Thermally Stable Half-Sandwich Benzhydryl Ln(II) (Ln = Sm, Yb) Complexes Supported by Sterically Demanding Carbazolyl and Fluorenyl Ligands

A series of new isolable and thermally stable half-sandwich Ln(II) benzhydryl complexes coordinated by the sterically demanding ligands tert-butylcarbazol-9-yl [tBu(4)Carb]Ln[(p-tBu-C6H4)(2)CH](L) (Ln = Sm, L = DME (4); Ln = Yb, L = DME (5); Ln = Yb, L = TMEDA (6)) and 2,7-di-tert-butyl-fluoren-9-trimethylsilylyl [2,7-tBu(2)-9-Me3Si-C13H6]Yb[(p-tBu-C6H4)(2)CH](DME) (7) were synthesized by the alkane elimination reaction of [(p-tBu-C6H4)(2)CH](2)Ln-(L-n) (Ln = Sm, Yb) with tBu(4)CarbH and 2,7-tBu(2)-9-Me3Si-C13H7. X-ray analysis revealed that in 4, 5, and 7 the benzhydryl ligand is coordinated to the metal ion in an eta(3) coordination mode, while in 6 it is eta(1)-bound. The type of coordination of the benzhydryl ligands in diamagnetic 5-7 is retained in their C6D6 solutions. Complexes 4-7 demonstrated unprecedented thermal stability and do not undergo decomposition after heating their solutions in C6D6 or toluene at 100 degrees C for 72 h. The reactions of [tBu(4)Carb]Ln[(p-tBu-C6H4)(2)CH](DME) (Ln = Sm (4), Ln = Yb (5)) with an excess of DME led to the formation of the symmetrical bis(carbazolyl) complex products [tBu(4)Carb](2)Ln(DME)(4) (Ln = Sm (8), Yb (9)) isolated in the form of separated ion pairs.