The first structurally characterized cationic lanthanide–alkyl complexesElectronic supplementary information (ESI) available: experimental and spectroscopic details. See http://www.rsc.org/suppdata/cc/b2/b201613n/

Reaction of rare earth metal-alkyl complexes [Ln(CH2SiMe3)3(THF)2](Ln = Y, Lu) with B(C6X5)3(X = H, F) in the presence of crown ethers gives crystallographically characterized ion pairs [Ln(CH2SiMe3)2(CE)(THF)n]+[B(CH2SiMe3)(C6X5)3]-(CE = [12]-crown-4, n = 1; CE = [15]-crown-5 and [18]-crown-6, n = 0).