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Book ChapterDOI

Rare Earth Pincer Complexes: Synthesis, Reaction Chemistry, and Catalysis

01 Jan 2015-pp 93-177
TL;DR: The research field surrounding rare earth pincer complexes has reached a stage where a comprehensive review about the reactivity and catalytic behavior of these species is justified as mentioned in this paper, and several types of compounds are discussed, including extremely reactive hydrides, cationic species, and intriguing scandium imido complexes.
Abstract: The research field surrounding rare earth pincer complexes has reached a stage where a comprehensive review about the reactivity and catalytic behavior of these species is justified. In this contribution, we begin with a brief introduction on common strategies for the preparation of rare earth pincer complexes, continuing with a section devoted to the versatile reactivity observed for this class of compound. Thereafter, several types of compounds are discussed, including extremely reactive hydrides, cationic species, and intriguing scandium imido complexes. Finally, the last portion of this chapter sums up the hitherto reported catalytic studies, including discussions on ring-opening polymerization of cyclic esters, polymerization of olefins and hydroamination reactions, as well as several examples of more infrequently encountered catalytic processes.
Citations
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Journal ArticleDOI
TL;DR: In this paper, the authors present an overview of the history of homogeneous catalysis and its application in alkenes, including the following: 1.1. Introduction. 2.2.
Abstract: Preface.- Acknowledgements.- 1: Introduction.- 1.1. Catalysis. 1.2. Homogeneous catalysis. 1.3. Historical notes on homogeneous catalysis. 1.4. Characterization of the catalyst. 1.5. Ligand effects. 1.6. Ligands according to donor atoms. 2: Elementary Steps.- 2.1. Creation of a 'vacant' site and co-ordination of the substrate. 2.2. Insertion versus migration. 2.3. beta-Elimination and de-insertion. 2.4. Oxidative addition. 2.5. Reductive elimination. 2.6. alpha-Elimination reactions. 2.7. Cycloaddition reactions involving a metal. 2.8. Activation of a substrate toward nucleophilic attack. 2.9. sigma-Bond metathesis. 2.10. Dihydrogen activation. 2.11. Activation by Lewis acids. 2.12. Carbon-to-phosphorus bond breaking. 2.13. Carbon-to-sulfur bond breaking. 2.14. Radical reactions. 3: Kinetics.- 3.1. Introduction. 3.2. Two-step reaction scheme. 3.3. Simplifications of the rate equation and the rete-determining step. 3.4. Determining the selectivity. 3.5. Collection of rate data. 3.6. Irregularities in catalysis. 4: Hydrogenation.- 4.1. Wilkinson's catalyst. 4.2. Asymmetric hydrogenation. 4.3. Overview of chiral bidentate ligands. 4.4. Monodentate ligands. 4.5. Non-linear effects. 4.6. Hydrogen transfer. 5: Isomerisation.- 5.1. Hydrogen shifts. 5.2. Asymmetric isomerisation. 5.3. Oxygen shifts. 6: Carbonylation of Methanol and Methyl Acetate.- 6.1. Acetic acid. 6.2. Process scheme Monsanto process. 6.3. Acetic anhydride. 6.4. Other systems. 7: Cobalt Catalysed Hydroformylation.- 7.1. Introduction. 7.2. Thermodynamics. 7.3. Cobalt catalysed processes. 7.4. Cobalt catalysed processes for higher alkenes. 7.5. Kuhlmann cobalt hydroformylation process. 7.6. Phosphine modified cobalt catalysts: the shell process. 7.7. Cobalt carbonyl phosphine complexes. 8: Rhodium Catalysed Hydroformylation.- 8.1. Introduction. 8.2. Triphenylphosphine asthe ligand. 8.3. Diphosphines as ligands. 8.4. Phosphites as ligands. 8.5. Diphosphites. 8.6. Asymmetric hydroformylation. 9: Alkene Oligomerisation.- 9.1. Introduction. 9.2. Shell-higher-olefins-process. 9.3. Ethene trimerisation. 9.4. Other alkene oligomerisation reactions. 10: Propene Polymerisation.- 10.1. Introduction to polymer chemistry. 10.2. Mechanistic investigations. 10.3. Analysis by 13CNMR spectroscopy. 10.4. The development of metallocene catalysts. 10.5. Agostic interactions. 10.6. The effect of dihydrogen. 10.7. Further work using propene and other alkenes. 10.8. Non-metallocene ETM catalysts. 10.9. Late transition metal catalysts. 11: Hydrocyanation of Alkenes.- 11.1. The adiponitrile process. 11.2. Ligand effects. 12: Palladium Catalysed Carbonylations of Alkenes.- 12.1. Introduction. 12.2. Polyketone. 12.3. Ligand effects on chain length. 12.4. Ethene/propene/CO terpolymers. 12.5. Stereoselective styrene/CO terpolymers. 13: Palladium Catalysed Cross-Coupling Reactions.- 13.1. Introduction. 13.2. Allylic reaction. 13.3. Heck reaction. 13.4. Cross-coupling reaction. 13.5. Heteroatom-carbon bond formation. 13.6. Suzuki reaction. 14: Epoxidation.- 14.1. Ethene and propene oxide. 14.2. Asymmetric epoxidation. 14.3. Asymmetric hydroxilation of alkenes with osmium tetroxide. 14.4. Jacobsen asymmetric ring-opening of epoxides. 14.5. Epoxidations with dioxygen. 15: Oxydation with Dioxygen.- 15.1. Introduction. 15.2. The Wacker reaction. 15.3. Wacker type reactions. 15.4. Terephthalic acid. 15.5. PPO. 16: Alkene Metathesis.- 16.1. Introduction. 16.2. The mechanism. 16.3. Reaction overview. 16.4. Well-characterised tungsten and molybdenum catalysts. 16.5. Ruthenium catalysts. 16.6. Stereochemistry. 16.7. Catalyst decomposition. 16.8. Alkynes. 16.9. Industrial applications. 17: Enantioselective Cyclopropanation.-

