Synthesis and characterisation of cis-dioxomolybdenum(vi) complexes of N-substituted 3-hydroxy-2-pyridinones

Abstract

The butoxy- and methoxy-derivatives (HL^c, and HL^b, respectively) of 1-[(ethoxycarbonyl)methyl]-3-hydroxy-2-(1H)-pyridinone, HL^a, were synthesized by transesterification and the mononuclear complexes [MoO₂(L^a–c)₂] were obtained by the reaction of the ligands with molybdenyl acetylacetonate. The three complexes were fully characterized by ¹H and ¹³C NMR spectroscopy, mass spectrometry and elemental analyses. A variable temperature NMR study showed that the N-substituents do not have a significant influence on the racemisation process of the complexes. The comparison of the crystal structure of [MoO₂(L^b)₂] with [MoO₂(L^a)₂] confirmed that an additional methylene group does not affect the immediate coordination environment of the molybdenum centre. The methoxy-derivative HL^b was also found to produce a dinuclear complex of composition [{MoO₂(L^b)O}₂], the structure of which was determined by X-ray diffraction.