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Rare earth metal complexes ligands

Recently, rare-earth metal complexes have attracted considerable attention as initiators for the preparation of PLA via ROP of lactides, and promising results were reported in most cases [94—100]. Group 3 members (e.g. scandium, yttrium) and lanthanides such as lutetium, ytterbium, and samarium have been frequently used to develop catalysts for the ROP of lactide. The principal objectives of applying rare-earth complexes as initiators for the preparation of PLAs were to investigate (1) how the spectator ligands would affect the polymerization dynamics (i.e., reaction kinetics, polymer composition, etc.), and (2) the relative catalytic efficiency of lanthanide(II) and (III) towards ROPs. [Pg.249]

Alkylated rare-earth metal complexes with rare-earth metal centers surrounded exclusively by oxygen donor ligands were reported from facile ligand redistribution processes in 2,6-dimethylphenolate/trialkylaluminum mixtures. As shown in Scheme 29 for the yttrium derivatives Y(0ArMe,II)2[(//-OArMe>H)2AlR2](THF)2 (R= Me, Et), heterobimetallic 1 1-species were ac-... [Pg.196]

The sterically crowded, monoanionic scorpionate ligand tris(3-tert-butyl-5-methylpyrazol-l-yl)borate (Tp,Bll Me) provides a unique environment for the isolation of discrete rare-earth metal complexes with YMe AlMe4) and... [Pg.148]

Zhang, L.X., Suzuki, T., Luo, Y. et al. (2007) Cationic alkyl rare-earth metal complexes bearing an ancillary bis(phosphinophenyl)amido ligand a catalytic system for living cis-1,4-polymerization and copolymerization of isoprene and butadiene. Angewandte Chemie International Edition, 46, 1909. [Pg.354]

This chapter is intended to cover major aspects of the deposition of metals and metal oxides and the growth of nanosized materials from metal enolate precursors. Included are most types of materials which have been deposited by gas-phase processes, such as chemical vapor deposition (CVD) and atomic layer deposition(ALD), or liquid-phase processes, such as spin-coating, electrochemical deposition and sol-gel techniques. Mononuclear main group, transition metal and rare earth metal complexes with diverse /3-diketonate or /3-ketoiminate ligands were used mainly as metal enolate precursors. The controlled decomposition of these compounds lead to a high variety of metal and metal oxide materials such as dense or porous thin films and nanoparticles. Based on special properties (reactivity, transparency, conductivity, magnetism etc.) a large number of applications are mentioned and discussed. Where appropriate, similarities and difference in file decomposition mechanism that are common for certain precursors will be pointed out. [Pg.933]

A variety of bisoxazolinato rare-earth metal complexes such as 30 have been studied with regard to their hydroamination/cyclization catalytic activity [149]. The precatalysts show similar enantioselectivity and only slightly reduced catalytic activity when prepared in situ from [La N(SiMe3)2 3] and the bisoxazoline ligand. In this ligand accelerated catalyst system the highest rates were observed for a 1 1 metal to ligand ratio. [Pg.28]

An interesting organolanthanide-catalyzed reaction which has been studied in recent years is the addition of terminal alkynes to carbodiimides leading to the novel class of ,A -disubstituted propiolamidines. It was found that half-sandwich rare earth metal complexes bearing silylene-linked cyclopentadienyl-amido ligands can act as excellent catalysts in this addition reaction. As illustrated in Scheme 58, a rare earth amidinate species has been confirmed to be a true catalytic species [68]. [Pg.157]

Rare-Earth Metal Complexes of A, A-Bidentate Ligands. 167... [Pg.165]

In 1998, Kempe and coworkers [34] reported the first aminopyridinato rare-earth metal complexes. 4-Methyl-2-[(trimethylsilyl)amino]pyridine(HLl) was utilized in this complex. The reaction of lithiated LI and YCI3 in ether and pyridine led to the ate complex [Y(Ll)4(LiPy)] (Py = pyridine) (1). The complex 1 catalytically mediated a ligand transfer reaction to form [Pd(Ll)2] and [Y(Ll)3(py)] (2) from [Pd(cod)Cl2] (cod = cyclooctadiene). The LI ligand transfer from yttrium to palladium and the regeneration of 1 are significant in the efficient synthesis of the very strained amido palladium complexes (Scheme 2). Lithiated LI underwent a salt metathesis reaction with ScCb, at low temperature in THF, to yield the homoleptic complex [Sc(L1)3] (3) (Scheme 2). 3 is the first reported scandium aminopyridinato complex [35]. [Pg.168]

