ansa-Niobocene Complexes: Synthesis and Characterization of Novel Complexes [Me2Si(η5-C5H4)2]NbCl2and [Me2Si(η5-C5H4)2]NbCl(RC⋮CR) (R = Me, Ph). X-ray Crystal Structure of [Me2Si(η5-C5H4)2]NbCl(MeC⋮CMe)

The ansa-niobocene(IV) dichloride complex [Me 2 Si(η 5 -C 5 H 4 ) 2 ]NbCl 2 ( 1 ) has been prepared by the reaction of NbCl 4 (THF) 2 and [Me 2 Si(C 5 H 4 ) 2 ]Tl 2 in THF. The reduction of 1 by sodium amalgam in the presence of an alkyne (2-butyne or diphenylacetylene) yielded the ansa-niobocene(III) monochloride alkyne complexes [Me 2 Si(η 5 -C 5 H 4 ) 2 ]NbCl(RC⋮CR) (R = Me ( 2 ), Ph ( 3 )). Compounds 1 − 3 were characterized by IR, ESR, and NMR spectroscopy. In addition, the structure of 2 was determined by single-crystal X-ray diffraction.