Lanthanide Amido Complexes Research Articles

Synthesis and characterization of Bis(β‐diketiminato) rare‐earth amido complexes, their activity for catalytic addition of amines to carbodiimides

Reactions of anhydrous RECl3 (RE = Sm, Nd) with 2 equiv. of NaL2-Me (L2-Me = [N(2-MeC6H4)C(Me)]2CH−) afforded the dimeric chlorides [Sm(L2-Me)2(μ-Cl)]2 (1) and [Nd(L2-Me)2(μ-Cl)]2 (2). Salt metathesis reactions between chloride complexes and NaN(SiMe3)2 in THF yielded a series of bis(β-diketiminato) rare-earth amido complexes RE(L2-Me)2[N(SiMe3)2] (RE = Sm (3), Nd (4), Yb (5), Y (6), Pr (7)). Complexes 1−7 were fully characterized including X-ray single crystal structure analyses. Complexes 3−7 can serve as efficient pre-catalysts for catalytic addition of amines to carbodiimides to afford multi-substituted guanidines. Catalytic activity was influenced by the rare-earth metals with an active sequence of Y (6) ∼ Yb (5) < Pr (7) < Nd (4) < Sm (3). The present catalytic addition reaction using complex 3 showed a wide scope of substrates including primary and secondary aromatic amines and aliphatic cyclic amines. The mechanism investigation by the isolation and characterization of the intermediates of the amido complexes RE(L2-Me)2(NHPh)(THF) (RE = Sm (8), Nd (9), Yb (10)) and guanidinate complexes Sm(L2-Me)2[(C6H5NH)C(NCy)2] (11) and Nd(L2-Me)2[(C6H5N)C(NHCy)(NCy)] (12). Their reactivity revealed that the present catalytic addition proceeded through amine-exchange reaction between the pre-catalyst amido complex and an amine to a novel amido complex, nucleophilic addition of the formed amido species to a carbodiimide to yield a guanidinate species, and protonation reaction of the guanidinate species by an amine to regenerate amido species and release the final product.

Synthesis and Characterization of Bis(Β-Diketiminato) Rare-Earth Amido Complexes, Their Activity for Catalytic Addition of Amines to Carbodiimides and Mechanism Study

Synthesis and Characterization of Bis(Β-Diketiminato) Rare-Earth Amido Complexes, Their Activity for Catalytic Addition of Amines to Carbodiimides and Mechanism Study

Synthesis, Characterization, and Reactivity of Lanthanide Amides Incorporating Neutral Pyrrole Ligand. Isolation and Characterization of Active Catalyst for Cyanosilylation of Ketones

A series of lanthanide amido complexes incorporating a neutral pyrrole ligand were synthesized and characterized, and their catalytic activities were studied. Treatment of [(Me3Si)2N]3Ln(μ-Cl)Li(THF)3 with 1 equiv of [(2,5-Me2C4H2N)CH2CH2] 2NH (1) in toluene afforded the corresponding lanthanide amides with the formula [η5:η1-(2,5-Me2C4H2N)CH2CH2]2NLn[N(SiMe3)2]2 (Ln = La (2), Nd (3)). Reaction of 2 or 3 with N,N′-dicyclohexylcarbodiimide (CyN═C═NCy) gave the carbodiimide selectively inserted into the appended Ln–N bond products formulated as CyNC{[N,N-(2,5-Me2C4H2N)CH2CH2]2N}NCyLn[N(SiMe3)2]2 (Ln = La (4), Nd (5)). Reactions of the lanthanide amides with Me3SiCN were also examined. A mixed reaction of [(Me3Si)2N]3La(μ-Cl)Li(THF)3, [(2,5-Me2C4H2N)CH2CH2]2NH (1), and Me3SiCN in toluene at room temperature produced the novel cyano bridged dinuclear lanthanum complex η5:η1:η3-[(2,5- Me2C4H2NCH2CH2)2N]La[N(SiMe3)2](μ-CN)La[N(SiMe3)2]3 (6). The stoichiometric reactions of lanthanide amides 2 or 3 with Me3SiCN produced the novel trinuclear lanthanum and neodymium complexes {(η5:η1-[(2,5-Me2C4H2NCH2CH2)2N]Ln[N(SiMe3)2](μ-CN)}3 (Ln = La (7), Nd (8)) through selective σ-bond metathesis reaction of the terminal Ln–N (N(SiMe3)2) bond with the Si–C bond of Me3SiCN. On the basis of the stoichiometric reactions of complexes 2, or 3 with Me3SiCN, complexes 2, 3, 4, 5, 7, and 8 as catalysts for cyanosilylation of ketones were investigated. Results indicated that these complexes displayed a high catalytic activity on addition of Me3SiCN to ketones, and the activity of the complexes has the order of 7 ∼ 8 > 2 ∼ 3 ∼ 4 ∼ 5. Thus, complex 7 or 8 was proposed as the active catalyst in the catalytic reaction for the precatalysts of 2 and 3.

