The reaction of oxidorhenium(v) with dipodal and tripodal aroylhydrazines: formation of dinuclear and trinuclear aroylhydrazone-bridged rhenium(v) complexes

Abstract

The chemistry of aroylhydrazines has been attracting attention mainly due to the residual functional group, –CONH–NH₂, which has important effects on hydrophilicity and has the potential to provide special interaction sites for targeting molecules. The reaction of a dipodal aroylhydrazine, typically isophthalohydrazide (isphz), with trans-[ReOX₃(PPh₃)₂] in acetone led to the isolation of ligand-bridged oxidorhenium(V) dinuclear complexes (μ-dphz)[ReOX₂(PPh₃)]₂, (X = Cl (1), Br (2). The novel dianion dipodal aroylhydrazone Schiff base N′¹,N′³-di(propan-2-ylidene)isophthalohydrazide (dphz²⁻) was formed by the condensation of acetone with isphz and coordinated to each of the [ReO]³⁺ units as a monoanionic N,O-donor chelate, bridging via the dphz²⁻ dianion. The reaction of a tripodal aroylhydrazine, typically benzene-1,3,5-tricarbohydrazide (bthz), with trans-[ReOBr₃(PPh₃)₂] in acetone led to the isolation of the ligand-bridged oxidorhenium(V) trinuclear complex (μ-tbhz)[ReOBr₂(PPh₃)]₃ (3). The novel trianion tripodal aroylhydrazone Schiff base N′¹,N′³,N′⁵-tri(propan-2-ylidene)benzene-1,3,5-tricarbohydrazide (tbhz³⁻) was also formed from the condensation of acetone with bthz and coordinated to each of the [ReO]³⁺ units as a monoanionic N,O-donor chelate, bridging via the tbhz³⁻ trianion. The crystal structures, infra-red (IR), ¹H-NMR, and ³¹P-NMR spectroscopy of the complexes are reported. In addition, the density functional theory (DFT) calculations and the chromatographic behavior of the synthesised complexes are studied.