C₃-Symmetric Chiral Organolanthanide Complexes:  Synthesis, Characterization, and Stereospecific Polymerization of α-Olefins

Abstract

The trialkyl complexes [M(iPr-trisox)(CH2SiMe2R)3] (R = Me, M = Y, (1), R = Ph, M = Lu (2a), R = Me, M = Lu (2b), Tm (3), Er (4), Ho (5), and Dy (6)) were prepared from 1,1,1-tris[(S)-4-isopropyloxazolinyl]ethane (iPr-trisox) and the corresponding trialkyl precursors [M(CH2SiMe2R)3(THF) n ]. Their molecular structures all display a highly distorted octahedral geometry, with the angles subtended at the metal center significantly deviating from the ideal 90°, which is attributed to the steric demands imposed by the large CH2SiMe2R ligands, both with each other and with the isopropyl groups of the iPr-trisox ligand. Active catalysts for the polymerization of α-alkenes (n-hexene, n-heptene, and n-octene) were generated in situ by reaction of the trialkyl precatalyst with 2 equiv of trityl tetrakis(pentafluorophenyl)borate. In all cases polyolefins with M w/M n values of between 1.58 and 2.08 and isotacticities of 80−95% were obtained. The polymerization activity increases from lutetium to thulium and then subsequently decreases with increasing ionic radius of the metal due to a combination of activation with increasing ionic radius and decreasing catalyst stability.

Piano-Stool Lutetium Amido and Imido Compounds Supported by a Constrained Bis(oxazoline)cyclopentadienyl Ligand

“…The nitrogen ligand is best described as an amidoboryl group. This structure is consistent with the 19 F NMR spectrum that suggested inequivalent C 6 F 5 groups, assuming hindered rotation around N−C 6 F 5 , Lu−C 6 F 5 , and both Lu−N and N−B bonds. The complex is C 1 symmetric in the solid state and crystallizes in the chiral space group Pna2 1 as a single enantiomer, but comes from entirely achiral starting materials.…”

“…18 Interestingly, the Lu1−N1 distance is shorter than the distances in the six-coordinate complex [Lu(iPrtrisox)(CH 2 SiMe 2 Ph) 3 ] of 2.504(3), 2.510(3), and 2.522(3) Å. 19 The Lu1−C29 and Lu1−C22 distances of 2.379(3) and 2.367(3) Å, respectively, for the benzyl ligands are the same within 3σ. These distances are shorter than the Lu−C distances of 2.404(7), 2.408(4), and 2.413(5) Å in the Lu(η 1 - CH 2 Ph) 3 THF 3 starting material.…”

“…The C 6 F 5 plane (defined by C22, C26, and C27) and the C 5 Me 4 planes (defined by C14, C16, and C18) are nearly orthogonal (87.5°). A Lu1−F1 interaction may contribute to the hindered rotation that makes all fluorine in the Lu−C 6 F 5 inequivalent in the 19 In reactions that appear more closely related to the current transformation, B(C 6 F 5 ) 3 reacts with diketiminate scandium or anilido-iminoyttrium dialkyl compounds to give perfluorophenyl rare earth compounds.…”

Four-coordinate erbium organometallic and coordination complexes: Synthesis and structure

“…There are only three other structurally characterized complexes containing an EreCH 2 SiMe 3 bond: Er(CH 2 SiMe 3 ) 3 (THF) 2 [29], Er(CH 2 SiMe 3 ) 3 (THF)(ImMe 2 i Pr 2 ) [30], and Er(CH 2 SiMe 3 ) 3 ( i Prtrisox) [31], all of which are composed of three alkyl ligands and either one or two neutral donors. In comparison to the bond lengths in 3 and 4, these tris(alkyl) erbium complexes exhibit considerably elongated EreC distances ranging from 2.392(3) A e 2.428(3) A.…”

Exploiting Threefold Symmetry in Asymmetric Catalysis: The Case of Tris(oxazolinyl)ethanes (“Trisox”)

“…[35] Upon reducing the polymerisation temperature to À30 8C, the activity dropped to 2030 kg mol À1 h À1 ; however, at this temperature Figure 5). [36] Although the iPr-trisox ligand readily adapts to a wide range of ionic radii, we were unable to successfully prepare complexes with the lanthanides preceding dysprosium, possibly owing to the decreased stability of lanthanide alkyl complexes as the ionic radius increases.…”