Aspects of Divalent Rare-earth-metal Alkyl and Amide Chemistry - read free eBook in online reader or directly download on the web page. Select files or add your book in reader. Download and read online ebook Aspects of Divalent Rare-earth-metal Alkyl and Amide Chemistry write by Markus Katzenmayer. This book was released on 2023. Aspects of Divalent Rare-earth-metal Alkyl and Amide Chemistry available in PDF, EPUB and Kindle. Defined metalmethyl compounds were first reported in the middle of the 19th century and the interest in metal alkyls is still growing. So far 26 out of 60 non-radioactive metals have been found to form homoleptic isolable methyl componds [M(CH3)x] (x = 1-6). The report on the successful synthesis of dimethylcalcium [CaMe2]n triggered further research on the often discussed parallels of alkaline-earth metals and the divalent rare-earth-metals Sm2+, Eu2+ and Yb2+. Dimethylytterbium [YbMe2]n could be accessed via the reaction of the donor-free precursor [Yb{N(SiMe3)2}2]2 with methyllithium. [YbMe2]n was fully characterized and follow-up chemistry was investigated. Noteworthily, the protonolysis reaction of [YbMe2]n with protic hydrotris(3-tBu-5-Me-pyrazolyl)borate HTptBu,Me gave the first terminal Yb2+ methyl complex [TptBu,MeYb(CH3)(thf)] providing direct evidence of the existence of the methyl precursor. Further, the synthesis of the divalent dimethyl compounds of samarium and europium was attempted. The focus of the second part of this work was the synthesis of new rare-earth-metal imide complexes. Through a one-pot salt-metathesis reaction (LnI2(thf)2 + KTptBu,Me + KNHR with Ln = Sm, Eu, Yb and R = 2,6-iPr-C6H3, 2,6-Me-C6H3, 3,5-CF3-C6H3, SiPh3) or a protonolysis approach (TptBu,MeYb(N(SiMe3)2) + H2NR, R = R = 2,6-iPr-C6H3, 3,5-CF3-C6H3, SiPh3) efficient access to amide complexes [TptBu,MeYbNH(R)(thf)x] (R = 2,6-iPr-C6H3, 2,6-Me-C6H3, 3,5-CF3-C6H3, SiPh3) could be gained. All synthesized complexes were fully characterized and their reactivity toward Lewis acids and bases as well as their redox chemistry was further investigated. The obtained compounds are potential precursor complexes for the synthesis of rare-earth-metal imide complexes.
Nitrogen Donor Ligands in the Coordination Chemistry of the Rare Earth and Alkaline Earth Metals
Nitrogen Donor Ligands in the Coordination Chemistry of the Rare Earth and Alkaline Earth Metals - read free eBook in online reader or directly download on the web page. Select files or add your book in reader. Download and read online ebook Nitrogen Donor Ligands in the Coordination Chemistry of the Rare Earth and Alkaline Earth Metals write by Jelena Jenter. This book was released on 2010-05-27. Nitrogen Donor Ligands in the Coordination Chemistry of the Rare Earth and Alkaline Earth Metals available in PDF, EPUB and Kindle. Bis(phosphinimino)methanide rare earth metal bisborohydrides, as illustrated in Scheme I, were successfully synthesized by salt metathesis reactions of [K{CH(PPh2NSiMe3)2}] with [Ln(BH4)3(THF)n] (Ln = Sc (n = 2); Ln = La, Nd, Lu (n = 3)) or in the case of yttrium by the reaction of [{(Me3SiNPPh2)2CH}YCl2]2 with NaBH4. Interestingly, the BH4- anions are ?3-coordinated in the solid state structures of 3, 4, 6 and 7, while for the scandium complex 5 two different conformational polymorphs were identified, in which either both BH4- groups are ?3-coordinated or one BH4- anion shows an ?2-coordination mode. Furthermore, complexes 3, 6 and 7 showed high activities in the ring-opening polymerization (ROP) of e-caprolactone (CL). At 0 °C, the molar mass distribution reached the narrowest values ever obtained for the ROP of CL initiated by a rare earth metal borohydride species. In collaboration with N. Meyer, rare earth metal chlorides and borohydrides of the 2,5-bis{N-(2,6-diisopropylphenyl)iminomethyl}pyrrolyl ligand were synthesized, as shown in Scheme II. The reaction of [(DIP2pyr)K] (10) with anhydrous neodymium trichloride afforded [(DIP2pyr)NdCl2(THF)]2 (12) which is dimeric in the solid state. Excitingly, the reaction of [(DIP2pyr)K] (10) with [Ln(BH4)3(THF)n] (Ln = Sc (n = 2); Ln = La, Nd, Lu (n = 3)) depends on the ionic radii of the center