Synthesis, structure, and catalytic activity of rare-earth metal amides with a neutral pyrrolyl-functionalized indolyl ligand

The reactions of neutral pyrrolyl-functionalized indole with rare-earth metal amides [(Me3Si)2N]3RE(µ-Cl)Li(THF)3 produced the rare-earth metal complexes [(Me3Si)2N]2RE([η1:µ-η2-3-(2-(N-CH3)C4H3NCH=N-CH2CH2)C8H5N])(µ-Cl)Li(THF) (RE = Er, Y) having indolyl ligand η1 bonded to rare-earth metal ion and η2 bonded to lithium ion. The catalytic activities of these lanthanide amido complexes for addition of terminal alkynes to aromatic nitriles were explored. Results reveal that these complexes displayed a good catalytic activity for the addition reaction under mild conditions.

Synthesis, structure, and catalytic activity of novel trinuclear rare-earth metal amido complexes incorporating μ–η5:η1bonding indolyl and μ3-oxo groups

The reactions of different pyrrolyl-functionalized indoles with rare-earth metal(III) amides [(Me3Si)2N]3RE(III)(μ-Cl)Li(THF)3 (RE = Yb, Er, Dy, Eu, Y) produced different kinds of rare-earth metal amido complexes. Reactions of N-((1H-pyrrol-2-yl)methylene)-2-(1H-indol-3-yl)ethanamine with rare-earth metal amides [(Me3Si)2N]3RE(III)(μ-Cl)Li(THF)3 (RE = Yb, Er, Dy, Eu, Y) in toluene or THF at temperatures of 75-80 °C afforded the novel trinuclear rare-earth metal amido complexes incorporating the indolyl ligand in μ-η(5):η(1) bonding modes and a μ3-O group, which is believed to originate from cleavage of the THF ring based on experimental results. Reactions of 2-(1H-indol-3-yl)-N-((1-methyl-1H-pyrrol-2-yl)methylene)ethanamine with rare-earth metal(III) amides [(Me3Si)2N]3RE(III)(μ-Cl)Li(THF)3 (RE = Yb, Dy) produced mononuclear ytterbium and dysprosium amides having the indolyl ligand in an η(1) bonding fashion. The results indicate that substituents not only have an influence on reactivity, but also have an influence on the bonding of the indolyl ligands with metals. The catalytic activities of the novel lanthanide amido complexes for the hydrophosphonylation of both aromatic and aliphatic aldehydes and ketones were explored. The results indicate that these complexes display a high catalytic activity for the C-P bond formation under mild conditions when using low catalyst loadings (0.1 mol% for aldehydes and ketones). Thus, it provides a potential way to prepare α-hydroxy phosphonates.

