Tridentate coordination of dioxomolybdenum(VI) with some potentially quinquedentate (N₂O₃) Schiff base ligands

Three complexes of molybdenum(VI) 4-6 have been prepared and characterised using potentially quinquedentate ligands derived from Schiff base condensations using 1,3-diamino-2- hydroxypropane. From NMR spectroscopic evidence it is clear that the ligands bind to the metal ion in a terdentate manner, leaving two of the possible ligand donor atoms uncoordinated. This represents a new coordination mode for monomeric complexes of these ligands with a transition metal ion. In solution, the sixth coordination site of the MoO₂²⁺ ion is occupied by a solvent molecule while in the solid state, the ¹³C NMR spectrum of 4 suggests that the sixth coordination site of MoO₂²⁺ is occupied by a phenolic oxygen, probably via an intermolecular interaction between the complexes. © 1993.