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][ReVOCl4] and on the six-coordinate rhenium precursor [ReVOCl3(PPh3)2]. The chlororhenium intermediate species [ReVOCl(Ph–SNO–CH3)] 1 allows the formation of the homologous iodo complex [ReVOI(Ph–SNO–CH3)] 2 by a halogen exchange reaction with lithium iodide. The similar complexes [ReVOCl(Ph–SNO–H)] 3 and [ReVOCl(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 [ReVOCl(Ph–SNO–H)(PPh3)] 5 and [ReVOCl(Naph–SNO–H)(PPh3)] 7 which are smoothly converted in ethanolic solution into [ReVOCl(Ph–SNO–H)(OPPh3)] 6 and [ReVOCl(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.