263 citations

Journal ArticleDOI
TL;DR: In this article, the neutral 2,7-di-tert-butyl-4,5-bis(diisopropylphosphino)-9,9-dimethylthioxanthene (iPrxanPSP) pincer ligand and several Ru complexes thereof were synthesized.
Abstract: Iridium complexes bearing PCP-type pincer ligands are the most effective catalysts reported to date for the low-temperature (≤ca. 200 °C) dehydrogenation of alkanes. To investigate the activity of formally isoelectronic ruthenium complexes, we have synthesized the neutral 2,7-di-tert-butyl-4,5-bis(diisopropylphosphino)-9,9-dimethylthioxanthene (iPrxanPSP) pincer ligand and several Ru complexes thereof. The (iPrxanPSP)Ru complexes catalyze alkane transfer dehydrogenation of the benchmark cyclooctane/t-butylethylene (COA/TBE) couple with turnover frequencies up to ca. 1 s–1 at 150 °C and 0.2 s–1 at 120 °C, the highest rates for alkane dehydrogenation ever reported at such temperatures. Dehydrogenation of n-octane, however, is much less effective. A combination of experiment and DFT calculations allow us to explain why (iPrxanPSP)Ru is more effective than (iPrPCP)Ir for dehydrogenation of COA, while the reverse is true for dehydrogenation of n-alkanes. Considering only in-cycle species and simple olefin comp...

