A Tetranuclear Hydroxo‐Bridged Copper(II) Complex with PrimaryN‐Acylamidines as Ligands: Preparation, Structural, and Magnetic Characterisation

Abstract

The reaction of N‐pivaloylbenzamidine (1a) and tetrakis(acetonitrile)copper(I) hexafluorophosphate in the presence of air yields a hydroxo‐bridged copper(II) complex (4). The product was characterised by X‐ray diffraction analysis and found to be a cubane‐like dimeric complex consisting of two square dimers with the formula [{(1a)2Cu2(OH)2}2](PF6)4·4 CH2Cl2 (4·4 CH2Cl2) with cupric ions and hydroxyl oxygen atoms at alternating vertices of a cube. The complex can be described as consisting of two [ligand‐Cu‐(OH)2‐Cu‐ligand] units held together by long out‐of‐plane Cu–O bonds, creating a tetrameric entity with a Cu4(OH)4 core. Each cupric ion is essentially square‐pyramidally coordinated, being bound to three OH bridges, one N atom of the amidine and one N‐acylamidine O atom. The magnetic properties of this compound have been studied in the 2–300 K temperature range. The measurements revealed that the cupric ions in the cube are antiferromagnetically coupled. This observation has been rationalised on the basis of the structural data. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Pyridine‐Based Oligonitriles as Pincer Ligands for Palladium(II), Copper(II), Cobalt(II), and Nickel(II) Ions

“…Other known examples are N-acylamidine complexes of Cu II , which show chelating monomeric 1:1, 2:1 and tetrameric 1:1 moieties. [3,4] In contrast, Pd II forms 2:1 complexes with N-acylamidines where the ligand acts in a monodentate fashion. Such compounds activity in Suzuki-Miyaura cross-coupling reactions.…”

“…[1] Recently, we were able to show that 1-oxa-3,5,7,9-tetraazadecapentaenes have the potential to act as chelating ligands with Pd II ions in metal coordination reactions. [2] Similarly, a peramino derivative [2,4,6,8,8-pentakis(dimethylamino)-1-oxa-3,5,7-triazaoctatetraene] forms a complex with ZnCl 2 by chelating through the oxygen atom O1 and the nitrogen atom N5. Other known examples are N-acylamidine complexes of Cu II , which show chelating monomeric 1:1, 2:1 and tetrameric 1:1 moieties.…”

Enantiomerically Pure Copper(II) Cubanes [Cu4L2(OMe)4] from Chiral Bis‐1,3‐diketones H2L through Diastereoselective Self‐Assembly

“…[9,10] For that reason, the synthesis of chiral, enantiomerically pure singlemolecule magnets is of special interest (e.g. for magnetodichroism [11] ), and complexes like cubane 7 and ent-7 are potential candidates.…”

“…Cubane 7 exists as a single enantiomer, crystallizes in the chiral monoclinic space group C2, and possesses a [Cu 4 (m 3 -O) 4 ] cubane core unit [9] consisting of two interpenetrating tetrahedra: one made up of four copper ions and one of four m 3 -OMe ligands. The metal-metal separations in 7 are 2.98 and 3.25 .…”

Compatibility of a Gaseous Dielectric with Al, Ag, and Cu and Gas‐Phase Synthesis of a New N‐Acylamidine Copper Complex

“…In the past 20 years N ‐acylamidines have been investigated mainly by the Würthwein group . The three heteroatoms (one oxygen and two nitrogen atoms) offer various coordination modes for transition metals.…”