Synthesis of γ-amidine-functionalized dianionic β-diketiminato lanthanide amides and trianionic β-diketiminato Na/Sm heterobimetallic complexes and their reactivity in polymerization of l-lactide

The readily accessible dianionic β-diketiminato lanthanide amido complexes LnLN(SiMe3)2(THF) (L = {(2,6-(i)Pr2C6H3)NC(CH2)CHC(CH3)N(2,6-(i)Pr2C6H3)}(2-)) show an unprecedented reactivity toward carbodiimides. The reaction with N,N'-dicyclohexylcarbodiimide (DCC) led via [4 + 2] cycloaddition to γ-amidine-functionalized dianionic β-diketiminato lanthanide amido complexes, LnL(1)N(SiMe3)2 (L(1) = {[(NHC6H11)(NC6H11)C]HC[C(CH2)N(2,6-(i)Pr2C6H3)]2}(2-), Ln = Sm(1), Yb(2), Y(3), Gd(4)). Conversion of a mixture of SmLN(SiMe3)2(THF) and NaN(SiMe3)2 with carbodiimide furnished the heterobimetallic complexes of Sm/Na with a novel amidinate-functionalized trianionic β-diketiminate ligand, [Na(DME)2](μ-L(2))[SmN(SiMe3)2] (L(2) = {[C(N(i)Pr)2]HC[C(CH2)N(2,6-(i)Pr2C6H3)]2}(3-), DME = dimethoxyethane) (5) for N,N'-diisopropylcarbodiimide (DIC) and [Na(DME)3](+)[SmL(3)N(SiMe3)2](-) (L(3) = {[C(NCy)2]HC[C(CH2)N(2,6-(i)Pr2C6H3)]2}(3-)) (6) for DCC. Molecular structures of complexes 1-6 were determined by an X-ray single crystal structure analysis. Complexes 1-4 were found to be highly active initiators of the ring-opening polymerization (ROP) of L-lactide (L-LA). The activity depended on the central metal with the increasing sequence of Yb < Y < Gd < Sm. Notably, the binary 1/BnOH (benzyl alcohol) system exhibited an "immortal" nature and proved able to convert 2000 equivalents of L-LA with up to 100 equivalents of BnOH per initiator. All the polylactides (PLAs) obtained showed monomodal, narrow molar mass distributions (M(w)/M(n) = 1.08-1.13) with the M(n) (average number molar mass) decreasing with increasing amount of BnOH proportionally.

Novel Lanthanide Amides Incorporating Neutral Pyrrole Ligand in a Constrained Geometry Architecture: Synthesis, Characterization, Reaction, and Catalytic Activity

The first series of lanthanide amido complexes incorporating a neutral pyrrole ligand in a constrained geometry architecture were synthesized, and their bonding, reactions, and catalytic activities were studied. Treatment of [(Me3Si)2N]3Ln(μ-Cl)Li(THF)3 with 1 equiv of (N-C6H5NHCH2CH2)(2,5-Me2C4H2N) (1) afforded the first example of bisamido lanthanide complexes having the neutral pyrrole η5-bonded to the metal formulated as [η5:η1-(N-C6H5NCH2CH2)(2,5-Me2C4H2N)]Ln[N(SiMe3)2]2 (Ln = La (2) and Nd (3)). Reaction of [(Me3Si)2N]3Sm(μ-Cl)Li(THF)3 with 2 equiv of 1 produced the complex [η5:η1-(N-C6H5NCH2CH2)(2,5-Me2C4H2N)][η1-(N-C6H5NCH2CH2)(2,5-Me2C4H2N)]]SmN(SiMe3)2 (4). Treatment of 3 with 2 equiv of 1 gave the sandwich neodymium complex [η5:η1-(N-C6H5NCH2CH2)(2,5-Me2C4H2N)]2Nd[η1-(N-C6H5NCH2CH2)(2,5-Me2C4H2N)] (5), in which two neutral pyrroles bonded with metal in an η5 mode. Complex 5 could also be prepared by reaction of [(Me3Si)2N]3Nd(μ-Cl)Li(THF)3 with 3 equiv of 1. Reactivities of the lanthanide bisamido complexes were further investigated. Reaction of complex 2 with pyrrolyl-functionalized imine [2-(2,6-iPr2C6H3N═CH)C4H3NH] afforded a mixed η5-bonded neutral pyrrole and η1-bonded anionic pyrrolyl lanthanum complex [η5:η1-(N-C6H5NCH2CH2)(2,5-Me2C4H2N)]{η1-2-[(2,6-iPr2C6H3)NCH]C4H3N}La[N(SiMe3)2] (6). Reactions of complexes 2 and 3 with pyrrolyl-functionalized secondary amine afforded the mixed η5-bonded neutral pyrrole and the η1-bonded anionic pyrrolyl lanthanide complexes [η5:η1-(N-C6H5NCH2CH2)(2,5-Me2C4H2N)][(η1-2-tBuNCH)C4H3N]2Ln (Ln = La (7), Nd (8)) with dehydrogenation of the secondary amine. Investigation of the catalytic properties of complexes 2–8 indicated that all complexes exhibited a high activity with a high chemo- and regioselectivity on the addition of dialkyl phosphite to α,β-unsaturated carbonyl derivatives. An interesting result was found that 1,2-hydrophosphonylation substrates could be catalytically converted to 1,4-hydrophosphinylation products when the substrates are the substituted benzylideneacetones by controlling the reaction conditions.

