Thermally Stable Cationic Bis(benzhydryl) Complexes of EarlyLanthanides (La, Ce, Nd)

A series of base-free Ln(III) tris(benzhydryl)complexes [(p-tBu-C6H4)2CH]3Ln (Ln = La (1), Ce (2), Nd(3)) were synthesized by the salt metathesis reactions ofLnCl3(THF)3.5and [(p-tBu-C6H4)2CH]K. Cerium complex2similarly to the previously published congeners1and3features eta 4-type of coordination of benzhydryl ligands. The reactions ofequimolar amounts of1-3and Bronsted acid [NHEt3][B(C6H5)4]allowed for the synthesis of cationic bis(alkyl) complexes of largelanthanides [{(p-tBu-C6H4)2CH}2Ln(TMEDA)][BPh4] (Ln = La(4), Ce (5), Nd (6)), which were isolated as separated ion pairscontaining one TMEDA molecule coordinated with a Ln ion. Incontrast, the reaction of2with Lewis acid B(C6F5)3affords a base-free cationic complex [{(p-tBu-C6H4)2CH}2Ce][mu-{(p-tBu-C6H4)2CH}B(C6F5)3](7), which adopts the structure of a contact ionpair with mu-eta 1:eta 6-bridging benzhydryl ligand. Cationic complexes4-7proved to be thermally stable: no decomposition was observedeven after heating their solutions in toluene at 80 degrees C for 72 h.

Automated summary

A series of base-free Ln(III) tris(benzhydryl) complexes were synthesized and their reactions with Bronsted and Lewis acids were investigated.