Formation of an asymmetrical ligand ( H 3 L cyclic ) via a metal-induced cyclization of symmetrical thiocarbohydrazone ( H 4 L ) in synthesizing an oxovanadium(IV) complex VO( HL cyclic )(EtOH) 2.

Deng, Yuheng; Yang, Yingying; Zhang, Yajie; Yan, Qiaozhi; Liu, Juan

A symmetrical tetraprotic pentadentate (ONS) ligand, 1,5-bis(2-hydroxybenzaldehyde)thiocarbohydrazone (H 4 L), undergoes metal-induced cyclization to form an asymmetrical triprotic tetradentate ligand (H 3 L cyclic) containing a thiadiazole ring when it reacts with [VO(acac)2] under an aerobic environment in ethanol. The final isolated product is an oxovanadium(IV) complex, VO(HL cyclic)(EtOH)2 (1), which contains derived from H 4 L. Complex 1 has been characterized by X-ray single-crystal structure analysis, 1H NMR, and EPR. EPR spectrum demonstrates that the oxidation state of vanadium is 4. In 1, O–H ··· N/O–H ··· S hydrogen bond between the free phenolic hydroxyl and N/S of the thiadiazole ring are both possible, probed by density functional theory computation, showing that the hydrogen-bond energy of O–H ··· N is lower than that of O–H ··· S by 8.3 kcal mol−1 and is preferred.

TRANSITION metal complexes; VANADIUM compounds; RING formation (Chemistry); LIGANDS (Chemistry); HYDRAZONES; THIADIAZOLES; ASYMMETRIC synthesis; CRYSTAL structure

Journal of Coordination Chemistry, 2012, Vol 65, Issue 8, p1409

0095-8972

Academic Journal

10.1080/00958972.2012.673717