Imino- and Amido-Pyridinate d-Block Metal Complexes in Polymerization/Oligomerization Catalysis

Giambastiani, Giuliano; Luconi, Lapo; Kuhlman, Roger L.; Hustad, Phillip D.

doi:10.1007/978-90-481-3815-9_5

Cited by 8 publications

(1 citation statement)

References 159 publications

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“…In this regard it appears that metal-to-ligand alkyl migrations on either oxazolinyl or thiazolyl moieties (having more than one coordinative site on equivalent positions and free to switch their coordination mode) preferentially occur through selective heterocycle ring-openings instead of undergoing the more classical imino-group reductions . If alkyl metal-to-ligand migrations on pyridine and imine-based ligands are rather common with a number of main group, transition, and rare-earth metals, processes like those described for the benzothiophene- or the oxazolinyl-containing systems are rather rare instead. ,, …”

Section: Resultsmentioning

confidence: 99%

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

et al. 2014

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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 ...

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Section: Resultsmentioning

confidence: 99%

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

et al. 2014

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Facing Unexpected Reactivity Paths with Zr^IV–Pyridylamido Polymerization Catalysts

Luconi

Rossin

Tuci

et al. 2011

Chemistry A European J

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This work provides original insights to the better understanding of the complex structure–activity relationship of ZrIV–pyridylamido‐based olefin polymerization catalysts and highlights the importance of the metal‐precursor choice (Zr(NMe2)4 vs. Zr(Bn)4) to prepare precatalysts of unambiguous identity. A temperature‐controlled and reversible σ‐bond metathesis/protonolysis reaction is found to take place on the ZrIV‐amido complexes in the 298–383 K temperature range, changing the metal coordination sphere dramatically (from a five‐coordinated tris‐amido species stabilized by bidentate monoanionic {N,N−} ligands to a six‐coordinated bis‐amido–mono‐amino complexes featured by tridentate dianionic {N−,N,C−} ligands). Well‐defined neutral ZrIV–pyridylamido complexes have been prepared from Zr(Bn)4 as metal source. Their cationic derivatives [ZrIV{N−,N,C−}Bn]+[B(C6F5)4]− have been successfully applied to the room‐temperature polymerization of 1‐hexene with productivities up to one order of magnitude higher than those reported for the related HfIV state‐of‐the‐art systems. Most importantly, a linear increase of the poly(1‐hexene) Mn values (30–250 kg mol−1) has been observed upon catalyst aging. According to that, the major active species (responsible for the increased Mn polymer values) in the aged catalyst solution, has been identified.

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Group IV Organometallic Compounds Based on Dianionic “Pincer” Ligands: Synthesis, Characterization, and Catalytic Activity in Intramolecular Hydroamination Reactions

Luconi

Rossin

Motta

et al. 2013

Chemistry A European J

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Neutral Zr(IV) and Hf(IV) diamido complexes stabilized by unsymmetrical dianionic N,C,N' pincer ligands have been prepared through the simplest and convenient direct metal-induced Caryl-H bond activation. Simple ligand modification has contributed to highlight the non-innocent role played by the donor atom set in the control of the cyclometallation kinetics. The as-prepared bis-amido catalysts were found to be good candidates for the intramolecular hydroamination/cyclization of primary aminoalkenes. The ability of these compounds to promote such a catalytic transformation efficiently (by providing, in some cases, fast and complete substrate conversion at room temperature) constitutes a remarkable step forward toward catalytic systems that can operate at relatively low catalyst loading and under milder reaction conditions. Kinetic studies and substrate-scope investigations, in conjunction with preliminary DFT calculations on the real systems, were used to elucidate the effects of the substrate substitution on the catalyst performance and to support the most reliable mechanistic path operative in the hydroamination reaction.

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Imino- and Amido-Pyridinate d-Block Metal Complexes in Polymerization/Oligomerization Catalysis

Cited by 8 publications

References 159 publications

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

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

Facing Unexpected Reactivity Paths with Zr^IV–Pyridylamido Polymerization Catalysts

Group IV Organometallic Compounds Based on Dianionic “Pincer” Ligands: Synthesis, Characterization, and Catalytic Activity in Intramolecular Hydroamination Reactions

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Imino- and Amido-Pyridinate d-Block Metal Complexes in Polymerization/Oligomerization Catalysis

Cited by 8 publications

References 159 publications

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

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

Facing Unexpected Reactivity Paths with ZrIV–Pyridylamido Polymerization Catalysts

Group IV Organometallic Compounds Based on Dianionic “Pincer” Ligands: Synthesis, Characterization, and Catalytic Activity in Intramolecular Hydroamination Reactions

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Facing Unexpected Reactivity Paths with Zr^IV–Pyridylamido Polymerization Catalysts