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Design and Synthesis of rare earth organic compounds and the reaction of the carbodiimide

Author: PiChengFu
Tutor: ZhouXiGeng
School: Fudan University
Course: Organic Chemistry
Keywords: With body -based reaction Addition Insertion reaction Rare Earth Metals Carbodiimide Amino compounds Synthesis Crystal structure
CLC: O621.2
Type: PhD thesis
Year: 2007
Downloads: 262
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Abstract


The development of new ancillary ligands to support stoichiometric and catalyticreactivity at metal centers is currently an intensively studied area in organolanthanidechemistry, among which the design of ansa-bridged ligands is an efficient strategy. Inthe first part of our dissertation, synthesis, structural characterization, and reactivity oflanthanide complexes containing the di/trianionic ligands is investigated. The thesismainly focus on investigating the addition of the amino group of organolanthanidederivatives containing the bis-functional ligands to the C=N double bonds ofcarbodiimide to attempt to discover the efficient method for the synthesis of thebridged ligand, providing an alternative the mechanism for small molecular transferwith the organolanthanide-mediated which would be potential in synthesis and designof the more ideal catalyst for guanylation of amine. In addition, the highly selectivereaction of coordinated Cp of the well-known lanthanides Cp3Ln with carbodiimidesis explored. Collectively, we have synthesized sixty-five new complexes, amongwhich fifty three structures were determined through X-ray single crystal diffractionanalysis. This thesis is composed of five chapters. The details are as following:Chapter one, preface, summmaries not only the key role of Cp ligand and itsreactivities with organic small molecules but also the new structure and inspiringreactive natures of the compounds containing the bridged pyrrolyl ligand, and thedevelopment of insertion chemistry of carbodiimides into organometallics is alsointroduced.The second chapter of this dissertation investigates synthesis, structuralcharacterization, and reactivity of lanthanide complexes containing a newmethylene-bridged indenyl-pyrrolyl dianionic ligand or trianionic ligand. A newcarbonous-bridged ligands incorporating both indenyl and pyrrolyl moieties,(C9H7)CHR(α-C4H3NH) (2-1a, R=H; 2-1b, R=nBu) were prepared. Reaction ofLnI2 with one equiv of [(C9H6)CH2(α-C4H3N)]Li2(THF)x in THF, followed byrecrystallization in DME gave the divalent organolanthanide complexes{(η5-C9H6)CH2[μ-η15-(α-C4H3N)]Ln(DME)}2 (Ln=Sm (2-2a), Yb (2-2b)) inmediate yields. Treatment of LnCl3(Ln=Sm, Dy, Er) with one equiv of in situgenerated [(C9H6)CHR(α-C4H3N)]Li2(THF)x (R=H, nBu) in THF under the Similarreaction conditions gave the trivalent organosamarium chloride{(η5-C9H6)CH2[μ-η15-(α-C4H3N)]Sm(μ-Cl)2Li(THF)2}2 (2-3a), [(C9H6)CH2(C4H3N)DyCl2Li(THF)]2 (2-3b), [(η5-C9H6)CH2(μ-η13-C4H3N)Er(μ3-Cl)(μ-Cl)Li(THF)]2 (2-3c), and [(C9H6)CHnBu(C4H3N)SmCl2Li(THF)]2 (2-3d), respectively. Reactionof 2-3a and 2-3b with two equiv of n-Butyllithium (nBuLi) and subsequentlytreatment with CyN=C=NCy and iPrN=C=NiPr respectively, afforded thecarbodiimide insertion into the Sm-C bond product{(η5-C9H6)CH2[μ-η15-(α-C4H3N)]Sm[CyNC(nBu)NCy]}2 (2-4a) and{(η5-C9H6)CH2[μ-η15-(α-C4H3N)]Dy[iPrNC(nBu)NiPr]}2 (2-4b), while treatment of2-3a and 2-3d