Binuclear and mononuclear di-η⁵-cyclopentadienylniobium chemistry: a new insight. Crystal and molecular structure of [Cp2NbH2]^-[Na · benzo-15-crown-5]⁺

Abstract A mononuclear di-η 5 -cyclopentadienylniobium complex Cp 2 NbH 2 Na (I) has been found to be a by-product of the reaction of Cp 2 NbCl 2 with NaH, the principal products being (η 5 : η 1 -C 5 H 4 ) 2 Cp 2 Nb 2 H 2 ) 2 (II) in THF and (η 5 : η 5 -C 5 H 4 C 5 H 4 )Cp 2 -Nb 2 (η-H) 2 (III) in DME. Cp 2 NbH 2 Na wasalso obtained by reaction of Cp 2 NbH 3 or the mixture of Cp 2 NbBH 4 + Et 3 N with NaH. Crystal and molecular structure of [Cp 2 NbH 2 ] − [Na · NbH 2 − [Na · B15C5] + (Ia) (B15C5 = benzo-15-crown-5) was established by an X-ray diffraction study (4208 reflections, R = 0.022; monoclinic, at −120° C, a 17.345(3), b 11.742(3), c 22.965(5) A, β 98.52(1)°, Z = 8 space group C 2/ c ). The structural data indicate substantial ionic character of the (Cp 2 NgH 2 ) − … (Na · B15C5) + interaction in the solid.