Unexpected C–H Bond Activation Promoted by Bimetallic Lanthanide Amido Complexes Bearing a META-Phenylene-Bridged Bis(β-diketiminate) Ligand

Treatment of META-[Na(THF)2]2 (1; META = {[2,6-iPr2C6H3NC(Me)C(H)C(Me)N]−}2-(m-phenylene)] with 1 equiv of {Ln[N(SiMe3)2]2(μ-Cl)(THF)}2 (Ln = Y, Yb) in toluene at 110 °C afforded bimetallic lanthanide amido complexes bridged by a chloride and a phenyl group, {Ln[N(SiMe3)2]}2(META′)(μ-Cl) (Ln = Y (2), Yb (3)), which formed via unexpected C–H bond activation of the arene ring. However, the same reactions carried out in both THF and toluene at room temperature gave the bimetallic lanthanide amido–chloro complexes {Ln[N(SiMe3)2]2}META{Ln[N(SiMe3)2]Cl(THF)} (Ln = Y (4), Yb (5)). When they were heated to 110 °C in toluene, complexes 4 and 5 were converted to complexes 2 and 3 via amine elimination. All of these complexes were confirmed by elemental analysis, FT-IR, and X-ray structure analysis and by NMR analysis in the cases of complexes 1, 2, and 4.

Bimetallic lanthanide amido complexes as highly active initiators for the ring-opening polymerization of lactides

A series of neutral bimetallic lanthanide amido complexes supported by rigid phenylene bridged bis(β-diketiminate) ligands were synthesized, and their catalytic behavior for the polymerization of L-lactide and rac-lactide was explored. The amine elimination reaction of Ln[N(TMS)(2)](3)(μ-Cl)Li(THF)(3) with PARA-H(2), [PARA-H(2) = 2[2,6-(i)Pr(2)C(6)H(3)NHC(Me)C(H)C(Me)N]-(para-phenylene)] in a 2:1 molar ratio in THF at 25 °C afforded the corresponding bimetallic lanthanide amido complexes PARA-{Ln[N(SiMe(3))(2)](2)}(2) [Ln = Nd(1), Sm(2), Y(3)] in high isolated yields. Similar reaction of Nd[N(TMS)(2)](3)(μ-Cl)Li(THF)(3) with META-H(2), [META-H(2) = 2[2,6-(i)Pr(2)C(6)H(3)NHC(Me)C(H)C(Me)N]-(meta-phenylene)] at 90 °C in toluene for about 48 h gave META-{Nd[N(SiMe(3))(2)](2)}(2) (4). Complexes 1-4 were well characterized by elemental analysis, IR spectroscopy, and their definitive structures were confirmed by an X-ray crystal structure analysis. The coordination environment and coordination geometry around the metal atoms are similar in these complexes. Each of the metal atoms is four-coordinated with two nitrogen atoms from the N,N-chelating β-diketiminate unit, and two nitrogen atoms from two (Me(3)Si)(2)N- groups to form a distorted tetrahedron. These complexes can serve as highly active initiators for L-lactide polymerization in toluene. In addition, they also showed high activity towards rac-lactide polymerization in THF at room temperature, giving heterotactic-enriched polymers (P(r) ≈ 0.70), and complex 4 displays obviously higher activity in comparison with complex 1.

