Synthesis of niobocene imido cations: X-ray crystal structure of [Nb(double bond; length as m-dashNBut)(η5-C5H4SiMe3)2(CNBut)][BPh4]

The reduction of [Nb(double bond; length as m-dashNBut)(η5-C5H4SiMe3)2Cl] by sodium amalgam followed by oxidation by [Fe(η5-C5H5)2][BPh4] in the presence of CNBut gave [Nb(double bond; length as m-dashNBut)(η5-C5H4SiMe3)2(CNBut)][BPh4] (1). In a similar manner, [Nb(double bond; length as m-dashNPh)(η5-C5H4SiMe3)2(CNBut)][BPh4] (2), [Nb(double bond; length as m-dashNPh)(η5-C5H4SiMe3)2(CO)][BPh4] (3) and [Nb(double bond; length as m-dashNBut){Me2Si(η5-C5Me4)(η5-C5H4)}(CNBut)][BPh4] (4), were prepared. The reduction of [Nb(double bond; length as m-dashNBut){Me2Si(η5-C5H4)2}Cl] gave, depending on the experimental conditions, either the d1–d1 dimer [(Nb{Me2Si(η5-C5H4)2}(μ-NBut))2] (5) or the hydride derivative [Nb(double bond; length as m-dashNBut){Me2Si(η5-C5H4)2}H] (6). The reaction of 5 with I2 led to the formation of [Nb(double bond; length as m-dashNBut){Me2Si(η5-C5H4)2}I] (7). The molecular structure of 1 was determined by single-crystal X-ray diffraction studies.