Cobalt(II) 4-nitrobenzoates having pyridine as ancillary ligands and their catalytic role in the TBHP oxidation of alcohols

摘要

By making use of the Co~(2+)/pyridine (py)/O_2N-4-C_6H_4CO_2~- (4-nbz) system it has been possible to isolate two new complexes with markedly different stabilities: a purple form [Co(4-nbz)_2(py)_2] (1) and a pink form [Co(4-nbz)_2(py)_2(H_2O)_2] (2). These compounds have been characterized by single crystal X-ray diffraction. Compound 1 may be described as approximately tetrahedral, while compound 2 has Co(II) in a nearly octahedral environment. Both π-π stacking and weak C-H···O interactions appear to contribute to the moderate stability of the tetrahedral complex in the solid state. 2 displays an interesting supramolecular layered structure which is stabilized further by interlayer C-H···O interactions. Facile interconversion between 1 and 2 is found to occur in solid as well as solution phases. Apart from the synthesis, structure and spectral properties of these compounds, catalytic activity of 1 in the tert-butyl hydroperoxide (TBHP) oxidation of alcohols is also discussed in this paper.