; 4, L = DPO; 5, L = MTPO), respectively. All complexes exhibit only one ketoamino chelate, independent of the amount of ligand added to the rhenium precursors. The complexes were characterized by 1H and 13C NMR spectroscopy. X-ray crystal structures of the complexes 1, 2, 4, and 5, including that of MTPOH, were determined, revealing the trans position of the two oxygen atoms and the trans-Cl,Cl conformation in 1 and 2, in contrast to most other rhenium complexes of this type where the cis-Cl,Cl conformation is observed. Coordination of the potentially tridentate ligand MTPOH in 5 is bidentate with a dangling thioether substituent. Compound 2 shows catalytic activity in the oxidation of cis-cyclooctene with tert-butylhydroperoxide.

Oxidorhenium(V) Complexes with Tridentate and Tetradentate Phenol‐Based Ligands

“…Molecular views are shown in Figure 1, crystallographic data are presented in Table 2, and selected bond lengths and angles are given in Table 1 The trans coordination of the ligand oxygen atom towards the oxygen atom attached to the rhenium atom is well documented in the literature. [7,18,[40][41][42] For distorted octahedral Re V O complexes with oxygen-containing bidentate ligands, it is suggested that O-Re=O corresponds to a minimum of trans weakening caused by the Re=O multiple bond. In addition, the repulsion exerted by the Re=O atom causes a compression field that tends to increase the mean O=Re-L cis angle beyond 90°.…”

“…The equatorial plane of the complexes consists of the two halide atoms, the nitrogen atom, and the chalcogen atom (compounds 1, 2, 9) or an additional nitrogen atom (compound 11) from the ligand. All complexes gave bond lengths for Re=O [18,20,44] In complex 1, the chlorine atoms Cl(1) and Cl(2) are coordinated in cis position to each other with comparable bond lengths of Re (1) …”

Crystal structure of diisothiocyanato-{2-[2-(1-pyridin-2-yl-ethylidene-amino) ethylamino]ethanol}zinc(II), Zn(NCS)2(C11H17N3O)

“…Schiff bases can coordinate many metal ions to form mononuclear or multinuclear complexes because of strong coordination ability and versatile coordination mode of the -C=N-group [1][2][3]. However, only limited Schiff bases of ketone and their complexes have been reported up to now [4][5][6][7].…”

Crystal structure of bis[2-bromo-4-chloro-6-((2,4-dimethyl-phenylimino)methyl)phenol]copper(II), Cu(C15H12BrClNO)2

“…Schiff bases have been widely introduced to construct the metal organic framework owing to their various coordination modes [1,2]. The title mononuclear Cu(II) complex is composed of one copper(II) ion and two Schiff base ligands.…”