Lanthanide Amido Complexes Incorporating Amino-Coordinate-Lithium Bridged Bis(indolyl) Ligands: Synthesis, Characterization, and Catalysis for Hydrophosphonylation of Aldehydes and Aldimines

Two series of new lanthanide amido complexes supported by bis(indolyl) ligands with amino-coordinate-lithium as a bridge were synthesized and characterized. The interactions of [(Me(3)Si)(2)N](3)Ln(III)(μ-Cl)Li(THF)(3) with 2 equiv of 3-(CyNHCH(2))C(8)H(5)NH in toluene produced the amino-coordinate-lithium bridged bis(indolyl) lanthanide amides [μ-{[η(1):η(1):η(1):η(1)-3-(CyNHCH(2))Ind](2)Li}Ln[N(SiMe(3))(2)](2)] (Cy = cyclohexyl, Ind = Indolyl, Ln = Sm (1), Eu (2), Dy (3), Yb (4)) in good yields. Treatment of [μ-{[η(1):η(1):η(1):η(1)-3-(CyNHCH(2))Ind](2)Li}Ln[N(SiMe(3))(2)](2)] with THF gave new lanthanide amido complexes [μ-{[η(1):η(1)-3-(CyNHCH(2))Ind](2)Li(THF)}Ln[N(SiMe(3))(2)](2)] (Ln = Eu (5), Dy (6), Yb (7)), which can be transferred to amido complexes 2, 3, and 4 by reflux the corresponding complexes in toluene. Thus, two series of rare-earth-metal amides could be reciprocally transformed easily by merely changing the solvent in the reactions. All new complexes 1-7 are fully characterized including X-ray structural determination. The catalytic activities of these new lanthanide amido complexes for hydrophosphonylation of both aromatic and aliphatic aldehydes and various substituted aldimines were explored. The results indicated that these complexes displayed a high catalytic activity for the C-P bond formation with employment of low catalyst loadings (0.1 mol % for aldehydes and 1 mol % for aldimines) under mild conditions. Thus, it provides a convenient way to prepare both α-hydroxy and α-amino phosphonates.

Synthesis and Characterization of Organolanthanide Complexes with a Calix[4]-pyrrolyl Ligand and Their Catalytic Activities toward Hydrophosphonylation of Aldehydes and Unactivated Ketones

The alkali metal salt free dinuclear trivalent lanthanide amido complexes (η5:η1:η5:η1-Et8-calix[4]-pyrrolyl){LnN(SiMe3)2}2 (Ln = Nd (2), Sm (3), Gd (4)) were prepared through the silylamine elimination reactions of calix[4]-pyrrole [Et2C(C4H2NH)]4 (1) with 2 equiv of [(Me3Si)2N]3Ln(μ-Cl)Li(THF)3 (Ln = Nd, Sm, Gd) in toluene at 110 °C. The complexes were fully characterized by elemental, spectroscopic, and single-crystal X-ray analyses. Studies on the catalytic activity of the new lanthanide amido complexes revealed that these complexes can be used as efficient catalysts for hydrophosphonylation of aldehydes and unactivated ketones, affording the products in high yields by employing a low catalyst loading (0.1 mol %) at room temperature in a short time (20 min). Noteworthy is that it is the first application of calix[4]-pyrrolyl-supported lanthanide amides as catalysts to catalyze the hydrophosphonylation of aldehydes and unactivated ketones under mild conditions.

Synthesis of ferrocene‐containing N‐aryloxo β‐ketoiminate lanthanide complexes and polymerization of ε‐caprolactone

AbstractThe synthesis, characterization and ε‐caprolactone polymerization behavior of lanthanide amido complexes stabilized by ferrocene‐containing N‐aryloxo functionalized β‐ketoiminate ligand FcCOCH2C(Me)N(2‐HO‐5‐But‐C6H3) (LH2, Fc = ferrocenyl) are described. The lanthanide amido complexes [LLnN(SiMe3)2(THF)]2 [Ln = Nd (1), Sm (2), Yb (3), Y (4)] were synthesized in good yields by the amine elimination reactions of LH2 with Ln[N(SiMe3)2]3(µ‐Cl)Li(THF)3 in a 1:1 molar ratio in THF. These complexes were characterized by IR spectroscopy and elemental analysis, and 1H NMR spectroscopy was added for the analysis of complex 4. The definitive molecular structures of complexes 1 and 3 were determined by X‐ray diffraction studies. Complexes 1–4 can initiate the ring‐opening polymerization of ε‐caprolactone with moderate activity. Copyright © 2011 John Wiley &amp; Sons, Ltd.