with 2 equiv of NaN(SiMe32 in THF followed by reacting withCyN=C=NCy gave the carbodiimide insertion into the Sm-N bond product[(η5-C9H7)CH2[μ-η15-(α-C4H3N)]Sm{CyNC[N(SiMe32]NCy}]2 (2-5a) and[(η3-C9H7)CHnBu[μ-η13-(α-C4H3N)]Sm{CyNC[N(SiMe32]NCy}]2 (2-5b). TheLn-N(η15-pyrrolyl) in 2-3a-d showed no reactivity toward carbondiimides. Thereaction of N[CH2(α-C4H3NH)]3 with Ln[N(SiMe32]3 (Ln=Yb, Dy) afforded thecompounds N[CH2(α-C4H3NH)]3Ln(THF)3 (2-6a, Ln=Yb; 2-6b, Ln=Dy), whereLn-N(η1-pyrrolyl) remains intact. The results reveal that this ligand possesses notonly the common features of both moieties but also versatile coordination chemistry,which can coordinate inμ-η155μ-η133 orμ-η135 fashion depending on thenature of the lanthanide metals and substitutes of the bridge with the preferentialformation of cluster speciesThe third chapter is concern with multiple N-H bond activation including synthesisand reactivity of functionalized primary amido mononuclear complexes towardcarbondiimides. A series of new functionalized amido complexes of ytterbium,[Cp2YbNHR]2 (R=8-quinolyl(Qu)(3-1a), 2-pyridyl(Py)(3-1b), 2-aminophenyl(3-1c), 3-amino-2-pyridyl (3-1d) and Cp2Yb[NHC6H4(CH2NH2-2)] (3-1e), have beensynthesized by metathesis of Cp2YbCl and the corresponding amido lithium salts ortreatment of Cp3Yb with the corresponding primary amine. Their reactivity towardcarbodiimides has been investigated, in which multiple N-H activation behavior formetal-bound neutral NH2 and anionic nitrogen-containing fragments, a property thatis expressed without dissociation from the lanthanide center, is observed. Theseresults provide an alternative mechanistic insight for the metal-mediated mono- anddi-guanylation of primary amines, and elucidate factors that affect the chemo- andregioselectivities of the addition and protonation steps. Reaction of 3-1a with 2 equivof RN=C=NR [R=cyclohexyl(Cy), isopropyl(iPr)] leads to the formal insertion ofcarbodiimide into the N-H bond of the Yb-bonded amido group to yieldCp2Yb[η12-RNC(NHR)NQu]2 [R=Cy(3-2a), ipr(3-2b)]. Interestingly, treatment of 3-1b with RN=C=NR affords the unexpected products(Cp2Yb)2[μ-η22-PyNC(NR)2](THF) [R=Cy(3-3a), iPr(3-3b)], representing the firstexample of dianionic guanidinate lanthanide complexes. The reaction of 3-1c withtwo equivalent of RN=C=NR in THF at room temperature leads to the isolation of thesingle N-H addition products Cp2Yb[η1/2-RNC(NHR)NC6H4NH2-2] [R=Cy(3-4a),iPr(3-4b)] in satisfied yields, while treatment of 3-1c with four equiv of RN=C=NRunder the same conditions gives the double N-H addition productsCp2Yb[η12-RNC(NHR)NC6H4{NC(NHR)2-2}] [R=Cy(3-5a), iPr(3-5b)], via theintraligand proton transfer from chelating NH2 to guanidinate group of 3-4 to givenew amido intermediates, followed by a second RN=C=NR insertion into the N-Hbond of the resulting amido groups. Complexes 3-5 can be also obtained by reacting3-4 with 1 equiv of RN=C=NR. The double addition productCp2Yb[η12-CyNC(NHCy)NC5H3N{NC(NHCy)2-3}] (3-6) could be obtained as redcrystals from the 1:4 reaction between 3-1d and CyN=C=NCy in 63% yield.Interestingly, 3-6 can be converted into(Cp2Yb)223-(CyN)2CNC5H3N {NC(NHCy)2-3}] (3-7) under refluxing in THF andwith liberation of a neutral diguanidine C5H3N(NC(NHCy)2)-2,3. A preference of theproton transfer to the second carbodiimide insertion into the N-H bond in theformation of 3-5 and 3-6 has been confirmed by the