Quinone Oxygen-Coordinated Palladium(II) Complexes with Anthraquinone Ligands BearingN-Heterocyclic Coordination Sites

Abstract

The coordination properties of anthraquinone ligands bearing N-heterocyclic coordination sites to divalent palladium, and structural characterization of the quinone oxygen-coordinated palladium(II) complexes are described. The intramolecular NH···O (quinone) hydrogen bond [N(1)···O(2), 2.617 Å ] was observed in the crystal structure of 1-chloro-8-[2-(2-pyridyl)ethylamino]-9,10-anthraquinone (1a). The anthraquinone moieties of 1a are oriented in a face-to-face manner to form π-stacks in the crystal, with an interplanar distance of ca. 3.5 Å between the neighboring anthraquinone moieties. Complexation of 1a with Pd(OAc) 2 afforded the palladium(II) complex 2a. The quinone oxygen, which is bent out of the anthraquinone plane, is coordinated to the palladium(II) center, which is substituted by the amino nitrogen in a position trans to the pyridyl nitrogen in the crystal structure 2a. 1-(2-Phenylethylamino)-8-[2-(2-pyridyl)ethylamino]-9,10-anthraquinone (1b) was also found to form the 1:1 quinone oxygen-coordinated palladium(II) complex 2b. The single-crystal X-ray structure determination of 2b shows the existence of two independent molecules in the asymmetric unit. These two molecules are present in a good mirror image

What Is the Structure of the Antitubercular Natural Product Eucapsitrione?

“…The Suzuki–Miyaura coupling of dimethyl iodophthalate 10f , which should quite closely mimic the stereoelectronic properties of the iodochrysazins, was accompanied by saponification to give the phthalic acid 11f , but again, no direct arylation product 12f was observed (entry 8). The importance of oxidative properties of the chrysazin anthraquinone moiety , of 3 were also considered; benzoquinone (BQ) promotes a variety of C–H activations, − and so was also tested as an additive in the reaction with 2-iodophenol (entry 9), but this only led to a reduction in yield of the expected Suzuki–Miyaura product 11d . Finally, addition of an equivalent of chrysazin ( 2 ) to the experiment with 2-iodophenol ( 10d ) had no significant effect on the outcome of that reaction.…”

Nickel Complexes with Functional Zwitterionic N,O-Benzoquinonemonoimine-Type Ligands: Syntheses, Structures, and Catalytic Oligomerization of Ethylene

“…34 Although N,O-type ligands have recently been applied in coordination chemistry to the synthesis of porphyrin dimers and oligomers connected by metal ions, 35,36 only a few examples of mono-or polynuclear metal complexes based on N,O ligands supported by a quinonoid core have been reported. [37][38][39] A series of 2,5-disubstituted amino-p-benzoquinone ligands of the N,O,N,O type 1 has been used recently by Zhang and co-workers for the preparation of Ni(II) complexes of type 2, which were active as single-component catalysts in ethylene polymerization. 40 We recently reported the synthesis and electronic structure of the zwitterionic benzoquinonemonoimine ligand 3 from 4,6diaminoresorcinol dihydrochloride.…”

Ruthenium complexes of quinone related N-aryl-1,2-diimines. Metal mediated synthesis, X-ray structure and chemical reactionElectronic supplementary information (ESI) available: partial energy level diagram and molecular orbitals of 1c. See http://www.rsc.org/suppdata/nj/b2/b203956g/

“…These complexes feature multiple step redox processes due to changes of oxidation state of both the metal and the ligand themselves. Such metal complexes, in principle, may serve 7 as catalysts in catalytic redox reactions where both the ligands and metals are used as electron reservoirs.…”