Synthesis, structure and catalytic activity of alkali metal-free bent-sandwiched lanthanide amido complexes with calix[4]-pyrrolyl ligands

Simple silylamine elimination reactions of calix[4]-pyrrole [R(2)C(C(4)H(2)NH)](4) (R = Me (1), {-(CH(2))(5)-}(0.5) (2)) with 2 equiv. of [(Me(3)Si)(2)N](3)Ln(μ-Cl)Li(THF)(3) (Ln = Nd, Sm, Dy) in reflux toluene, afforded the novel dinuclear alkali metal-free trivalent lanthanide amido complexes (η(5):η(1):η(5):η(1)-R(8)-calix[4]-pyrrolyl){LnN(SiMe(3))(2)}(2) (R = Me, Ln = Nd (3), Sm (4), Dy (5); R = {-(CH(2))(5)-}(0.5), Ln = Nd (6), Sm(7)). The complexes were fully characterized by elemental analyses, spectroscopic analyses and single-crystal X-ray analyses. X-ray diffraction studies showed that each lanthanide metal was supported by bispyrrolyl anions in an η(5) fashion and along with three nitrogen atoms from N(SiMe(3))(2) and two other pyrroyl rings in η(1) modes formed the novel bent-sandwiched lanthanide amido bridged trivalent lanthanide amido complexes, similar to ansa-cyclopentadienyl ligand-supported lanthanide amides with respect to each metal center. The catalytic activities of these organolanthanide complexes as single component l-lactide polymerization catalysts were studied.

Synthesis and Structural Characterization of Lanthanide Amides Stabilized by an N‐Aryloxo Functionalized β‐Ketoiminate Ligand

AbstractThe synthesis and characterization of dimeric lanthanide amides stabilized by a dianionic N‐aryloxo functionalized β‐ketoiminate ligand are described in this paper. Reactions of 4‐(2‐hydroxy‐5‐tert‐butyl‐phenyl)imino‐2‐pentanone (LH2) with Ln[N(SiMe3)2]3(µ‐Cl)Li(THF)3 in a 1:1 molar ratio in THF gave the dimeric lanthanide amido complexes [LLn{N(SiMe3)2}(THF)]2 [Ln=Nd (1), Sm (2), Yb (3), Y (4)] in good isolated yields. These complexes were characterized by IR spectroscopy, elemental analysis, and 1H NMR spectroscopy in the case of complex 4. The definitive molecular structures of complexes 1, 3, and 4 were determined. It was found that complexes 1 to 4 can initiate the ring‐opening polymerization of L‐lactide.

Mild Amidation of Aldehydes with Amines Mediated by Lanthanide Catalysts

Catalytic amidation of aldehydes with amines is efficiently mediated by homoleptic lanthanide amido complexes, Ln[N(SiMe3)2]3 (Ln = La, Sm, and Y). Amidation reactivity follows the trend: La > Sm approximately Y. These reactions proceed in high yield without added oxidants, bases, and/or heat or light, which are usually required in other catalytic amidation processes. The reaction is demonstrated with a variety of amines, with yields as high as 98% based on amine.