metals. For the larger rare earth metals lanthanum and neodymium, the expected products [(DIP2pyr)Ln(BH4)2(THF)2] (Ln = La (13), Nd (14)) were obtained; while for the smaller rare earth metals scandium and lutetium, an unusual redox reaction of a BH4- anion with one of the Schiff-base functions of the ligand was observed and the products [{DIP2pyr*-BH3}Ln(BH4)(THF)2] (Ln = Sc (15), Lu (16)) were formed (Scheme II). Moreover, the two neodymium containing complexes 12 and 14 were investigated as Ziegler-Natta catalysts for the polymerization of 1,3-butadiene to form poly-cis-1,4-butadiene, by using various cocatalyst mixtures. Very high activities and good selectivities were observed for 12. The 2,5-bis{N-(2,6-diisopropylphenyl)iminomethyl}pyrrolyl ligand was successfully introduced into the coordination chemistry of the divalent lanthanides and the alkaline earth metals. As shown in Scheme III, salt metathesis reactions of [(DIP2pyr)K] (10) with either anhydrous lanthanide diiodides or alkaline earth metal diiodides afforded the corresponding heteroleptic iodo complexes [(DIP2pyr)LnI(THF)3] (Ln = Sm (19), Eu (20), Yb (21)) or [(DIP2pyr)MI(THF)n] (M = Ca (24), Sr (22) (n = 3); Ba (23) (n = 4)). Surprisingly, all complexes 19-24 are monomeric in the solid state, independently from the ionic radii of their center metals. Instead of forming dimers, the coordination sphere of each metal center is satisfied by additionally coordinated THF molecules, which is a very rare structural motif in the chemistry of the larger divalent lanthanides and alkaline earth metals. While the (DIP2pyr)- ligands in 19-23 are ?3-coordinated in the solid state, for the calcium complex 24 an ?2-coordination mode was observed (Scheme III). Interestingly, the calcium complex 24 and the analogous ytterbium compound 21 show different structures in the solid state. In order to obtain catalytically active species, [(DIP2pyr)M{N(SiMe3)2}(THF)2] (M = Ca (25), Sr (26)) were prepared by the reaction of [(DIP2pyr)MI(THF)3] (M = Ca (24), Sr (22)) with [K{N(SiMe3)2}] (Scheme IV). Compounds 25 and 26 were investigated for the intramolecular hydroamination of aminoalkenes and one aminoalkyne. Unfortunately, both catalysts exhibit a limited reaction scope, caused by the formation of undesired side products by alkene isomerization and imine-enamine tautomerism. However, both compounds are active catalysts and show high yields and short reaction times. The highest activities were observed for the calcium complex 25 and can be compared to the results obtained with the ß-diketiminato calcium amide [{(DIPNC(Me))2CH}Ca{N(SiMe3)2}(THF)] as a catalyst. Finally, imidazolin-2-imide and cyclopentadienyl-imidazolin-2-imine rare earth metal alkyl complexes, synthesized by M. Tamm et al., were investigated for the intramolecular hydroamination of non-activated aminoalkenes and one aminoalkyne. Both compounds showed high selectivities and activities, and although they cannot compete with the metallocene analogues, the imidazolin-2-imide complexes are new and interesting examples for catalytically active post-metallocenes.
Metal Amide Chemistry
Metal Amide Chemistry - read free eBook in online reader or directly download on the web page. Select files or add your book in reader. Download and read online ebook Metal Amide Chemistry write by Michael Lappert. This book was released on 2008-12-23. Metal Amide Chemistry available in PDF, EPUB and Kindle. Written by internationally recognised leaders in the field, Metal Amide Chemistry is the authoritative survey of this important class of compounds, the first since Lappert and Power’s 1980 book “Metal and Metalloid Amides.” An introduction to the topic is followed by in-depth discussions of the amide compounds of: alkali metals alkaline earth metals zinc, cadmium and mercury the transition metals group 3 and lanthanide metals group 13 metals silicon and the group 14 metals group 15 metals the actinide metals Accompanied by a substantial bibliography, this is an essential guide for researchers and advanced students in academia and research working in synthetic organometallic, organic and inorganic chemistry, materials chemistry and catalysis.
