A Structural Investigation of Heteroleptic Lanthanide Substituted Cyclopentadienyl Complexes

The substituted cyclopentadienyl group 1 transfer agents KCp′′, KCp′′′ and KCptt (Cp′′ = {C5H3(SiMe3)2-1,3}–; Cp′′′ = {C5H2(SiMe3)3-1,2,4}–; Cptt = {C5H3(tBu)2-1,3}–) were prepared by modification of established procedures and the structure of [K(Cp′′)(THF)]•THF (1) was obtained. KCp′′ and KCptt were reacted variously with [Ln(I)3(THF)4] (Ln = La, Ce) in 2 : 1 stocihiometries to afford monomeric [La(Cp′′)2(I)(THF)] (2a•THF) and the dimeric complexes [La(Cp′′)2(μ-I)]2 (2a), [Ce(Cp′′)2(μ-I)]2 (2b) and [Ce(Cptt)2(μ-I)]2 (3). KCp′′′ was reacted with [Ce(I)3(THF)4] to afford the mono-ring complex [Ce(Cp′′′)(I)2(THF)2] (4), regardless of the stoichiometric ratio of the reagents. Complex 4 was reacted with [KN(SiMe3)2] to yield [Ce(Cp′′’)2(I)(THF)] (5), [Ce(Cp′′′){N(SiMe3)2}2] (6) and [Ce{N(SiMe3)2}3] by ligand scrambling. Complexes 1-6 have all been structurally authenticated and are variously characterised by other physical methods.