Schiff base chemistry of the {ReO} 3+ core: structural characterization of the unusual ‘3+2’ complex [ReO(η 3-OC 6H 4–CHNC 6H 4-2-S)(η 2-OC 6H 4[formula omitted])

Abstract

The reaction of [ReOCl 3(PPh 3) 2] with salicylaldehyde-2-mercaptoanil ( 1) in methanol yields [ReO(OCH 3)(PPh 3)(η 3-OC 6H 4CHNC 6H 4S)] ( 3). Reaction of 3 with 2-(2-hydroxyphenyl)benzothiazole ( 2) produces [ReO(η 3-OC 6H 4CHNC 6H 4S)(η 2-OC 6H 4 CNC 6H 4S )] ( 4) in good yield. Compound 4 may also be prepared directly from the reaction of [ReOCl 3(PPh 3) 2] with excess 1, after prolonged reaction times in the presence of atmospheric oxygen. The structure of 3 exhibits a distorted octahedral Re(V) center coordinated to a terminal oxo-group, a methoxy ligand, a triphenylphosphine ligand, and the N, O and S donors of the tridentate Schiff base ligand. The octahedral geometry of 4 is defined by the terminal oxo-group, the N, O and S donors of the tridentate Schiff base ligand, and the N and O donors of the bidentate 2-(2-hydroxophenyl)benzothiazole ligand. Oxidation and cyclization of the Schiff base salicylaldehyde-2-mercaptoanil to produce 2-(2-hydroxyphenyl)benzothiazole is precedented and in this instance may be driven by the formation of the robust ‘3+2’ complex 4.