Permethylated transition-metal complexes,as represented by neutral M(CH_3)_x and anionic [M(CH_3)_y]~(n-),have attracted considerable interest not only for displaying the simplest truly organometallic derivatives but also for their intrinsic bonding phenomena.While structural and theoretical investigations have led to enormous progress for thermally labile homoleptic Group 4,5,6,and 7 derivatives,monometallic Group 3 and lanthanide congeners have remained elusive.For example,the synthesis of rare-earth-metal-alkyl complexes such as LnEt_3 (Ln=Sc,Y) was claimed as early as 1938,however,striking evidence of their existence,be it spectroscopic data or clarifying follow-up chemistry,has never been reported.Moreover,the ease of beta-hydride elimination in such early transition-metal-alkyl complexes led to controversial discussions.
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