Heteroleptic Complexes of the Tridentate Pyridine‐2, 6‐di‐tetrazolate Ligand. Issue 21 (25th July 2017) - Krest, Alexander
Abstract: The synthesis and spectroscopic characterisation of a series of heteroleptic complexes of the tridentate pyridine‐2, 6‐di‐(5‐tetrazolate) (pydtz 2− ) with Co(II), Ni(II), Cu(II) and Zn(II) and pyridine (Py) and H2 O as coligands is reported. Single crystal XRD data reveals the formation of octahedrally configured complexes [Co(pydtz)(H2 O)(Py)2 ], [Co(pydtz)(H2 O)2 (Py)]⋅2H2 O, [Ni(pydtz)(Py)3 ]⋅2Py, and [Zn(pydtz)(H2 O)(Py)2 ]⋅Py, and a markedly Jahn‐Teller distorted octahedral structure for [Cu(pydtz)(H2 O)2 (Py)]. Magnetic measurements reveal a S = 3/2 high‐spin configuration for the Co(II) complex [Co(pydtz)(H2 O)(Py)2 ], an S = 1 ground state for the Ni(II) derivative and S = 1/2 Cu(II) ions for [Cu(pydtz)(H2 O)2 (Py)], the latter is supported by electron‐paramagnetic‐resonance spectroscopy. The crystalline materials are subject to severe corrosion as revealed by powder XRD and DSC‐TG experiments. H2 O and pyridine co‐crystallisates and coligands are easily cleaved. At the same time DSC‐TG reveal very high stability of the [M(pydtz)] fragments with exothermic decomposition at T > 300 °C. As a consequence, in pyridine solution in all cases the species [M(pydtz)(Py)3 ] are observed. Ultraviolet‐visible light absorption spectroscopy reveals a strong ligand field procured by the pydtz 2− ligand and electrochemical measurements suggest very strong σ‐donation but only weak π‐accepting abilities of pydtz 2− compared to the isostructural terpy (2, 2';6', 2''‐terpyridine) ligand. Abstract : The new compounds [Co(pydtz)(H2 O)(Py)2 ], [Co(pydtz)(H2 O)2 (Py)]⋅2H2 O, [Ni(pydtz)(Py)3 ]⋅2Py, [Cu(pydtz)(H2 O)2 (Py)] and [Zn(pydtz)(H2 O)(Py)2 ]⋅Py containing the tridentate ligand pyridine‐2, 6‐di‐(5‐tetrazolate) (pydtz 2− ) ligand have been characterised by single‐crystal XRD, EPR spectroscopy, magnetic measurements, UV‐vis absorption spectroscopy and electrochemical investigations to asset the specific metal‐ligand interactions of this ligand. The [M(pydtz)] fragment turns out to be quite stable and the pydtz 2− ligand provides a strong ligand field.