Intra‐ and Intermolecular H···Cl–Ni Bonding Patterns in a Series of Highly Preorganized Dinuclear Nickel(II) Complexes

Abstract

Four dinickel complexes [L1Ni2(μ‐Cl)(Cl)2]·2CH3OH (1a), [L1Ni2(μ‐Cl)(CH3OH)](ClO4)2 (1b), [L2Ni2(μ‐Cl)Cl2(H2O)2]·H2O (2) and [L3Ni2Cl2(CH3OH)2]Cl·2CH3OH (3) were synthesized and structurally characterized. The ligand scaffolds have a central pyrazolato bridge and N‐donor chelate arms that provide two proximate binding pockets for the nickel ions. While the longer ligand side arms in 1a, 1b and 2 induce Ni···Ni distances of around 4.0 Å and favour incorporation of a chlorido bridge within the dimetallic pocket, a stretched Ni···Ni separation of 4.6 Å with an unusual intramolecular Cl···H–O linkage is observed in 3. Various Cl···H–O hydrogen‐bonding motifs are identified in the solid‐state structures of 1–3, where either the H‐donor (MeOH or H2O) or the H‐acceptor (chlorido) or both are bound to a nickel ion, and their relative donor–acceptor distances are discussed. Magnetic coupling mediated through the pyrazolato and chlorido bridges is rather weak and antiferromagnetic, but it is even weaker for the Cl···H–O linkage. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Di- and Tetra-Nuclear Copper(II), Nickel(II), and Cobalt(II) Complexes of Four Bis-Tetradentate Triazole-Based Ligands: Synthesis, Structure, and Magnetic Properties

“…There are eight structurally characterized dinuclear octahedral nickel(II) complexes of bis-tetradentate pyrazolate -based ligands in the literature. − As expected, the Ni–N pyrazolate bonds are slightly shorter, due to the negatively charged nature of the pyrazolate ring, 1.943(4)–2.144(3) Å, than the Ni–N triazole bonds in the triazole complexes reported in this work, 2.040(3)–2.119(4) Å (Table ). The Ni–N amine and Ni–N py bonds in the pyrazolate complexes (2.096(3)–2.205(1) and 2.043(3)–2.178(5) Å, respectively) are similar or slightly longer than in our triazole complexes (2.093(3)–2.132(4) and 2.039(4)–2.082(3) Å, respectively, Table ).…”

Establishing the Family of Diruthenium Water Oxidation Catalysts Based on the Bis(bipyridyl)pyrazolate Ligand System

“…The chlorido-aqua coordination motif can thus be considered as a dynamic bridging unit. This process likely goes via dissociation of the water molecule and possibly via a chlorido bridged intermediate, followed by reinsertion of water. Exchange of H 2 O in related (H)­O···H–O­(H) bridging units was previously shown to proceed rapidly …”

Two dinuclear iron(ii) complexes K[Fe2(L1)(SCN)4]·2(C3H8O) and [Fe2(L1)(SeCN)3(C5H5N)]·H2O are stabilised in the ‘[HS–LS]’ state by a bis-tetradentate pyrazolate-based ligand

“…Meyer and co-workers have shown that ligand (L 1 )is capable of producing dinuclear systems in which the metal ions [copper(II), 10 zinc(II), 11 nickel(II) 12 ] are singly-bridged by the central pyrazolate moiety and coordinated to the tertiary amine and the two pyridine donors of the pendant arms, with the two last positions occupied by solvent or anion molecules. This is exactly the binding mode we wish to see adopted, but for iron(II), and preferably with the last two positions occupied by coordinating anions that are known to help confer SCO-activity on the iron centres, such as NCS and NCSe.…”