Bulky Formamidinate-Supported Lanthanoid Halides and Alkyls, Including a Rare Terminal La–Me Species

The oxidation of [Sm(DippForm) 2 (thf) 2 ] ( 1; DippFormH = N,N ′-bis(2,6-diisopropylphenyl)formamidine) by tert -butyl chloride, 1,2-dibromoethane, and iodine, respectively, at ambient temperature led to the isolation of the light yellow crystalline samarium(III) halide complexes [Sm(DippForm) 2 X(thf)] ( 2, X = Cl; 3, X = Br; 4, X = I) in good yield. The subsequent metathesis reaction of [Ln(DippForm) 2 X(thf)] ( 2, Ln = Sm, X = Cl; Ln = La, X = F) with LiMe and LiCH 2 SiMe 3 generated the samarium alkyl complexes [Sm(DippForm) 2 R(thf)] ( 5, R = Me; 6, R = CH 2 SiMe 3 ) and the rare terminal La–Me complex [La(DippForm) 2 Me(thf)] ( 7 ). The attempted ligand exchange reaction of 7 with 1,2,3,4-tetraphenylcyclopentadiene gave, unexpectedly, the homoleptic tris(formamidinato)lanthanum complex [La(DippForm) 3 ] ( 8 ) in very low yield. The redox transmetalation/protolysis (RTP) reaction from samarium metal with bis(2-bromo-3,4,5,6-tetrafluorophenyl)mercury and DippFormH in thf yielded the mono(formamidinato)samarium(III) complex [Sm(DippForm)Br 2 (thf) 3 ] ( 9 ) as a coproduct with the bis(formamidinate) 3 . Redox reaction of the divalent samarium complex [Sm(DippForm) 2 (thf) 2 ] ( 1 ) with diphenylmercury resulted in the ethenolate complex [Sm(DippForm) 2 (OCH═CH 2 )(thf)] ( 10 ) instead of the target Sm–Ph complex, the product resulting from the decomposition of Lewis base thf molecules.