COMPLEXES ISOLATED FROM SYSTEMS OF Ni(II) OR Co(II) WITH NCOAND PYRAZOLE TYPE LIGANDS. NOVEL EXAMPLES OF NUCLEOPHILIC ADDITION IN THE METAL COORDINATION SPHERE AND OF COLIGAND ISOMERISM

Abstract
From M(II) [sbnd] NCO - L systems [M(II) = Ni(II), Co(II); L = pyrazole (pz), 3,5-dimethylpyrazole (dmpz), 3,4,5-trimethylpyrazole (tmpz)] the following new solid compounds were prepared: Ni(NCO)2L4, Ni(NCO)2(tmpz)2, Ni(tmpz. NCO)2, Co(NCO)2(pz)4, and Co(NCO)2L2, where L = dmpz, tmpz. Spectroscopic and magnetic data were used for the purpose of assigning probable structures to the compounds. For Ni(NCO)2L4, where L = dmpz, tmpz, and Ni(NCO)2(tmpz)2 polymeric structures with N-bridging NCO groups are accepted, in the case of the 1:4 compounds with two L molecules out of the coordination sphere. Planar Ni(tmpz. NCO)2 contains 3,4,5-trimethyl-1-carbamoylpyrazolate anions as chelate ligands, formed by C(NCO) - N(imine) nucleophilic addition in the Ni(II) coordination sphere; this compound is a coligand isomer of Ni(NCO)2(tmpz)2. Also, the compound Co(NCO)2(pz)3 was isolated, in which equilibria between the Co(II)-pz. NCO and Co(II) [sbnd] NCO species were ascertained.

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