Controlled Syntheses, Characterization, and Reactivity of Neutral and Anionic Lanthanide Amides Supported by Methylene-Linked Bis(phenolate) Ligands

A series of neutral and anionic bis(phenolate) lanthanide amides were synthesized by general metathesis reactions, and their reactivity was explored. Protolytic ligand exchange reactions of MBMPH2 (MBMP = 2,2'-methylene bis(6-tert-butyl-4-methyl-phenolate)) with [Ln{N(TMS)2}2(mu-Cl)(THF)]2 (TMS = SiMe3) afforded the desired bridged bis(phenolate) lanthanide chlorides [(MBMP)Ln(mu-Cl)(THF)2]2 [Ln = Nd (1), Yb (2)] in high isolated yields. These lanthanide chlorides were found to be useful precursors for the synthesis of the corresponding lanthanide derivatives. Reactions of 1 and 2 with 2 equiv of NaN(TMS)2 in THF produced the expected neutral bis(phenolate) lanthanide amido complexes (MBMP)Ln[N(TMS)2](THF)2 [Ln = Nd (3), Yb (4)] in high yields. Whereas the reactions of 1 and 2 with LiN(TMS)2 in a 1:4 molar ratio gave the anionic bis(phenolate) lanthanide amides as discrete ion-pair complexes [Li(THF)4][(MBMP)Ln{N(TMS)2}2] [Ln = Nd (5), Yb (6)] in high isolated yields. Further study revealed that 5 and 6 can also be conveniently synthesized in high yields by the direct reactions of MBMPH2 with [Ln{N(TMS)2}2(mu-Cl)(THF)]2 in a 2:1 molar ratio, and then with 4 equiv of nBuLi. The reactivity of the neutral and anionic bis(phenolate) lanthanide amides was comparatively investigated. It was found that the insertion reactions of carbodiimide into the Ln-N bond of neutral lanthanide amido complexes 3 and 4 gave the anticipated bis(phenolate) lanthanide guanidinate complexes [(mu-O-MBMP)Nd{(iPrN)2CN(TMS)2}]2 (7) and (MBMP)Yb[(iPrN)2CN(TMS)2] (8), respectively, in high yields, whereas the similar reaction of carbodiimide with anionic amido complex 5 provided the unexpected ligand-redistributed products, and the homoleptic ion-pair bis(phenolate) neodymium complex [Li(DME)2(THF)][(MBMP)2Nd(THF)2] (9) was finally isolated as one of the products. Furthermore, the anionic bis(phenolate) lanthanide amides showed higher catalytic activity for the polymerization of epsilon-caprolactone than the neutral ones. All of the complexes were characterized with elemental analysis and IR spectra, and the definitive molecular structures of 1-3 and 5-9 were provided by single-crystal X-ray analyses.

Bis(phosphinimino)methanide Rare Earth Amides: Synthesis, Structure, and Catalysis of Hydroamination/Cyclization, Hydrosilylation, and Sequential Hydroamination/Hydrosilylation

A series of yttrium and lanthanide amido complexes [Ln{N(SiHMe(2))2}2{CH(PPh(2)NSiMe(3))2}] (Ln=Y, La, Sm, Ho, Lu) were synthesized by three different pathways. The title compounds can be obtained either from [Ln{N(SiHMe(2))2}3(thf)2] and [CH(2)(PPh(2)NSiMe(3))2] or from KN(SiHMe(2))2 and [Ln{CH(PPh(2)NSiMe(3))2}Cl(2)]2, while in a third approach the lanthanum compound was synthesized in a one-pot reaction starting from K{CH(PPh(2)NSiMe(3))2}, LaCl3, and KN(SiHMe(2))2. All the complexes have been characterized by single-crystal X-ray diffraction. The new complexes, [Ln{N(SiHMe(2))2}2{CH(PPh(2)NSiMe(3))2}], were used as catalysts for hydroamination/cyclization and hydrosilylation reactions. A clear dependence of the reaction rate on the ionic radius of the center metal was observed, showing the lanthanum compound to be the most active one in both reactions. Furthermore, a combination of both reactions--a sequential hydroamination/hydrosilylation reaction--was also investigated.

N‐Substituted Amido Derivatives of Lanthanides

AbstractThe synthesis of lanthanide amido complexes of the type Ln(CH3CONR)3 (I), (OPri)Ln(C6H5CONC6H5)2 (II), and (OBut)Ln(C6H5CONC6H5)2 (III) [where Ln = La, Pr, Nd; R = C6H5, p‐NO2C6H4, p‐BrC6H4] are described. Infrared spectra indicate deprotonation of the secondary amide (anilide). Anion coordination is proposed as chelating bidenate ligands.