Synthesis and reactivity of [2]disilaniobocenophanes

The paramagnetic ansa-niobocene [(Me2Si)2(η5-C5H4)2NbCl2] (1) was obtained from the reaction of Li2[(Me2Si)2(C5H4)2] with [NbCl4(thf)2]. Further treatment with Li[AlH4] yielded [(Me2Si)2(η5-C5H4)2NbH3] (3), which is prone to decomposition within a few days at room temperature both in solution and in the solid-state, thus affording primarily an insoluble black material. However, after heating or irradiation of a solution of 3 small quantities of the dimeric niobium hydride species, [(Me2Si)2{μ-(η1:η5-C5H3)}(η5-C5H4)NbH]2 (4), were isolated and characterized by X-ray diffraction.