Synthesis, Structure, and Catalytic Behavior of Ytterbium Complexes Derived from a Linked Bis(β‐ketoiminato) Ligand

Abstract

Ytterbium complexes supported by a linked bis(β‐ketoiminato) ligand, N,N′‐ethylenebis(benzoylacetoimine) (H2L), were synthesized and their catalytic behavior was explored. The reaction of YbCl3 with 1 equiv. of LLi2 afforded the mononuclear ytterbium chloride LYbCl(THF)2 (1) in high yield. Complex 1 can be used as starting material to prepare β‐ketoiminate‐ytterbium derivatives. Treatment of complex 1 with NaN(SiMe3)2 produced the dimeric ytterbium amide {LYb[N(SiMe3)2]}2 (2), while the similar reaction of complex 1 with NaOAr (ArO = 2, 6‐tBu‐4‐MeC6H2O) led to the mononuclear ytterbium aryloxide LYbOAr(THF) (3). The three complexes were well detected by elemental analysis and single‐crystal X‐ray analysis. It was found that complexes 2 and 3 can initiate the ring‐opening polymerization of ϵ‐caprolactone with moderate activity.

Synthesis and characterization of rare-earth metal complexes supported by a new pentadentate Schiff base and their application in heteroselective polymerization of rac-lactide

“…8l In complex 2, the Yb-OIJsalen) distances of 2.104(2) and 2.132(2) Å, the Yb-NIJsalen) bond lengths of 2.432(3) and 2.389(3) Å, and the Yb-OIJether) bond length of 2.514(2) Å compare well with those in complex 1 when the difference in the ionic radii between Yb and Sc is considered. 21 The Yb-OIJAr) distance of 2.070(3) Å is consistent with the corresponding bond lengths in ethylene-bridged bisIJβ-ketoiminato) ytterbium aryloxide ijCH 2 NCIJMe)-CHCOPh] 2 YbIJOAr)IJTHF)] (2.090(3) Å) 22 and amine-bridged bisIJphenolate) ytterbium aryloxide ijMe 2 NCH 2 CH 2 N{CH 2 -IJ2-O-C 6 H 2 -Bu t 2 -3,5)} 2 ]YbIJOC 6 H 3 -2,6-Pr i 2 )IJTHF) (2.084(6) Å). 8h Complexes 3 and 5 are isomorphous and only the molecular diagram of complex 3 is shown in Fig.…”

“…21 However, the Yb-OIJether) and Y-OIJether) distances of 2.694(4) Å and 2.663(2) Å, respectively, are obviously longer than the Yb-OIJether) bond length in complex 2, reflecting the strong influence of the bulky amido group ijNIJSiMe 3 ) 2 ] on the metal center. The Ln-NIJamide) distances in complexes 6 and 7 are 2.202(5) and 2.245(2) Å, respectively, which are comparable to the corresponding bond lengths in β-ketoiminato ytterbium amides (2.222-2.230 Å) 22,23 and yttrium salen amides, such as IJsalen′)YijNIJSiHMe 2 )]IJTHF) (2.27 Å), 12a IJsalcyc)YijNIJSiHMe 2 )]IJTHF) (2.303(2) Å) 24 and IJsalpren)YijNIJSiHMe…”