Dinucleating Hybrid Ligands Providing a “Soft” P∩N and an Adjacent N-Rich Coordination Pocket − Controlled Synthesis of Unsymmetric Homodinuclear and Heterodinuclear Complexes

Abstract

New unsymmetric dinucleating pyrazolate ligands with different chelating side arms in the 3‐ and 5‐positions of the heterocycle have been prepared. These ligands provide a “soft” P∩N site and either an adjacent “N3” (HLa) or “N2S2” (HLb) coordination pocket, and they have been employed to build homo‐ and heterobimetallic complexes featuring various types of asymmetry. Both La and Lb form the mixed‐spin dinickel(II) chloride systems 4 and 5, respectively, which in the former case dimerizes via Cl bridges to give a tetranuclear compound. In the heterobimetallic complex 6 the PdII is specifically housed within the P∩N compartment. All new complexes have been characterized by X‐ray crystallography, and conformational and electronic coupling between the two metal ions of the dinuclear scaffolds have been analyzed.

Modelling Binuclear Metallobiosites: Insights from Pyrazole‐Supported Biomimetic and Bioinspired Complexes

“…Designing new ligand scaffolds which incorporate peripheral functionality capable of participating in hydrogen bonding is one approach which may contribute to rectifying this discrepancy. It is also noteworthy that reports employing truly asymmetric pyrazole‐based ligands for biomimetic studies are exceptionally rare, despite the existence of such organic scaffolds 9,124,125. Utilization of asymmetric ligands could aid in more faithfully reproducing the characteristics of many metallobiosites, and may afford homo‐ and hetereobimetallic complexes with unusual properties 126–128…”

Coordination Versatility of Pyrazole‐Based Ligands towards High‐Nuclearity Transition‐Metal and Rare‐Earth Clusters

“…The coordination of this type of ligands (HL6g) with cobalt(II) ions affords tetranuclear complexes, in which antiferromagnetic interactions are operative. [186,187] As a result, a linear trinuclear copper(II) compound has been synthesized with the H 3 L6i ligand that contains both an oxime and an acid substituent groups. [184] Weak antiferromagnetic interactions between the manganese(III) ions are observed.…”

“…[184] Weak antiferromagnetic interactions between the manganese(III) ions are observed. [186] Polytopic hydrazone-based ligands (H 2 L6n and H 4 L6o) containing the pyrazole group have been used for the synthesis of three different tetranuclear copper(II) grids. The same ligands used in combination with silver(I) yielded tetranuclear and octanuclear compounds depending on the substituents of the carbene ligand.…”

“…The coordination ability of ligands containing two different substituent groups on the pyrazole ring has also been explored 186,187. As a result, a linear trinuclear copper(II) compound has been synthesized with the H 3 L6i ligand that contains both an oxime and an acid substituent groups.…”

“…Strong antiferromagnetic interactions between the copper(II) ions are operative in this compound 187. Another example is a tetranuclear nickel(II) compound with the HL6k ligand, in which the nickel(II) ions are in low‐spin electronic configuration 186. Polytopic hydrazone‐based ligands (H 2 L6n and H 4 L6o) containing the pyrazole group have been used for the synthesis of three different tetranuclear copper(II) grids 188,189.…”