Syntheses and crystal structures of the d0,1,2 metallepins [NbR2(η-C5H5)2][BF4], [NbR2(η-C5H5)2], and [Na(18-crown-6)(thf)2][NbR2(η-C5H5)2](thf = tetrahydrofuran); reduction product of [ZrR2(η-C5H5)2][R2=(o-CH2C6H4)22–]

Abstract

Reaction of [Nb{(o-CH₂C₆H₄)₂}(η-C₅H₅)₂](1) with AgBF₄ gives [Nb{(o-CH₂C₆H₄)₂}(η-C₅H₅)₂][BF₄](2) and with Na[C₁₀H₈] in the presence of 18-crown-6, [Na(18-crown-6)(thf)₂]-[Nb{(o-CH₂C₆H₄)₂}(η-C₅H₅)₂](3)(thf tetrahydrofuran), whereas reduction of [Zr{(o-CH₂C₆H₄)₂}(η-C₅H₅)₂] results in a Zr–CH₂cleavage; single crystal X-ray structure determinations on (1), (2), and (3), show a considerable variation in Nb–CH₂–C and CH₂–Nb-CH₂ angles, and in the torsion along the biphenyl axis, the angular changes at the niobium being in accordance with M.O. predictions [CH₂–Nb–CH₂, 106.3(1)°(d°); 83.0°(d¹); 80(1)(d²)].