fact that treatment of weakeracidic 3-1e with excess of carbodiimides in THF/toluene, even with prolonged heating,provides only the mono-addition productCp2Yb[η21-CyNC(NHCy)NC6H4(CH2NH2-2)] [R=Cy (3-8a), iPr (3-8b)]. Werealizes the nature of the functional group at amido ligands often exerts a significantinfluence on the outcome of the reaction, and provides a detailed insight into generalmechanistic aspects of the metal-mediated mono- and di-guanylation of primaryamines and the flexibility and distinct reactivity of the linked diguanidinate ligand.Chapter four describes selective reaction based on the linked diamido ligands ofdinuclear lanthanide complexes. The dinuclear pyridyl diamido ytterbium complexes[Cp2Yb(THF)]2 [μ-η12-(NH)2(C5H3N-2,6)] (4-1a) and[Cp2Yb(THF)]2[μ-η12-(NH)2(C5H3N-2,3)] (4-1b) are easily prepared byprotonolysis of Cp3Yb with 0.5 equiv of the corresponding diaminopyridine inaccepted yields, respectively. Treatment of 4-1a with 2 equiv of carbodiimides(RN=C=NR, R=Cy, iPr) in THF at low temperature leads to the isolation of theformal double N-H addition product (Cp2Yb)2[μ-η22-{RN(RNH)CN}2(C5H3N-2,6)] (4-2a R=Cy, 4-2b R=iPr). Compound 4-2 is unstable to heat and slowly isomerizesto the mixed neutral/dianionic diguanidinate complex(Cp2Yb)2[μ-η22-(RNH)2CN(C5H3N-2, 6)NC(NR)2](THF) (4-3a R=Cy, 4-3b R=iPr)at room temperature, while complex 4-3b can be further transformed into the complex4-4 with elimination of cyclopentadiene at 70℃. In addition, an unexpected oxidecomplex [(CpYb)2{μ-η222-2,6-(iPrN(iPrNH)C=N)2C5H3N}(μ3-O)]2 (4-5) wasisolated as red crystals when 4-2b was recrystallized in THF. Similarly, treatment of4-1b with two equiv of CyN=C=NCy gives the addition/isomerization product(Cp2Yb)2[μ-η221-(CyNH)2CN(C5H3N-2,3)NC(NCy)2] (4-6). Moreover, thereaction of various aryl diamido ytterbium complexes (prepared in situ from[Cp2YbMe]2 and aryldiamine, respectively) with CyN-C=NCy affords thecorresponding addition products (Cp2Yb)2[μ-η22-{CyN(CyNH)C-N}2(-C6H4-1,4)](4-7), (Cp2Yb)2[μ-η22-{CyN(CyNH)CN}2(C6H4-1,3)] (4-8), and(Cp2Yb)2[μ-η22-{CyN(CyNH)CN}2(C13H8-2,7)] (4-9), respectively. In contrast topyridyl-bridged di(guanidinate monoanion) complexes, aryl-bridged di(guanidinatemonoanion) complexes 4-7-9 are stable even with prolonged heating at 110℃. Allthe results not only demonstrate that the presence of the pyridyl bridge can impart thediamido complexes a unique reactivity and initiates the unexpected reaction sequence.Chapter five explores the reaction of carbondiimide with Cp3Ln (Cp=C5H5, andCp3*Ln (Cp*=C5H4Me) to form lanthanide-substituted aminate by Cp and Cp*activation in a selective insertion reaction under appropriate reaction conditions. Thereaction activity was found to be highly dependent on the solvent, the temperature, themental ionic radius and the nucleophilic of the Cp. In this study, we have alsosuccessfully isolated and well charactered (RN=C=NR)LnCp3 and(RN=C=NR)YCp3* which are the proposed intermediate in the mechanism of initialcoordination/following transfer/insertion, and lanthanide-substituted aminateCp2Ln(RNC(Cp)NR) (Ln=Y, Yb, Er) and Cp2*Ln(RNC(Cp*)NR) (Ln=Y, Yb). Theresults presented in this work greatly extend the synthetic schemes available towardslanthanide complexes and further the understanding of relations between structuralpreferences and natures of ligand.

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