Reactivity of nitrosodicyanomethanide towards Ni(II)

From the system Ni(II)-ONC(CN)(2)(-)-L, where L = pyrazole (pz), 3(5)-methylpyrazole, 3,5-dimethylpyrazole, 3,4,5-trimethylpyrazole (tmpz) and indazole in aqueous and aqueous-methanolic media, compounds of two types were isolated, Nitrosadicyanomethanide compounds of the type [Ni{ONC(CN)(2)}(2)L(4)], according to spectroscopic results, have octahedral structures with nitroso nitrogen bonded ONC(CN)(2)(-) anions. Compounds of the second type, [Ni{ONC(CN)(2) . CH3OH}(2)L(2)], where L = pz, H2O, tmpz, contain anionic chelate ligands NO(CN)CC(OCH3)NH- which arise by nucleophilic addition of methanol oxygen to the cyano carbon of ONC(CN)(2)(-) in the Ni(II) coordination sphere. This was established by X-ray crystallography of compounds with L = pz and H2O. The compound [Ni{ONC(CN)(2) . CH3OH}(2)(H2O)(2)] is triclinic, space group P (1) over bar, with a = 5.007(1), b = 6.576(3) and c = 10.721(3) Angstrom, alpha = 75.63(3), beta = 86.79(2) and gamma = 78.65(2)degrees, and Z = 1. Full-matrix least-squares refinement gave R = 0.0372 and Rw = 0.0973 for 1304 reflections. The Ni(II) environment is a slightly elongated rhombic bipyramid, the anionic ligands forming five-membered rings with water molecules in axial positions, The compounds with L = pz or tmpz (as hemihydrates) show the same anionic ligands, but pz or tmpz molecules are located in cis-position.