Syntheses and Characterization by NMR Spectroscopy and X-ray Diffraction of Complexes Derived from Metals of Groups 2 and 13 and the Ligand Bis(3,5-di-tert-butyl-1-hydroxy-2-phenyl)amine

Abstract

Reaction of 3,5‐di‐tert‐butylcatechol and aqueous ammonia with boron, aluminum, gallium, or strontium chloride, or with calcium or barium acetate produce, under oxidizing conditions, neutral complexes of stoichiometric formulae ML (M = BCl), ML2, [M = Al (2), Ga (3), Ca (4), and Ba (5)], and ML3H [M = Sr (6)] [L = different oxidation states of bis(3,5‐di‐tert‐butyl‐1‐hydroxy‐2‐phenyl)amine]. The structures of 1 and 4–6 were established by 1H‐ and 13C‐NMR spectroscopy and of 2, 3, and 6 by X‐ray diffraction. The coordination compound ClBL (1) was obtained by transmetallation of ZnL2 with BCl3. It is a tetracyclic compound with tetracoordinated boron and nitrogen atoms, the ligand being in the reduced form, bis(hydroxyphenyl)amine. The paramagnetic complexes 2 and 3 crystallized in the triclinic system and are hexacoordinated with two orthogonal planar ligands bonded to the metal atoms. The ligands appear in two different oxidation states: one as the monoanion and another as a radical dianion. Based on their X‐ray diffraction molecular structures, it is deduced that both ligands have similar structures, confirming electronic delocalization and fast interconversion of their oxidation states. Ca and Ba complexes are diamagnetic and hexacoordinated, both ligands being monoanions The strontium complex crystallized in the monoclinic system, the metal atom is nonacoordinated, having two ligands as monoanions, and a third one is a neutral protonated diquinone. Its structure is a distorted helix with three paddles in a C3 geometry and its unexpected diamagnetic behaviour is due to the presence of a reduced protonated ligand.

Influence of Ligand Rigidity and Ring Substitution on the Structural and Electronic Behavior of Trivalent Iron and Gallium Complexes with Asymmetric Tridentate Ligands

“…Interestingly, this ion shows shorter distances than 2 . Structural data on gallium(III) ions coordinated to phenolate rings is limited, but the values above relate well with available information 27h…”

Coordination Effects on Electron Distributions for Rhodium Complexes of the Redox-Active Bis(3,5-di-tert-butyl-2-phenolate)amide Ligand

“…15,20,22 Spectral features in the near-IR portion of the UV−vis spectrum (λ max > 900) are often observed in metal complexes containing the semiquinonate form of the ligand, [ONO sq ] 2− , but were not observed in the spectra of 1 or 2a−d. 16,21,22 The broad visible transitions in 2a−d are similar to the metal-to-ligand charge-transfer (MLCT) transitions observed in rhodium complexes containing π-acceptor ligands such as bipyridine, phenanthroline, and other α-diimines, 42,66,75,76 in which the charge transfer character stems from interactions between filled metal d orbitals and antibonding ligand π* orbitals. Phosphine Binding Studies.…”

“…In comparison, the UV transitions in 2a – d are blue-shifted by 60 nm compared to the UV transition in 1 , and a broad, intense, visible-region absorption band dominates the spectra between 530 and 630 nm. These visible absorption bands are responsible for the blue-green colors of 2a – d , and are blue-shifted significantly from the ligand-based π→π* transition of [ONO q ]K discussed above. ,, Spectral features in the near-IR portion of the UV–vis spectrum (λ max > 900) are often observed in metal complexes containing the semiquinonate form of the ligand, [ONO sq ] 2– , but were not observed in the spectra of 1 or 2a – d . ,, The broad visible transitions in 2a – d are similar to the metal-to-ligand charge-transfer (MLCT) transitions observed in rhodium complexes containing π-acceptor ligands such as bipyridine, phenanthroline, and other α-diimines, ,,, in which the charge transfer character stems from interactions between filled metal d orbitals and antibonding ligand π* orbitals.…”

Optically active pentacyclic binuclear diorganotin compounds

“…We have been involved in the spectroscopic study of planar tetracyclic aromatic heterocycles derived from bis-phenolamines [1,2] their importance is based in their rigid structures which give stable compounds, suitable models for NMR and X-ray diffraction studies of hypervalent metallic atoms. The results motivated us to explore the reactions of diphenol-oxalamides with organometallic tin halides which afforded binuclear compounds with delocalized hexacyclic frameworks, being the tin atoms strongly coordinated to the amides oxygen atoms, Scheme 1 [3,4].…”