26 citations

Journal ArticleDOI
Jie Zhang1, Ting Liu1, Qiang-Qiang Ma1, Shujun Li1, Xuenian Chen1 
TL;DR: The C-S bond cleavage of the thiolato ligand of [2,6-(tBu2PO)2C6H3]NiSCH2Ph (1) mediated by BH3·THF is reported, which would initiate further studies on the transition metal catalyzed borane mediated C- S bond activation of mercaptans.
Abstract: C-S bond activation of thiophenols and mercaptans is of great importance but has rarely been reported In this paper we report the C-S bond cleavage of the thiolato ligand of [2,6-(tBu2PO)2C6H3]NiSCH2Ph (1) mediated by BH3·THF The treatment of 1 with an excess amount of BH3·THF in THF at room temperature afforded the borohydride complex [2,6-(tBu2PO)2C6H3]Ni(η2-BH4) (2) as the only product The reaction of 1 with 2 equiv of BH3·THF in THF at room temperature for 48 h produced the hydride complex [2,6-(tBu2PO)2C6H3]NiH (3) and the mercapto complex [2,6-(tBu2PO)2C6H3]NiSH (5) As a new complex, 5 was also independently synthesized by a salt metathesis reaction of the corresponding chloride complex with NaSH and fully characterized by multinuclear NMR, FTIR, HRMS, X-ray crystallography and elemental analysis A possible mechanism for the formation of 5 was proposed It was supposed that 5 formed through BH3 mediated C-S bond cleavage of the thiolato ligand of 1 The result would initiate further studies on the transition metal catalyzed borane mediated C-S bond activation of mercaptans

17 citations

Journal ArticleDOI
TL;DR: It was found that the mercapto groups are difficult to be deprotonated by boron hydrides or organic bases.
Abstract: Several pincer ligated nickel mercapto complexes, [2,6-(R2 PCH2 )2 C6 H3 ]NiSH (R=tBu, 1 a; iPr, 1 b), [2,6-(R2 PO)2 C6 H3 ]NiSH (R=tBu, 2 a; iPr, 2 b) and [4-MeOCO-2,6-(tBu2 PO)2 C6 H2 ]NiSH (3 a), were synthesized and fully characterized. The reactivity of the mercapto groups against boron hydrides and organic bases was investigated. It was found that the mercapto groups are difficult to be deprotonated by boron hydrides or organic bases. The treatment of complex 2 a or 2 b with an excess amount of catecholborane (HBcat) afforded the corresponding pincer ligated nickel borohydride complexes and the HBcat degradation product. The treatment of complex 1 a, 2 a or 2 b with an excess amount of BH3 ⋅THF produced the corresponding nickel borohydride species and the S-bridged triborane species THF⋅BH2 -μ2 -S(B2 H5 ) (5). No reactions between these complexes and organic bases were observed. DFT calculations were carried out to understand this reactivity and get mechanistic insights into the reactions.

16 citations

Journal ArticleDOI
TL;DR: Remarkably, the nucleophilic attack of the pyrazolyl at the silicon atom and concomitant Si−H‐bond cleavage is restricted to the tetravalent cerium oxidation state and appears to proceed via the formation of a transient cerium(IV) hydride, which engages in immediate redox chemistry.
Abstract: The cerium(IV) pyrazolate complexes [Ce(Me2 pz)4 ]2 and [Ce(Me2 pz)4 (thf)] initiate β-hydride abstraction of the bis(dimethylsilyl)amido moiety, to afford a heteroleptic cerium(IV) species containing a dimethylpyrazolyl-substituted silylamido ligand, namely [Ce(Me2 pz)3 (bpsa)] (bpsa=bis((3,5-dimethylpyrazol-1-yl)dimethylsilyl)amido; Me2 pz =3,5-dimethylpyrazolato), along with some cerium(III) species. Remarkably, the nucleophilic attack of the pyrazolyl at the silicon atom and concomitant Si-H-bond cleavage is restricted to the tetravalent cerium oxidation state and appears to proceed via the formation of a transient cerium(IV) hydride, which engages in immediate redox chemistry. When [Ce(Me2 pz)4 ]2 is treated with [Li{N(SiMe3 )2 }], that is, in the absence of the SiH functionality, any redox chemistry did not occur. Instead, the ceric ate complex [LiCe2 (Me2 pz)9 ] and the stable mixed-ligand ceric species [Ce(Me2 pz)2 {N(SiMe3 )2 }2 ] were obtained.

