5‐Cyanotetrazolate as a Ligand and Linker in Copper(II) Complexes and Coordination Polymers

Abstract

5-Cyanotetrazole readily forms from (CN)2 and HN3. The coordination abilities of the 5-cyanotetrazolate anion N4CCN– (ctz) towards CuII ions were examined and a series of complexes and coordination polymers were synthesized and characterized by single-crystal structure analyses: PPh4[Cu(ctz)3] (1), [Cu(ctz)2(bipy)] (2, bipy = 2,2′-bipyridine), [CuCl(py)4](ctz)·2py (3, py = pyridine), [Cu2(ctz)6Cu(CH3CN)2(H2O)2]·2CH3CN (4a), [Cu2(ctz)6Cu(H2O)3{(CH3)2CO}]·3(CH3)2CO (4b), [Cu(ctz)2(py)4] (5), [Cu2(ctz)4(bipy)2] (6) and [Cu2(ctz)2(tpm)2(NO3)]NO3 [7, tpm = tris(pyrazol-1-yl)methane]. As ctz is a multidentate linker, additional neutral coligands such as monodentate py, bidentate bipy and tridentate tpm ligands were used to avoid the formation of noncrystalline polymers. The structures of 1–7 reflect the versatile coordination abilities of ctz in the various types of coordination environments of the CuII ions and dimensionalities of the linkages. The structures represent 1D chain motifs (1, 2 and 3), 2D layered structures (4a and 4b), mononuclear (5) and dinuclear complexes (6 and 7). Magnetic coupling phenomena were detected by susceptibility measurements of 1, 4a, 6 and 7, which were fitted to the magnetic models according to antiferromagnetic spin-pairing of two S = 1/2 systems (Bleaney–Bowers) for 6 (J = –0.53 cm–1) and 7 (J = –2.91 cm–1), to the ferromagnetic high-temperature series expansion based on the Baker 1D (S = 1/2) chain model for 1 (J = +14.4 cm–1) and to the Néel model of ferrimagnetism for 4a. The diverse magnetic interactions between the Cu2+ sites are communicated by the bridging ctz anions.