Facile, aprotic degradation of η5-CpZrCl3·dme by ternary sodium/group 14 tert-butoxides: From η5-CpZrCl3·dme back to NaCp in two easy steps

CpZrCl3·dme was treated with Na[El(OtBu)3], El = Ge, Sn, Pb, respectively. The addition of Na[Sn(OtBu)3] to CpZrCl3·dme caused rapid cyclopentadienide loss and the equally rapid appearance of CpSnCl, half of which crystallized as the trinuclear complex {[ZrCl(OtBu)3]2·CpSnCl}. Pristine CpSnCl reacted almost instantly with NaOtBu to give NaCp and Na[Sn(OtBu)3], which co-crystallized as a coordination polymer. Na[Ge(OtBu)3] also displaced Cp from zirconium, but with a different product distribution, giving Cp2Ge, fac-[Ge(μ-tBuO)3ZrCl(OtBu)2], and ZrCl(OtBu)3. By contrast, Na[Pb(OtBu)3] only exchanged its tert-butoxide groups with zirconium to furnish CpZr(OtBu)3 and PbCl2. The solid-state structures of {[ZrCl(OtBu)3]2·CpSnCl}, fac-[Ge(μ-tBuO)3ZrCl(OtBu)2], and {NaCp·Na[Sn(OtBu)3]}n were determined.

The ambient-temperature reaction of CpZrCl3·dme with NaSn(OtBu)3 yields CpSnCl, which when treated with NaOtBu affords NaCp. The reaction sequence constitutes the synthesis of NaCp from a transition metal η5-Cp complex under extremely mild conditions.Figure optionsDownload as PowerPoint slideHighlights
► NaEl(OtBu)3, El = Ge, Sn, instantly displace Cp ion from CpZrCl3 at RT.
► Cyclopentadienide is recovered as Cp2Ge or CpSnCl.
► CpSnCl reacts with NaOtBu to furnish NaSn(OtBu)3 and NaCp.
► NaPb(OtBu)3 reacts with CpZrCl3 to yield CpZr(OtBu)3.