β‐Diketiminato Rare‐Earth Metal Complexes: The Influence of Monoatomic Substituents in the N‐aryl Moieties on Structures and Properties

Abstract

Treatment of β‐diketiminate ligands bearing different N‐aryl monoatomic substituents [HLH = (C6H5)N = C(Me)CH=C(Me)NH(C6H5), HLF = (2,6‐F2C6H3)N=C(Me)CH=C(Me)NH(2,6‐F2C6H3), and HLCl = (2,6‐Cl2C6H3)N=C(Me)CH=C(Me)NH(2,6‐Cl2C6H3)] with Ln(CH2SiMe3)3(THF)2 (Ln = Y and Lu) afforded a variety of β‐diketiminato rare‐earth metal complexes depending on substituents, namely, phenyl ring C–H bond activated complexes (L')(LH)Lu(THF) (1b, L' = (C6H4)N = C(Me)CH=C(Me)N(C6H5)), six‐coordinate homoleptic complexes (LH)3Ln [Ln = Y (1aa), Lu (1bb)], five‐coordinate monoalkyl complexes (LF)2Ln(CH2SiMe3) [Ln = Y (2a), Lu (2b)], and four‐coordinate dialkyl complexes (LCl)Ln(CH2SiMe3)2 [Ln = Y (3a), Lu (3b)]. All these complexes were characterized with NMR spectroscopy, and lutetium complexes 1b, 1bb and 3b were structurally validated by single‐crystal X‐ray diffraction analysis. Moreover, dialkyl complexes 3 promoted the polymerization of 2‐vinylpyridine (2‐VP) to produce atactic poly(2‐vinylpyridine) (P2VP) with quantitative yield. On activation with an equimolar amount of [Ph3C][B(C6F5)4], complexes 3 afforded highly isotactic P2VP with an mm value up to 94 %. Both 1H NMR spectrum and MALDI‐TOF mass analysis of an oligomer indicate that the polymerization was initiated by coordination insertion of 2‐VP into the Y‐CH2SiMe3 bond.

Stereoselective Polymerization of Aromatic Vinyl Polar Monomers

“…However, the polymers by asymmetric complexes 60 and 61 were atactic under the same conditions. After adjusting the substituents to chlorine atoms, the resulting complexes 62 and 63 showed a slight decrease in the isoselectivity for 2‐VP polymerization under organoboron salt activation ( mm =94 % or 91 %) (Table 5, Runs 5 and 6) [23] …”

Theoretical investigations of 2-vinylpyridine stereoselective polymerization catalyzed by cationic yttrium complexes with different ancillary ligands

“…In 2018, Cui and colleagues 8 demonstrated that β-diketiminato yttrium complexes [ L 1 Y(CH 2 SiMe 3 )(THF)] + [ L 1 = (2,6-Et 2 C 6 H 3 )NC(Me)CHC(Me)N(2,6-Et 2 C 6 H 3 )] ( Y-1 ) and [ L 2 Y(CH 2 SiMe 3 )(THF)] + [ L 2 = (2,6-Cl 2 C 6 H 3 )NC(Me)CHC(Me)N(2,6-Cl 2 C 6 H 3 )] ( Y-2 ) were effective in catalyzing the polymerization of 2-vinylpyridine (2VP) to produce isotactic polymers. But their analogue [ L 3 Y(CH 2 SiMe 3 )(THF)] + [ L 3 = (2,6-C 6 H 5 )NC(Me)CHC(Me)N(2,6- i Pr 2 C 6 H 3 )] ( Y-3 ) yielded atactic polymers under identical conditions (Scheme 1).…”

Halogenated β‐diketiminato magnesium complexes: Preparation, characterization, and catalysis for ring‐opening polymerization of aliphatic lactones

“…In the previous work, we have reported the influence of the halogen substituents on the structures of β-diketiminato rare-earth metal complexes. 50 To explore the halogenated β-diketiminate ligands with other metals, herein, we presented a series of halogenated β-diketiminato magnesium complexes and their catalytic performances for the ROP of aliphatic lactones.…”

“…We envisioned that the introduction of electron‐withdrawing halogen substituents could increase the Lewis acidity of metal center, facilitate the coordination of monomer, and enhance the catalytic activity. In the previous work, we have reported the influence of the halogen substituents on the structures of β‐diketiminato rare‐earth metal complexes 50 . To explore the halogenated β‐diketiminate ligands with other metals, herein, we presented a series of halogenated β‐diketiminato magnesium complexes and their catalytic performances for the ROP of aliphatic lactones.…”