X-ray crystal structure of the tetra(tert-butyl)erbate anion and attempts to prepare tetravalent organolanthanide complexes

The new Li(DME)₃⁺] salt of the previously-known tetra(tert-butyl)erbate(III) anion Er(t-Bu)₄⁻] has been prepared and structurally characterized. The erbium(III) center is ligated by four tert-butyl groups in an approximately tetrahedral arrangement. The C–Er–C angles between the tert-butyl groups range from 108.8(3)° to 111.2(3)° and the Er–C distances range from 2.352(6) to 2.395(6) Å. The lithium cation is surrounded by three DME molecules, which form a distorted octahedral coordination sphere. Attempts to oxidize the analogous terbate complex Li(DME)₃]Tb(t-Bu)₄] and its cerium analog to electrically neutral tetra(alkyl)lanthanide(IV) compounds are described.