Unsolvated lanthanide metallocene cations [(C5Me5)2Ln][BPh4]:: Multiple syntheses, structural characterization, and reactivity including the formation of (C5Me5)3Nd

Divalent (C5Me5)(2)Sm reacts with AgBPh4 in toluene to form [(C5Me5)(2)Sm][BPh4], 1, in ca. 60% yield. The solid-state structure of 1 consists of a trivalent (C5Me5)(2)Sm bent metallocene unit with a 2.702(3) Angstrom average Sm-C(C5Me5) distance that is oriented toward two of the phenyl rings of the [BPh4](-) anion with 2.825(3) and 2.917(3) Angstrom Sm-C(o-Ph) distances. 1 can also be obtained from reactions of Et3NHBPh4 in arene solvents with the trivalent samarium precursors (C5Me5)(2)Sm[CH(SiMe3)(2)] (> 50% yield) and (C5Me5)(2)Sm(eta(3)-CH2CHCH2) (2)(> 95% yield). 1 reacts with LiCH(SiMe3)(2) in benzene to produce (C5Me5)(2)Sm[CH- (SiMe3)(2)] in over 95% yield. The reaction of 1 with KC5Me5 in benzene constitutes anew synthesis of the sterically crowded complex (C5Me5)(3)Sm, which is formed in over 90% yield. This reaction provides a convenient way to make (C5Me5)(3)Ln complexes with lanthanides which do not have a reactive divalent oxidation state. To enhance the ease of preparing (C5Me5)(3)Ln complexes from LnCl(3), an improved synthesis of the allyl precursors (C5Me5)(2)Ln(eta(3)-CH2CHCH2) (Ln = Sm (2), Nd (3), Tm (4)) is reported. 2-4 can be prepared in 60-90% yield from (C5Me5)(2)LnCl(2)K(THF)(2) and ClMg(CH2CHCH2) followed by desolvation of the solids between 55 and 70 degrees C for 4-16 h. 2-4 react with Et3NHBPh4 in benzene to produce [(C5Me5)(2)Ln][BPh4] (Ln = Sm (1), Nd (5), Tm (6)). 5 has a solid-state structure identical to that of 1 and similarly reacts with LiCH(SiMe3)(2) and KC5Me5 in benzene to produce (C5Me5)(2)Nd[CH(SiMe3)(2)] and (C5Me5)(3)Nd (7), respectively, in high yield. 7 was characterized by X-ray crystallography and shown to have an (eta(5)-C5Me5)3Nd structure with a 2.86(6) Angstrom Nd-C(C5Me5) distance. Since the allyl complexes (C5Me5)(2)Ln(eta(3)-CH2CHCH2) are readily converted to the hydrides [(C5Me5)(2)LnH](n) by hydrogen, the improved synthesis of the allyl complexes also provides an improved route to these hydrides as demonstrated by the reaction of (C5Me5)(2)Nd(eta(3)-CH2CHCH2) with H-2 to form [(C5Me5)(2)NdH](2) in 75% yield.