Microwave synthesis of mono- and bis-tetrazolato complexes via 1,3-dipolar cycloaddition of organonitriles with nickel(II)-bound azides: Isolation of 5-substituted tetrazoles from parent complex

[2 + 3] Cycloaddition reaction of diazidonickel(II) complexes cis-[Ni(N-3)(2)(phen)(2)] I with organonitriles NCR 2 under microwave irradiation give the bis(tetrazolato) complexes cis-[Ni(N4CR)(2)(pben)(2)] [R = Ph (3a), 4-NC5H4 (3b), 3-NC5H4 (3c), 4-CNPh (3d)]. Treatment of the tetrazolato complexes with excess of NaN3 liberates the free tetrazoles from the parent metal complexes. Reaction of 2-cyanopyridine with cis-[Ni(N-3)(2)(phen)(2)] 1 in presence of NaClO4 gives a mono(tetrazolato) complex [Ni(5-(2-pyridyl)-tetrazolato)(phen)(2)](ClO4) 3e along with formation of pure 2-(1H-tetrazol-5-yl)-pyridine. Reaction of tetracyanoethylene with cis-[Ni(N-3)(2)(biPy)(2)](4) at room temperature produced a bis(tetrazolato) complex [Ni{2-cyano-3-(tetrazolato-5-y1)-but-2-enedintrile}(2)(biPy)(2)] 5. A monoazidonickel complex [Ni(N-3)(H2O)-(Pben)(2)]ClO4 6 was isolated as a minor product during the synthesis of cis-[Ni(N-3)(2)(phen)(2)] I. All the complexes obtained were characterized by IR, elemental analyses and ESI-MS apart from single crystal X-ray crystallography. (C) 2013 Elsevier Ltd. All rights reserved.