Tetranuclear Nickel(II) Complexes Composed of Pairs of Dinuclear LNi₂ Fragments Linked by Acetylenedicarboxylate, Terephthalate, and Isophthalate Dianions: Synthesis, Structures and Magnetic Properties

Abstract

The tetranuclear nickel(II) complexes [(LNiII2)2(acetylenedicarboxylate)][BPh4]2 (2[BPh4]2), [(LNiII2)2(terephthalate)][BPh4]2 (3[BPh4]2), and [(LNiII2)2(isophthalate)][BPh4]2(4[BPh4]2), where L2– represents a macrocyclic hexaaza‐dithiophenolate ligand, have been synthesized and characterised by UV/Vis spectroscopy, IR spectroscopy, X‐ray crystallography, and magnetic susceptibility measurements. Each dicarboxylate dianion acts as a quadridentate bridging ligand linking two bioctahedral LNi2 units via μ1,3‐bridging carboxylate functions to generate discrete [(LNiII2)2(dicarboxylate)]2+ dications with a central LNi2(O2C–R–CO2)Ni2L core. The structures differ mainly in the distance between the center of the Ni···Ni axes of the isostructural LNi2 units (8.841(1) Å in 2[BPh4]2, 10.712(1) in 3[BPh4]2, and 9.561(1) in 4[BPh4]2) and the tilting angle between the two Ni2O2 planes (86.3° in 2[BPh4]2, 58.2° in 3[BPh4]2, 20.9° in 4[BPh4]2). Magnetic susceptibility measurements on the complexes over the range 2.0–295 K reveal the presence of weak ferromagnetic exchange interactions between the NiII ions within the dinuclear subunits with values for the magnetic exchange constant J1 of 23.1(5), 18.1(5), and 14.2(5) cm–1 for 2[BPh4]2, 3[BPh4]2, and 4[BPh4]2, respectively (H = –2JS1S2). The magnitude of the exchange interaction J2 across the dicarboxylate bridges is in all cases less than 0.1 cm–1, suggesting that no significant interdimer exchange coupling occurs in 2[BPh4]2–4[BPh4]2. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

The Synthesis of Tetrazoles in Nanometer Aqueous Micelles at Room Temperature

“…As can be seen, two [Ni 2 L] + units are united by the [Pd(csalen)] complex. The [Ni 2 L(O 2 C R )] + subunits are isostructural with other carboxylate complexes supported by the N 6 S 2 macrocycle 1,2. The carboxylate groups are coordinated in a bidentate bridging mode.…”

“…In the past ten years we have reported the synthesis of a number of tetranuclear, mixed ligand complexes of the type [{ M 2 L} 2 {μ‐O 2 C– R –O 2 C}] 2+ , in which { M 2 L} represents a bowl‐shaped complex unit supported by a macrocyclic N 6 S 2 donor ligand that embraces a bridging O 2 C– R –O 2 C 2– dicarboxylate dianion (Figure 1). Typical examples are Ni 4 complexes with acetylenedicarboxylato, terephthalato, isophthalato1 and 1, 1′‐ferrocene dicarboxylato2 ligands. They are readily prepared by substitution reactions between the chlorido‐bridged complex [Ni 2 L(μ‐Cl)] + and the corresponding dicarboxylato dianion 3.…”

Steric Effect of a Capping Ligand on the Formation of Supramolecular Coordination Networks of Ni(II): Solid-State Entrapment of Cyclic Water Dimer

“…These parameters are in the range of those found in mono- and bis(adc) bridged dinuclear and polynuclear compounds. 28 , 29 , 35 , 37 , 38 The selected bond distances and angles are listed in Tables S1 and S2 . A 14-membered ring with dimensions 7.952 Å × 3.277 Å ( Figure 2 ) is formed by two Ni(II) centers, four oxygen atoms, and eight carbon atoms (from both adc).…”

Selective complexation of α-amino acids and simple peptides via their carboxylate groups

“…, in which pairs of bioctahedral [LNi 2 ] 2+ units are joined by a dicarboxylato dianion. 33 In some of these complexes, the carboxylate ions adopt unusual conformations attributable to confinement as for instance in [LNi 2 (μ-3,4dimethyl-6-phenylcyclohex-3-enecarboxylate)], where the phenyl ring and the carboxylate group both assume axial positions with respect to the cyclohexene ring. 34,35 The high carboxylate ion affinity of the [LNi 2 ] 2+ fragment suggested that a selective coordination of amino acids and simple peptides is possible.…”