A Comparative Study on the Reactivity of Tris‐β‐Diketiminate Ytterbium Complexes: Steric Effect of β‐Diketiminato Ligands

Abstract

A series of tris‐β‐diketiminate ytterbium complexes with the general formula [YbL3] {L = [N(C6H5)C(Me)]2CH–, LH (1); [N(4‐MeC6H4)C(Me)]2CH–, L4‐Me (2), and [N(2‐MeC6H4)C(Me)]2CH–, L2‐Me (3)} were synthesized and structurally characterized. All complexes have longer Yb–N bond lengths than other YbL‐containing derivatives, and complex 3 has the longest average Yb–N bond length. A comparative study on the reactivity of complexes 1–3 revealed that complex 3 was a highly active catalyst for the polymerization of ϵ‐caprolactone and L‐lactide, as well as for the addition of amines to carbodiimides, whereas both complexes 1 and 2 were almost inactive under the same conditions. The active sequence is consistent with the distance of the Yb–N bond, which is reflected in the sterically induced activation of the bulky tris‐β‐diketiminate ytterbium complexes.

β‐Diketiminatoytterbium aryloxides: synthesis, structural characterization, and catalytic activity for addition of amines to carbodiimides

“…For example, the yield of the product reached 93% after 1 h when the reaction was conducted with 2‐MeC 6 H 4 NH 2 , whereas the reaction with 2,6‐ i Pr 2 C 6 H 3 NH 2 afforded the corresponding guanidine in 76% yield even with the reaction time extended to 3 h at the same catalyst loading of 0.5 mol% (Table , entries 7 and 13), which may be attributed to steric hindrance. The same phenomenon has also been observed for systems with other lanthanide catalysts reported …”

Synthesis and characterization of β-triketimine cobalt complexes and their behaviour in the polymerization of 1,3-butadiene

“…Data were in accord with those published. 51 Synthesis and characterization of β-triketimines (L) L 1 : HBDK 2,4,6-Me3 (1.86 g, 5.6 mmol) was dissolved in hexane (100 cm 3 ) and the solution was stirred in a Schlenk tube. n BuLi (4 cm 3 of a 1.6 M solution in hexane, 6.4 mmol) was added slowly to the solution through a syringe.…”

Synthesis and Characterization of β-Diketimine Schiff Base Complexes with Ni(II) and Zn(II) Ions: Experimental and Theoretical Study

“…In addition, β-diketiminate anions were applied in lanthanide organometallic and metal-organic chemistry as they are easily accessible and show tunable steric and electronic effects [5,14]. Trisβ-diketiminate ytterbium complexes with various β-ketiminato ligands were examined for their catalytic activity in the ring-opening polymerization of caprolactone and lactide [15] and in the addition of amines to carbodiimides, revealing that the catalytic activity of these coordination complexes is greatly affected by the steric bulk of the β-diketiminato ligands of which the bulkiest was found to be the most active one [16,17].…”