Bridging ability of a novel polydentate ligand (H2L) comprising an oxime function. Structures of a mononuclear precursor [NiL] and a dinuclear CuII2 complex. Magnetic properties of mononuclear (NiII and CuII), dinuclear (CuII2, NiII2, NiIICuII and CuIICrIII) and trinuclear (CuII3, CuIIMnIICuII and CuIIZnIICuII) complexes ‡

Abstract

A novel non-symmetrical polydentate Schiff base ligand 3-({2-[(1-methyl-3-oxobut-1-enyl)amino]ethyl}imino)-butan-2-one oxime (H 2 L) comprising an oxime function among various donor sites yields neutral [Ni II L] and [Cu II L] complexes. The structural determination of [NiL] confirms the deprotonation of the oxime function. The deprotonated oxime oxygen atom can react with auxiliary complexes to give homo-and hetero-di-and tri-nuclear entities. The structural determination of a homodinuclear copper complex clearly shows the presence of the expected oxime bridge, along with an unexpected ketonic bridge between the two copper centres leading to a Cu[O,NO]Cu core. A moderate antiferromagnetic interaction is present in the di-and tri-nuclear copper complexes. A similar interaction is also observed in the heteronuclear complexes (Cu II Ni II and Cu II Mn II ) and, more surprisingly, in the heterodinuclear Cu II Cr III entity. A generalization of the Cu [O,NO]Cu structure leads to a justification of these magnetic properties.In search of new polydentate bridging ligands we have been interested in designing a ligand (H 2 L, Fig. 1) which comprises an oxime function among various donor sites.Indeed it has been known for more than twenty years that oximato groups (᎐ ᎐ N᎐O Ϫ ) can bridge metal ions through their imino nitrogen and deprotonated oxygen atoms. Very generally double oximato bridges or association of a single N᎐O bridge with a second bridging ligand are involved in the resulting bi-or poly-nuclear complexes. Many types of homo-and heteropolynuclear complexes 1-15 have been obtained and magnetic investigations have revealed a great variety of behaviours, strong antiferromagnetism, weak antiferromagnetism and even ferromagnetism. It may be noted that singlet-triplet energy gaps of the order of 1000 cm Ϫ1 have been reported for oximato bridged dinuclear copper() complexes in which the double oximato bridge adopts the cis conformation. 3,10,11The present paper reports on the preparation, characterization and magnetic study of mononuclear Cu II and Ni II , dinuclear complexes involving the Cu II Cu II , Cu II Ni II and Cu II Cr III pairs and trinuclear complexes Cu II Cu II Cu II , Cu II Zn II Cu II and Cu II Mn II Cu II deriving from H 2 L. The structures of a mononuclear [NiL] precursor and a homodinuclear Cu II 2 complex are also reported.

Synthesis, crystal structures, hydrogen bonding graph-sets and theoretical studies of nickel (+II) co-ordinations with pyridine-2,6-dicarboxamide oxime

“…All other refinement details are available in the CIF (CCDC: 1401464). (2) 8.2058 (12) 114.691 (19) 2323.6(6) The Valance bond sum (1.995 A°) [30][31][32] confirms that the nickel ion in our complex is as A°and 109.47° (17), respectively, confirming a tetrahedral configuration (Table 3 and 4), similar to other perchlorates studied at low temperature) [37][38][39].…”

“…Structure, stability and reactivity of molecules, biochemical models, analytical and organometallic chemistry and particularly syntheses of molecules with unusual electronic properties are the aspects that kindled the interest for the oxime-based ligands [13][14][15][16][17]. Due to the marked ability to form bridges with metal ions, oxime ligands may be used to obtain polynuclear compounds with molecular magnetism and supramolecular structure [18,19]. Also, oxime-containing ligands are strong donors, and therefore, they were found to efficiently stabilize high oxidation states of metal ions such as CuII and NiII [20,21].…”

Do Trinuclear Triplesalen Complexes Exhibit Cooperative Effects? Synthesis, Characterization, and Enantioselective Catalytic Sulfoxidation by Chiral Trinuclear FeIII Triplesalen Complexes

“…[73][74][75][76] After several optimization steps, we synthesized successfully two chiral half units, 2 RR and 2…”

Synthesis and Structural Characterization of a Monofunctionalized Phloroglucin-Derivative: A Precursor for Heterotrinuclear meta-Phenylene Bridged Complexes

“…We adapted a template-directed protocol developed by Costes et al for the preparation of a salen 'halfunit', namely [(SE)Cu II (ImH)](ClO 4 ) with HSE = N-(2-aminoethyl)salicylaldimine [17] for the synthesis of the analogous 'half-unit' 3 3+ of our triplesalen ligands (Scheme 1) [16]. Under this protocol, we reacted 1 with three equivalents of Cu(ClO 4 ) 2 · 6H 2 O, imidazole, and ethylenediamine in an EtOH/H 2 O mixture and obtained green crystals in a low but reproducible yield.…”