Self-Assembly of Thiacalix[4]arene-Supported Nickel(II)/Cobalt(II) Complexes Sustained by in Situ Generated 5-Methyltetrazolate Ligand

Abstract

Solvothermal reactions of thiacalix[4]arene, NaN 3 , and acetonitrile in the presence of nickel(II)/cobalt(II) salts yielded four discrete complexes sustained by the in situ generated 5-methyltetrazolate ligand, [Ni II 12 (PTC4A) 3 (μ 6 -CO 3 ) 2 (μ-Mtta) 2 (μ-Mtta) 4 (μ 4 -Mtta) 2 (Py) 4 ]·7DMF·2Py·dma (1), [Co II 12 (PTC4A) arene; H 4 BTC4A = p-tert-butylthiacalix[4]arene; HMtta = 5-methyl tetrazolate). Crystal structural analyses revealed that complexes 1−3 are stacked by pseudotrigonal planar entities, which consist of three metal II 4 -thiacalix[4]arene subunits including two shuttlecock-like and one cylinder-like ones. These subunits are connected in an up-to-down-to-up fashion through six different 5-methyl tetrazolate anions. Both the in situ generated 5-methyl tetrazolate anion and carbonato anion play an important role in constructing these high-nuclearity clusters. When the corresponding chloride salt was used as precursors in the synthesis, complex 4 was obtained, which is stacked by wheel-like entities possessing four shuttlecock-like building blocks linked by eight in situ generated 5-methyl tetrazolate ligands in an up-to-up fashion. The differences in the structures of complexes 3 and 4 indicate that the geometry and size of the corresponding anions together with their coordinating properties are essential in determining the final structures. The magnetic properties of complexes 1−4 were examined, indicating strong antiferromagnetic interactions between the nickel(II)/cobalt(II) ions in the temperature range of 50−300 K. ■ INTRODUCTIONIn the past few decades, the design and synthesis of novel coordination architectures with in situ generated ligands under hydro(solvo)thermal conditions is a field of great interest in coordination and organic chemistry for the discovery of fascinating organic reactions and novel coordination complexes. 1 A large number of coordination complexes with an intriguing variety of architectures, topologies, and novel properties have been well prepared by in situ metal−ligand reactions under hydro(solvo)thermal conditions. Among the in situ reactions, tetrazoles are prepared through [2 + 3] cycloaddition reaction of nitriles and azide with the aid of a Lewis acid such as a zinc salt reported in 2001. 2 Since then, tetrazole-based ligands have been demonstrated to be excellent and versatile building blocks, with charge and multiconnectivity ability, to produce multidimensional coordination polymers with interesting optical, ferroelectric, magnetic, and hydrogen storage properties and potential energetic applications. 3 Up to now, the synthetic approach has been extended by varying transition metal ions and especially d 8 /d 10 metal ions (such as Zn II , 3a,c,g,k Cd II , 3g,a,e3b,d,k,m Hg II , 3m Cu I , 3h,i and Ag I3g ) have been investigated extensively. However, other paramagnetic transition metal ions (such as Cu II , 3m,g Mn II , 3f,j,l Co II , 3l,m and Ni II3k,m ) have rarely been explored. In addition, a few examples based on presynthesized tetrazoles and paramagne...

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