Oxovanadium(IV) and dioxomolybdenum(VI) complexes: synthesis from the corresponding acetylacetonato complexes and X-ray structures

Abstract

Displacement of acetylacetonate (acac) from oxometal complexes of this ligand in the reaction with the acidic form of 7,16-dihydro-6,8,15,17-tetramethyldibenzo[b,I][1,4,8,11] tetra-azacyclotetra-decine (H₂L) is a stepwise process. The reaction of [MoO₂(acac)₂] with H₂L in tetrahydronaphthalene gave a partial displacement of the acetylacetonato ligand and formation of [MoO₂(acac)(HL)](1). Two nitrogen atoms only from the macrocycle bind molybdenum, which is six-co-ordinate with the two oxo groups in a cis arrangement [ν(Mo–O)895 and 927 cm^–1]. A complete displacement of the acetylacetone occurs in [VO(acac)₂] leading to the formation of [VO(L)](2). Vanadium has a pseudo-square-pyramidal co-ordination geometry in (2), with the L ligand assuming the usual ‘saddle’ shape conformation [ν(V–O) 978 cm^–1]. The structures of (1) and (2) have been determined by X-ray analysis.