A series of Ln(III) tris(benzhydryl) complexes [(p-tBu-C 6 H 4) 2 CH] 3 Ln (Ln = La (1), Nd (2), Y (3)) were synthesized by the salt metathesis reactions of LnHal 3 (THF) 3.5 (Ln = La, Nd, Hal = Cl; Ln = Y, Hal = I) and [(p-tBu-C 6 H 4) 2 CH]Na. In 1-3 the benzhydryl ligands are linked with the metal centres in η 4-coordination mode. For diamagnetic complexes 1 and 3 a fluxional behaviour was detected in solution. Complexes 1-3 proved to be thermally stable: no decomposition was observed even after heating their solutions in toluene-d 8 at 140°C during 72 h. The reactions of 1 and 2 with B(C 6 F 5) 3 allowed for the synthesis of base-free cationic complexes [(p-tBu-C 6 H 4) 2 CH] 2 Ln[(p-tBu-C 6 H 4) 2 CHB(C 6 F 5) 3 ] (Ln = La (4), Nd (5)) which adopt the structure of a contact ion pair. Combinations of 1-3 and borane ((B(C 6 F 5) 3 , [Me 2 NHPh][B(C 6 F 5) 4 ], [Ph 3 C][B(C 6 F 5) 4 ]) as well as 4 and 5 were found to be highly efficient, regio-and chemoselective catalysts for hydroarylation and hydrobenzylation of C=C bonds of a variety of substrates with substituted pyridines. These catalysts enable highly challenging transformations such as hydrobenzylation of 1,1-disubstituted and internal C=C bonds.
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