7 citations

References
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Journal ArticleDOI
TL;DR: This work focuses on the characterization of the phytochemical components of Lactide ROP and their role in the regulation of cell reprograming.
Abstract: 23 Stereocontrol of Lactide ROP 6164 231 Isotactic Polylactides 6164 232 Syndiotactic Polylactides 6166 233 Heterotactic Polylactides 6166 3 Anionic Polymerization 6166 4 Nucleophilic Polymerization 6168 41 Mechanistic Considerations 6168 42 Catalysts 6169 421 Enzymes 6169 422 Organocatalysts 6169 43 Stereocontrol of Lactide ROP 6170 44 Depolymerization 6170 5 Cationic Polymerization 6170 6 Conclusion and Perspectives 6171 7 Acknowledgments 6173 8 References and Notes 6173

2,014 citations

Journal ArticleDOI
TL;DR: Hydroamination of Alkenes and Alkynes under Microwave Irradiation and Nitromercuration Reactions 3878 9.8.4.5.
Abstract: 8.4.5. Nitromercuration Reactions 3878 9. Hydroamination of Alkenes and Alkynes under Microwave Irradiation 3878 * To whom correspondence should be addressed. Phone: +49 241 8

1,685 citations

Book
01 Jan 1988
TL;DR: General Properties of Organometallic Complexes The Metal-Carbon and Metal-Hydrogen Bonds Ligand Substitution Reactions Complexes of Pi-Bound Ligands Oxidative Addition and Reductive Elimination Insertion and Elimination Nucleophilic and Electrophilic Additions and Abstraction Homogeneous Catalysis Characterization of OO Compounds Carbenes, Metathesis and Polymerization The Activation of Small Molecules Clusters and the Metal-Metal Bond Applications to Organic Synthesis Oxidation and High-Oxidation-State
Abstract: General Properties of Organometallic Complexes The Metal-Carbon and Metal-Hydrogen Bonds Ligand Substitution Reactions Complexes of Pi-Bound Ligands Oxidative Addition and Reductive Elimination Insertion and Elimination Nucleophilic and Electrophilic Addition and Abstraction Homogeneous Catalysis Characterization of Organometallic Compounds Carbenes, Metathesis and Polymerization The Activation of Small Molecules Clusters and the Metal-Metal Bond Applications to Organic Synthesis Oxidation and High-Oxidation-State Complexes Bioorganometallic Chemistry Solutions to Problems.

1,651 citations

Journal ArticleDOI
TL;DR: This review discusses the synthetic methodologies that are currently available for the preparation of platinum group metal complexes containing pincer ligands and especially emphasizes different applications that have been realized in materials science such as the development and engineering of sensors, switches, and catalysts.
Abstract: Since the first reports in the late 1970s on transition metal complexes contain- ing pincer-type ligands—named after the particular coordination mode of these ligands—these systems have at- tracted increasing interest owing to the unusual properties of the metal centers imparted by the pincer ligand. Typical- ly, such a ligand comprises an anionic aryl ring which is ortho,ortho-disubsti- tuted with heteroatom substituents, for example, CH2NR2 ,C H 2PR2 or CH2SR, which generally coordinate to the met- al center, and therefore support the MC s bond. This commonly results in a terdentate and meridional coordina- tion mode consisting of two metalla- cycles which share the MC bond. Detailed studies of the formation and the properties of a large variety of pincers containing platinum group metal complexes have provided direct access to both a fundamental under- standing of a variety of reactions in organometallic chemistry and to a range of new applications of these complexes. The discovery of alkane dehydrogenation catalysts, the mecha- nistic elucidation of fundamental transformations (for example, CC bond activation), the construction of the first metallodendrimers for sustain- able homogeneous catalysis, and the engineering of crystalline switches for materials processing represent only a few of the many highlights which have emanated from these numerous inves- tigations. This review discusses the synthetic methodologies that are cur- rently available for the preparation of platinum group metal complexes con- taining pincer ligands and especially emphasizes different applications that have been realized in materials science such as the development and engineer- ing of sensors, switches, and catalysts.

1,413 citations