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Divalent (C5Me5)2Sm reacts with AgBPh4 in toluene to form (C5Me5)2SmBPh4, 1, in ca. 60% yield. The solid-state structure of 1 consists of a trivalent (C5Me5)2Sm bent metallocene unit with a 2.702(3) Å 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) Å Sm−C(o-Ph) distances. 1 can also be obtained from reactions of Et3NHBPh4 in arene solvents with the trivalent samarium precursors (C5Me5)2SmCH(SiMe3)2 (>50% yield) and (C5Me5)2Sm(η3-CH2CHCH2) (2) (>95% yield). 1 reacts with LiCH(SiMe3)2 in benzene to produce (C5Me5)2SmCH(SiMe3)2 in over 95% yield. The reaction of 1 with KC5Me5 in benzene constitutes a new synthesis of the sterically crowded complex (C5Me5)3Sm, which is formed in over 90% yield. This reaction provides a convenient way to make (C5Me5)3Ln complexes with lanthanides which do not have a reactive divalent oxidation state. To enhance the ease of preparing (C5Me5)3Ln complexes from LnCl3, an improved synthesis of the allyl precursors (C5Me5)2Ln(η3-CH2CHCH2) (Ln = Sm (2), Nd (3), Tm (4)) is reported. 2−4 can be prepared in 60−90% yield from (C5Me5)2LnCl2K(THF)2 and ClMg(CH2CHCH2) followed by desolvation of the solids between 55 and 70 °C for 4−16 h. 2−4 react with Et3NHBPh4 in benzene to produce (C5Me5)2LnBPh4 (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)2NdCH(SiMe3)2 and (C5Me5)3Nd (7), respectively, in high yield. 7 was characterized by X-ray crystallography and shown to have an (η5-C5Me5)3Nd structure with a 2.86(6) Å Nd−C(C5Me5) distance. Since the allyl complexes (C5Me5)2Ln(η3-CH2CHCH2) are readily converted to the hydrides (C5Me5)2LnHn by hydrogen, the improved synthesis of the allyl complexes also provides an improved route to these hydrides as demonstrated by the reaction of (C5Me5)2Nd(η3-CH2CHCH2) with H2 to form (C5Me5)2NdH2 in 75% yield.
Evans et al. (1998) studied this question.