Realization of Unusual Ligand Binding Motifs in Metalated Container Molecules: Synthesis, Structures, and Magnetic Properties of the Complexes[(LMe)Ni2(μ-L′)]n+ with L′=NO3−, NO2−, N3−, N2H4, Pyridazine, Phthalazine, Pyrazolate, and Benzoate

Autor: Yves Journaux, Marco H. Klingele, Jean Jacques Girerd, Vasile Lozan, Berthold Kersting, Gunther Steinfeld, Julia Hausmann, Dieter Siebert
Rok vydání: 2004
Předmět:
Zdroj: Chemistry - A European Journal. 10:1716-1728
ISSN: 1521-3765
0947-6539
DOI: 10.1002/chem.200305705
Popis: A series of dinickel(II) complexes with the 24-membered macrocyclic hexaazadithiophenol ligand H 2 L M e was prepared and examined. The doubly deprotonated form (L M e ) 2 - forms complexes of the type [(L M e )Ni I I 2(μ-L')] n + with a bioctahedral N 3 Ni I I (m-SR) 2 (μ-L')Ni I I N 3 core and an overall calixarene-like structure. The bridging coordination site L' is accessible for a wide range of exogenous coligands. In this study L'=NO 3 -, NO 2 -, N 3 -, N 2 H 4 , pyrazolate (pz), pyridazine (pydz), phthalazine (phtz), and benzoate (OBz). Crystallographic studies reveal that each substrate binds in a distinct fashion to the [(L M e )Ni 2 ] 2 + portion: NO 2 -, N 2 H 4 , pz, pydz, and phtz form μ 1 , 2 -bridges, whereas NO 3 -, N 3 -, and OBz - are μ 1 , 3 -bridging. These distinctive binding motifs and the fact that some of the coligands adopt unusual conformations is discussed in terms of complementary host-guest interactions and the size and form of the binding pocket of the [(L M e )Ni 2 ] 2 + fragment. UV/Vis and electrochemical studies reveal that the solid-state structures are retained in the solution state. The relative stabilities of the complexes indicate that the [(L M e )Ni 2 ] 2 + fragment binds anionic coligands preferentially over neutral ones and strong-field ligands over weak-field ligands. Secondary van der Waals interactions also contribute to the stability of the complexes. Intramolecular ferromagnetic exchange interactions are present in the nitrito-, pyridazine-, and the benzoato-bridged complexes where J=+6.7, +3.5, and +5.8 cm - 1 (H= -2JS 1 S 2 , S 1 =S 2 =1) as indicated by magnetic susceptibility data taken from 300 to 2 K. In contrast, the azido bridge in [(L M e )Ni 2 (μ 1 , 3 -N 3 )] + results in an antiferromagnetic exchange interaction J=-46.7 cm - 1 . An explanation for this difference is qualitatively discussed in terms of bonding differences.
Databáze: OpenAIRE