Synthesis, properties and spectroscopic studies of rhenium(v) complexes stabilized by tridentate Schiff bases derived from S-methyl dithiocarbazate

Abstract

Neutral oxorhenium(V) complexes with tridentate SNO Schiff bases have been prepared by substitution reactions on the square pyramidal ionic complex [NBu₄][Re^VOCl₄] and on the six-coordinate rhenium precursor [Re^VOCl₃(PPh₃)₂]. The chlororhenium intermediate species [Re^VOCl(Ph–SNO–CH₃)] 1 allows the formation of the homologous iodo complex [Re^VOI(Ph–SNO–CH₃)] 2 by a halogen exchange reaction with lithium iodide. The similar complexes [Re^VOCl(Ph–SNO–H)] 3 and [Re^VOCl(Naph–SNO–H)] 4 have been synthesised using S-methyl-β-N-(2-hydroxyphenylmethylidene)dithiocarbazate (Ph–SNO–H) and S-methyl-β-N-(2-hydroxynaphthylmethylidene)dithiocarbazate (Naph–SNO–H). The ionic complex [NBu₄][ReOCl₄] reacts with 4 equivalents of PPh₃ and Ph–SNO–H or Naph–SNO–H to give rise to the complexes [Re^VOCl(Ph–SNO–H)(PPh₃)] 5 and [Re^VOCl(Naph–SNO–H)(PPh₃)] 7 which are smoothly converted in ethanolic solution into [Re^VOCl(Ph–SNO–H)(OPPh₃)] 6 and [Re^VOCl(Naph–SNO–H)(OPPh₃)] 8, respectively. Each compound was characterised by elemental analysis, IR, NMR spectra and FAB mass spectrometry. The crystallographic structures of [ReOI(Ph–SNO–CH₃)] 2, [ReOCl(Ph–SNO–H)(PPh₃)] 5 and [ReOCl(Ph–SNO–H)(OPPh₃)] 6 were determined by single crystal X-ray diffraction methods.