Organolanthanide Complexes Supported by Thiazole-Containing Amidopyridinate Ligands: Synthesis, Characterization, and Catalytic Activity in Isoprene Polymerization

Abstract

Neutral bis(alkyl)-organolanthanide complexes supported by tridentate {N − ,N,N} monoanionic 5-methylthiazole-or benzothiazoleamidopyridinate ligands have been prepared and completely characterized: (L Thia Me 2 )Ln(CH 2 SiMe 3 ) 2 [Ln = Lu 3+ (3), Er 3+ (7), Yb 3+ (8)] and (L BnTh Me 2 )Lu(CH 2 SiMe 3 ) 2 (5). Similarly to related Y 3+ systems, the nature of the thiazole unit controls the ultimate catalyst stability in solution. In the diamagnetic Lu 3+ complex 5, a progressive and complete rearrangement of its metal coordination sphere takes place through a metal-to-ligand alkyl migration with subsequent benzothiazole ring-opening and generation of the Lu 3+ mono(alkyl)-arylthiolate species stabilized by a tetradentate {N − ,N,N,S − } dianionic ligand. On the other hand, the 5-methylthiazolecontaining complexes 3, 7, and 8 showed no evidence of any ligand rearrangement. Complexes 3−8 have been tested as homogeneous catalysts in isoprene (IP) polymerization, after activation with selected organoborates. Binary systems 3/TB and 7/TB [TB = tritylium tetrakis(pentafluorophenyl)borate] show the highest activity and living character toward IP polymerization, affording polymers with relatively high trans-1,4-selectivity (up to 76.4%), moderate molecular weights (M n up to 146 000 g/mol), and narrow polydispersities (M w /M n ). Depending on the rare-earth ion of choice, a prevalent trans-1,4 (Lu 3+ , Er 3+ , Yb 3+ ; up to 76.4%) or a dominant 3,4 (Y 3+ ; 92.7%) polymer structure is observed. The influence of the ligand type, metal ion, and activator(s) on the ultimate catalyst activity and selectivity is discussed. ■ INTRODUCTIONRecent years have witnessed an impressive progress toward the design and synthesis of novel organolanthanides, in light of their ability to promote thermodynamically unfavorable reactions such as hydrocarbon activation 1 and alkane functionalization. 2 A great deal of attention is currently paid to the improvement of the catalytic systems through a finetuning of the stereoelectronic properties of their ancillary ligands, a key tool for controlling and investigating the reactivity, stability, and catalytic performance at the coordinated metal center. The synthesis of tailored ancillary ligands suitable for coordination to rare-earth ions, the isolation of the corresponding alkyl species, and the investigation of their complex structure−reactivity relationship for an optimal catalyst design represent a still challenging area of research in the field of organo-rare-earth chemistry. 3 The exploitation of the catalytic properties of selected single-site organolanthanides for the preparation of polyolefin materials with specific physical, thermal, and mechanical properties deriving from a careful control of their microstructure is still a hot topic in homogeneous catalysis. In particular, the stereospecific polymerization of 1,3-conjugated dienes such as isoprene (IP) is one of the most important industrial processes (surely one of the most investigated in the literature) 4 for the preparation of ...

The crystal structure of tris(μ2-1,3-bis(4,4,4-trifluoro-3-oxido-1-(oxo)but-2-en-1-yl)phenyl-κ4 O,O′:O′′,O′′′)-bis(1,2-dimethoxyethane-κ2 O,O′)dilutetium(III), C50H38F18Lu2O16

“…Lutetium(III) complexes have wide range applications in catalysis in the past few years [4][5][6]. Some directly related structures of the title structure have been reported [3,[7][8].…”

Lanthanides and actinides: Annual survey of their organometallic chemistry covering the year 2014

“…In addition, the electrochemical behavior of Sc 3 C 2 @I h -C 80 was markedly changed by the radical addition, but the absorption spectra of the pristine and the derivative are both featureless. These results suggested that the unpaired electron of The reactions of (µ-H) 3 Re 3 (CO) 11 (NCMe) with Sc 2 @C 82 -C 3v (8), Sc 2 C 2 @C 80 -C 2v (5), Sc 2 O@C 82 -C s (6), C 86 -C 2 (17), and C 86 -C s (16) have been carried out to produce facecapping cluster complexes. The Re 3 triangles were found to bind to the sumanene-type hexagons (cf.…”

“…[103] M a n u s c r i p t The influence of the ligand type, metal ion, and activator(s) on the ultimate catalyst activity and selectivity has been discussed. [11] In a related study, it has been pointed out that precisely controlling the stereochemistry of a copolymerization by a single catalyst, and achieving copolymers with predicted sequences, is often a challenging project in organometallic and macromolecular sciences. In this context it was discovered that the [110]…”

“…N@C80 -I h show no reactivity toward (µ-H)3 Re 3 (CO)11 (NCMe), probably due to electronic and steric factors. These complexes could be easily purified by using HPLC.…”

Imidazole‐Bridged Tetrameric Group(IV) Heteroleptic Complexes from the Spontaneous Metal‐Ligand Assembly of a Potentially N4‐Tetradentate Ligand

“…In recent years, our group has been extensively working on the preparation of multidentate heteroleptic N‐ligands and their related κ 3 {N,N,N}M 3+/4+ coordination compounds (or κ 3 {N,C,N}M 3+/4+ /κ 3 {N,N,C}M 3+/4+ organometallics) based on highly electrophilic metal ions (from group IV elements of the periodic table or from lanthanides, ) for applications in homogeneous catalysis. In a recent report, we have described the synthesis, characterization and catalytic application of a series of Zr IV /Hf IV alkyl/amido complexes stabilized by a tridentate N‐ligand containing a benzoimidazole fragment .…”