Polymeric dimethylytterbium and the terminal methyl complex (Tp^tBu,Me)Yb(CH₃)(thf)

Abstract

Divalent ytterbium bis(trimethylsilyl)amides [Yb{N(SiMe3)2}2]2 and Yb[N(SiMe3)2]2(thf)2 react with purified methyllithium to amorphous dimethylytterbium [YbMe2]n. The characterisation was performed by 171Yb and 13C CP/MAS NMR spectroscopy as well as by conducting...

Rare Earth Starting Materials and Methodologies for Synthetic Chemistry

“… 503 The Sm analogue [Sm{N(SiMe 3 ) 2 } 2 (THF) 2 ] ( 78-Sm ·2THF) was obtained by Evans and co-workers with similar methodologies using [Sm(I) 2 (THF) 2 ] and Na[N(SiMe 3 ) 2 ]. 288 78-Yb can also be synthesized via (1) RT reaction of Yb metal with [Sn{N(SiMe 3 ) 2 } 2 ], 90 (2) RTP reaction of Yb metal with HgPh 2 and HN(SiMe 3 ) 2 , 162 and (3) protonolysis between Yb(Bn) 2 (Bn = CH 2 Ph) and HN(SiMe 3 ) 2 504 ( Scheme 52 ; see section 3.4 for details on RT and RTP methods). All these alternative methods are highly desirable to avoid the presence of alkali metal or halide impurities.…”

“…Salt metathesis reactivity is the most common methodology employed for the synthesis of binary alkyl and aryl complexes ( Scheme 66 , A ), though there are some notable exceptions such as (1) RT reactions with organomercurials and organobismuth reagents for the synthesis of aryl complexes ( Scheme 66 , B ; vide supra , section 3.4 ), 12 (2) donor cleavage reactions from organoaluminate precursors ( Scheme 66 , C ), 631 and (3) transmetalation reactions between amide precursors and MeLi ( Scheme 66 , D ). 504 Saran and co-workers reported the reaction of MeLi and PhLi with RECl 3 (Sc, Y, La, and Pr) in 1970. 632 In the case of reactivity with PhLi, the authors identified Sc(Ph) 3 and Y(Ph) 3 via IR spectroscopy and elemental analysis, though with La and Pr they identified the formation of “ate” complex LiLa(Ph) 4 from analogous reactivity.…”

“… 640 Finally, Anwander and co-workers reported the synthesis and reactivity of the neutral methyl complex [Yb(Me) 2 ] n ( 230 ), which is the only example of methyl derivative with a divalent Ln; 230 was obtained via transmetalation reaction between bis-silylamide precursors and MeLi. 504 …”

“… 639 As would be expected, 230 is also an excellent protonolysis reagent and reacts smoothly with HTp tBu,Me ( Scheme 68 ) to give the terminal methyl complex [Yb(Tp tBu,Me )(Me)(THF)] ( 234 ). 504 …”

“… 714 − 716 Additionally, direct activation of metals is a synthetic technique that is still used by only a few groups around the world, largely because of the historic involvement of toxic Hg and Tl reagents; however, these methods have now been extended to more benign metals (Bi and Ag), 175 which should encourage research teams to incorporate these methods into their synthetic repertoire. Many of the limitations that historically frustrated the progress of RE synthetic chemistry are gradually being challenged and overcome; an example of this is the successful stabilization and identification of the once elusive “RE(Me) 3 ” species by Anwander and co-workers, 504 , 631 , 633 though this still has not been achieved with the larger Lns. 717 Finally, several of the synthetic precursors presented in this work have emerged over the past decade; therefore, because of these recent discoveries, there will certainly be many new and exciting synthetic avenues that will be opened-up in the years to come.…”