Investigation of the catalytic activity of anilido-phosphinimine rare-earth metal complexes was exclusively reported by Cui and coworkers. Various anilido-phosphinimine rare-earth metal complexes were synthesized by deprotonation of aniline-phosphinimines II-A with [Ln(CH2SiMe3)3(THF)2] [53]. Interestingly, the deprotonation of II-A was followed by intramolecular C-H activation of the phenyl group on the phosphine moiety to generate dianionic ligands which coordinated to the metal center in a CA A -tridentate mode. The resulting complexes... [Pg.178]

Only a few tris-P-diketiminato rare-earth metal complexes (74,75, and 77) were prepared [64,71,72] and no catalytic activities were reported until Shen and coworkers very recent discovery on synthesis and catalytic applications of such complexes [86], To compare the electronic effects of ligands on the reactivity of their lanthanide complexes, L21 and its derivatives L28 (a methyl electron-donating group at the para-position on the phenyl) and L29 (a chloro electron-withdrawing group at the para-position on the phenyl) were used in the study. LnCb (Ln = Pr, Nd, Sm) and lithium salt of L29 via salt elimination led to [Ln(L29)3] (Ln = Pr (130), Nd (131), Sm (132)). [Nd(L21)3] (133) and [Nd(L28)3] (134) were prepared by the same method shown in Scheme 45. [Pg.193]

The bis(phosphinimino)methanide rare-earth metal complexes are prepared by two general methods salt and amine eliminations. The salt elimination method is more established. To avoid the problem of occlusion of solvated lithium chloride in salt methasesis reactions, the potassium bis(phosphinimino)methanide complex KL30 was used as a ligand transfer reagent. The solvent-free complex KL30 can be easily accessed by the reaction of bis(phosphinimino)methaneHL30 with an excess of KH in THF (Scheme 48) [103]. [Pg.195]

In 1999, An wander et al. synthesized the first rare-earth metal complexes containing bisoxazolinate ligands [132]. Yttrium and lanthanum were chosen as examples for small and large rare-earth metal centers to show the high scope of the synthesis. Both types of complexes, mono-bisoxazolinates and bis-bisoxazolinates. [Pg.210]

In 2003, O Shaughnessy and Scott reported the first example of rare-earth metal complexes supported by biaryl diamide ligands as the catalysts for the hydroamination reactions [159]. A series of C2 symmetric secondary diamine proligands L37-L40 were prepared by arylations of (7 )-2,2 -diamino-6,6 -dimethybiphenyl under palladium catalysis. L37 reacted with complexes [Ln N(SiHMe2)2 3(THF)2] to form the biaryl diamide complexes [Ln(L37) N(SiHMe2)2 (THF)2] (Ln = Y (190), La (191), Sm (192)). Deprotonation... [Pg.216]

Wu and coworkers prepared a new diamide ligand LSI with a CH2SiMc2 bridging unit and a series of rare-earth metal complexes supported by LSI. Diamide complexes [Ln(LSl) N(SiMe3)2 (THF)] (Ln = Y (222), Nd (223), Sm (224), Dy (22S), Yb (226)) were obtained from the reaction of H2LSI with 1 equiv of corresponding rare-earth metal amide complexes [Ln N(SiMc3)2 3( J.-Cl)Li(THF)3] in toluene (Scheme 82) [167]. [Pg.221]

There are only a few studies of siloxides serving as spectator ligands in the chemistry of trivalent rare earth metal complexes. In an attempt to design robust precatalysts for the hydrosilylation of olefins, Okuda etal. prepared several rare earth complexes supported by the siloxide ligand, (Bu 0)3Si0 (Scheme 5). Reaction of [Ln(CH2SiMe3)3(THF) ] (Ln = Y, Tb, Lu) with (Bu 0)3Si0H afforded the dimeric siloxides (26). Addition... [Pg.209]

Rare earth metal complexes witii stericaUy demanding tris(aryl)silyl-substituted binaphtholate ligands efficiently catalyze asymmetric hydroamination/cyclization of aminoalkenes and the kinetic resolution of a-substituted aminopentenes. The catalytic activities are comparable to... [Pg.446]


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See also in sourсe #XX -- [ Pg.240 , Pg.241 , Pg.242 , Pg.243 , Pg.244 , Pg.245 , Pg.246 , Pg.247 ]




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