Expanding Synthetic Aspects of Redox and Mechanical Organometallic Chemistry of Rare Earth Complexes
Expanding Synthetic Aspects of Redox and Mechanical Organometallic Chemistry of Rare Earth Complexes - read free eBook in online reader or directly download on the web page. Select files or add your book in reader. Download and read online ebook Expanding Synthetic Aspects of Redox and Mechanical Organometallic Chemistry of Rare Earth Complexes write by Christopher Matthew Kotyk. This book was released on 2015. Expanding Synthetic Aspects of Redox and Mechanical Organometallic Chemistry of Rare Earth Complexes available in PDF, EPUB and Kindle. This dissertation describes the synthesis, characterization, and reactivity of organometallic complexes of yttrium and the lanthanides in an effort to more completely understand the nature of a recently-discovered class of +2 ions of these rare earth metals. The reactivity of complexes of a new set of Ln2+ ions (Ln = rare earth metal) with unprecedented 4fn5d1 electron configurations has been explored to expand the unique chemistry possible with the rare earth elements. The isolation of unexpected reaction products is described as well as the discovery of a new divalent lanthanide system and the utilization of solvent-free mechanochemical synthesis for established rare earth organometallic species. In Chapter 1, the reactivity of the highly-reducing, air-, moisture-, and temperature-sensitive divalent lanthanide complexes [K(2.2.2-cryptand)][Cp'3Ln] (Ln = Y, La, Ce, Dy) is characterized by examining reactions with aromatic organic substrates of known reduction potential. Complexes of the 4fn5d1 Ln2+ ions reduce naphthalene and biphenyl within minutes to form a new class of reduced aromatic complexes, [K(2.2.2-cryptand)][Cp'2Ln(n4-C10H8)] (Ln = Y, La, Ce, Dy) and [K(2.2.2-cryptand)][Cp'2Y(n6-C6H5Ph)], respectively. The naphthalene reactions also produced the previously unobserved ligand redistribution products [K(2.2.2-cryptand)][Cp'4Ln] (Ln = Y, La), which show the effect of the lanthanide contraction on structure as the lanthanum complex has four n5-Cp' rings while yttrium has three n5-Cp' rings and one n1-Cp' ring.
Advancing the Field of Rare-earth Formamidinate Chemistry
Advancing the Field of Rare-earth Formamidinate Chemistry - read free eBook in online reader or directly download on the web page. Select files or add your book in reader. Download and read online ebook Advancing the Field of Rare-earth Formamidinate Chemistry write by Werner Daniel. This book was released on 2014. Advancing the Field of Rare-earth Formamidinate Chemistry available in PDF, EPUB and Kindle. The work presented in this thesis discusses the formation and behaviour of a variety of different ArForm rare-earth complexes using five ArForm ligands of varied functionalities (N,N'-bis(Aryl)Formamidine: Aryl = 2,6-difluorophenyl (DFFormH), 2,6-diisopropylphenyl (DippFormH), 4-methyl phenyl (p-TolFormH), and 2-trifluoromethylphenyl). In addition the chemistry of rare-earth 3,5-dimethylpyrazolate (Me2pz) complexes is also discussed. The majority of divalent rare-earth ArForm complexes known have been synthesised by redox transmetallation protolysis (RTP) protocols or salt metathesis in THF. Chapter two examines two different synthetic approaches to form divalent rare-earth N,N'-bis(2,6-difluorophenyl)formamidinate DFForm complexes. Initially complexes were generated by the RTP method utilising three different solvent media (THF, PhMe, and Et2O), where the oxidation state of the resulting complex was dependent on the solvent used. Additionally treatment of DFFormH with Ln0 metals in CH3CN proved to be an effective synthetic route to divalent DFForm complexes for both Eu and Yb. However, when the direct metal synthetic method was extrapolated to the bulky DippForm ligand system, results were varied. Although the reactivity of divalent [Sm(DippForm)2(thf)2] has been studied under a variety of conditions (Scheme 1.6), currently the isostructural ytterbium analogue ([Yb(DippForm)2(thf)2]), has only been treated with halogenating oxidants.[58f] Chapter Three investigates the ability for the DippForm ligands to stabilise metal ketyl complexes generated by treating [Yb(DippForm)2(thf)2] with a variety of different aromatic ketones and 1,2-diketones. Through a single electron redox process, a variety of ketyl complexes was generated and showed interesting structures and reactivity.Although divalent and trivalent ArForm complexes are known, tetravalent species have remained an unexplored area. Chapter Four discusses the synthesis and oxidation of five novel cerium(III) ArForm complexes by trityl chloride, leading to transient cerium(IV) species that were prone to rapid decomposition. A cerium(IV) ArForm complex was successfully generated by an alternative method, namely protolysis reactions between ArFormH and tetravalent cerium silylamides. Some of the work presented in this Chapter has been recently published and these publications are in Appendix A and Appendix B.In the final chapter on ArForm ligands, Chapter Five, the coordination of N,N'-bis(2-trifluoromethylphenyl)formamidinate to rare-earth ions is discussed. It was initially hypothesised that the CF3 group would coordinate to the rare-earth metal centre and then undergo C-F activation to produce rare-earth heteroleptic fluoride complexes. However, surprisingly, the CF3 group underwent complete de-fluorination, producing inorganic fluorides and also poly(trifluoromethylphenyl)amidines. This unexpected result is discussed in terms of the conditions of activation along with the role of the rare-earth element. Chapter Six ventures away from the chemistry of rare-earth formamidinates and discusses the chemistry of rare-earth 3,5-dimethylpyrazolate complexes in terms of structures and their peculiar reactivity, where it appears that these complexes have a high affinity to form oxide cages. Part of this work has been recently published and is presented in Appendix C. Across these Chapters the versatility of rare-earth formamidinate complexes has been demonstrated, with new binding modes to rare-earths identified, new synthetic methods determined, different types of reactivity investigated, and the results have opened the doors to much exciting new chemistry.
