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 (mu-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 (dphz(2-)) 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 dphz(2-) 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 (mu-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 (tbhz(3-)) 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 tbhz(3-) trianion. The crystal structures, infra-red (IR), H-1-NMR, and P-31-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.