Abstract
A series of new ring-functionalized niobocene dichloride compounds (RCH2C5H4)2NbCl2 (R = MeOCH2, (CH2)5NCH2, 2-MeOC6H4, 3-MeOC6H4, 4-MeOC6H4, 2,4-(MeO)2C6H3, 3,4-(MeO)2C6H3, 2,4,6-(MeO)3C6H2, 3,4,5-(MeO)3C6H2, 4-FC6H4, 4-Me2NC6H4) was synthesized and characterized by electron paramagnetic resonance. Three structures were determined by X-ray diffraction analysis and revealed the expected bent metallocene structure with two cyclopentadienyl ligands and two chlorides coordinated to niobium in the oxidation state IV.
Chlorides and the centroids of the η5-bonded cyclopentadienyl rings define a distorted tetrahedron. The cytotoxicity study has demonstrated that substitution with methoxybenzyl groups can lead to highly active species, but the activity strongly varies with the number and positions of the methoxy groups in the benzene ring.
The most active species under study - {2,4-(MeO)2C6H3CH2C5H4}2NbCl2 - has a maximal inhibitory concentration value comparable with cisplatin.