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Solid-phase Synthesis of [4.4] Spirocyclic Oximes
Published on: February 6, 2019
Distinctive coordination behavior of a pyrazole imine-oxime compound towards Co(II) and Ni(II)
Samik Gupta1,2, M Fátima C Guedes da Silva1, Armando J L Pombeiro1
1Centro de Química Estrutural, Complexo I, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001, Lisboa, Portugal.
Abstract:
The polytopic Schiff base 5-methyl-1H-pyrazole-3-carboxylic acid 2-(hydroxyimino-1-methyl-propylidene)-hydrazide (H2L)was synthesized by the condensation of 5-methyl pyrazole-3-carbohydrazide and 3-(hydroxyimino)butan-2-one and its coordination ability was tested against cobalt (II) and nickel (II) nitrates. The ligand exhibited two different binding modes to form a unique binuclear triply bridged Co(III) cationic complex [Co2(1κN 2:2κN 2-L) (1κN 3:2κO 1-HL)2](NO3)2 (1). With the Ni(II) precursor, H2L was hydrolyzed to N',N˝-butane-2,3-diylidenebis (5-methyl-1H-pyrazole-3-carbohydrazide) (H2L1) which bound the metal cation in a tetradentate N3O1 fashion leading to the neutral square planar complex [Ni(κN 3 O 1-L1)]·MeOH (2·MeOH). Complexes 1 and 2 were characterized by IR, NMR, UV-Vis and single crystal X-ray crystallography. The probable mechanism for the Ni(II) mediated transformation of H2L into H2L1 has been investigated by ESI-MS.
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