Organolanthanides with 3-(2-pyridylmethyl) indenyl ligands: synthesis, crystal structures and catalytic activities of divalent complexes for ε-caprolactone polymerization

Homolysis of the Ln–N bond: Synthesis, characterization and catalytic activity of organolanthanide(II) complexes with 2-pyridylmethyl and 3-pyridylmethyl-functionalized indenyl ligands

“…It is found that complexes 3-6 with 2-pyridylmethylsubstituted indenyl ligands showed very poor catalytic activity on MMA polymerization (with no more than 1% conversion of monomer in 1 h), these results are similar to those of the THF-coordinated complexes with 2-pyridylmethyl-substituted indenyl ligands [12]. It is of interesting found that the lanthanide(II) complexes 9, 10 and 12 with 3-pyridylmethyl-functionalized indenyl ligands showed moderate to good catalytic activities on MMA polymerization in THF and DME, but they showed very poor catalytic activities when the polymerization procedures were performed in toluene, this phenomenon may be attributed to the poor solubility of the complexes in toluene at low temperatures.…”

“…This distance is shorter than the corresponding values of 2.806(12) Å in [Me 2 Si(Me 2 NCH 2 CH 2 C 9 H 5 )(t-BuNH)] 2 -Yb II [7a], 2.782(8) Å in [g 5 :g 1 -(2-C 5 H 4 NCH 2 )C 9 H 6 ] 2 Yb II (THF) [12], 2.778 (14) Å in (Me 2 NCH 2 CH 2 C 9 H 5 SiMe 3 ) 2 Yb [7a], is close to 2.722(10) Å in (Me 2 NCH 2 CH 2 C 9 H 6 ) 2 Yb [7a]. The average distance of 2.723 (14) Å in 3 is longer than those of 2.683(5) Å , 2.68(1) Å , and 2.68(2) Å found in (Me 2 NCH(Me)CH 2 C 5 H 4 ) 2 Yb [13], Yb(Cp Py ) 2 [14], and Yb(Cp Py(s) ) 2 [14], respectively.…”

“…The average distance of 2.723 (14) Å in 3 is longer than those of 2.683(5) Å , 2.68(1) Å , and 2.68(2) Å found in (Me 2 NCH(Me)CH 2 C 5 H 4 ) 2 Yb [13], Yb(Cp Py ) 2 [14], and Yb(Cp Py(s) ) 2 [14], respectively. The Yb-N distance of 2.561(7) Å in 3 is shorter than the corresponding values of 2.587(7) Å in [g 5 :g 1 -(2-C 5 H 4 NCH 2 )C 9 H 6 ] 2 Yb II (THF) [12], 2.673(11) Å in [Me 2 Si(Me 2 NCH 2 CH 2 C 9 H 5 )(t-Bu-NH)] 2 Yb II , 2.650(12) Å in (Me 2 NCH 2 CH 2 C 9 H 5 SiMe 3 ) 2 -Yb, 2.588(7) Å in (Me 2 NCH 2 CH 2 C 9 H 6 ) 2 Yb [7a], and 2.603(4) Å in (Me 2 NCH(Me)CH 2 C 5 H 4 ) 2 Yb [13]. But, the Yb-N distance of 2.561(7) Å in 3 is longer than those of 2.48(1) Å found in Yb(Cp Py ) 2 [14], and Yb(Cp Py(s) ) 2 [14], respectively.…”

“…The N-Yb-N angle of 106.7(4)°found in 3 is smaller than the corresponding value of 159.8°in [g 5 :g 1 -(2-C 5 H 4 NCH 2 )C 9 H 6 ] 2 Yb II (THF) [12] for different coordination geometry, but the N-Yb-N angle of 106.7(4)°found in 3 is larger than those of 95.1(1)°in [Me 2 Si(Me 2 NCH 2 -CH 2 C 9 H 5 )(t-BuNH)] 2 Yb II , 92.8(5)°in (Me 2 NCH 2 CH 2 C 9 -H 5 SiMe 3 ) 2 Yb, 103.7(2)°in (Me 2 NCH 2 CH 2 C 9 H 6 ) 2 Yb [7a], 103.1(2)°in (Me 2 NCH(Me)CH 2 C 5 H 4 ) 2 Yb [13], 100.8(2)°i n Yb(Cp Py ) 2 , and 84.04(4)°in Yb(Cp Py(s) ) 2 [14] due to steric effects.…”

“…The indene compounds were synthesized by the reactions of lithium indenide with 2-pyridylmethyl or 3-pyridylmethyl chlorides by using the reported procedures with slightly modifications [12]. The silyl-substituted indene compounds were prepared by treatments of 3-(2-C 5 H 4 NCH 2 )C 9 H 7 or 3-(3-C 5 H 4 NCH 2 )C 9 H 7 with n-BuLi, followed by reactions with excess Me 3 SiCl, the synthetic routes were outlined in Schemes 1 and 2.…”