Octahedral Co(III) complexes of 2-(phenylimino)pyrrolyl ligands: Synthesis and structural characterisation |
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Authors: | Clara SB Gomes Pedro T Gomes M Teresa Duarte |
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Institution: | a Centro de Química Estrutural, Departamento de Engenharia Química e Biológica, Instituto Superior Técnico, Universidade Técnica de Lisboa, Torre Sul, Av. Rovisco Pais, 1049-001 Lisboa, Portugal b Instituto de Biotecnologia e Bioengenharia, Centro de Engenharia Biológica e Química, Instituto Superior Técnico, Universidade Técnica de Lisboa, Torre Sul, Av. Rovisco Pais, 1049-001 Lisboa, Portugal |
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Abstract: | The reactions of CoCl2 with three equivalents of 2-(phenylimino)pyrrolyl sodium salts, performed under a nitrogen atmosphere, lead to the formation of the Co(III) complexes Co(κ2N,N′-NC4H3C(H) N-C6H5)3] (2a), Co(κ2N,N′-NC4H3C(CH3) N-C6H5)3] (2b) and Co(κ2N,N′-NC16H9C(H) N-C6H5)3] (2c), accommodating three chelating iminopyrrolyl ligands. Complexes 2a-c were obtained in moderate yields, and their characterisation by 1H, 13C NMR and X-ray diffraction show they are diamagnetic and have an octahedral geometry about the cobalt centre, respectively. Uncharacterised products were obtained in the same reaction involving ligand precursors such as 2-(2,6-dimethylphenylimino)pyrrolyl sodium salts, which is attributed to a greater steric hindrance in the coordination of three of these bulkier ligands. The redox behaviour of complexes 2a-c shows an irreversible reduction wave with a peak potential in the range −3.2 to −3.7 V. Upon reduction, the complexes decompose giving rise, in the case of 2a, to a redox pattern compatible with the formation of Co(κ2N,N′-NC4H3C(H) N-C6H5)2]. |
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Keywords: | Iminopyrrolyl ligands Cobalt(III) Octahedral complexes Redox behaviour |
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