A New Family of Zirconium Complexes Anchored by Dianionic Cyclam‐Based Ligands: Syntheses, Structures, and Catalytic Applications

Martins, Ana M.; Munhá, Rui F.; Alves, Luís G.; Bharathi, S.

doi:10.1002/9781118742952.ch25

Cited by 2 publications

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“…The Y(1)-O(1) and Y(1)-C(24) distances of 2.492(3) and 2.479(5) Å, respectively, are within the usual ranges [66,71-73]. The lithium cation displays typical tetrahedral coordination with regular Li-N and Li-O distances[44,74,75].It was previously reported that 3,5-disubstitution of the benzyl pending arms of cyclam by bulky groups made C-H activation reactions difficult to occur[76]. This feature might allow the stabilization of yttrium alkyl complexes having dianionic cyclams as anchoring ligands.…”

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confidence: 75%

“…The driving force for the reaction may be the strong ionic character of Y(III) and its tendency to form charge-separated species, either zwitterions or ions pairs, often observed for amido yttrium complexes in polar solvents [63,64]. It was previously reported that 3,5-disubstitution of the benzyl pending arms of cyclam by bulky groups made C-H activation reactions difficult to occur [76]. This feature might allow the stabilization of yttrium alkyl complexes having dianionic cyclams as anchoring ligands.…”

Section: Resultsmentioning

confidence: 99%

“…Thus, the reaction of H2( 3,5-tBu2 Bn)2Cyclam, 5, with Y(CH2SiMe3)3(THF)2, prepared in situ from YCl3 and LiCH2SiMe3 in a 1:3 ratio, in THF at −20 °C was attempted. The resulting compound was the yttrium ate complex [Y{(η 3 -3,5-tBu2 Bn)2Cyclam}Li(THF)], It was previously reported that 3,5-disubstitution of the benzyl pending arms of cyclam by bulky groups made C-H activation reactions difficult to occur [76]. This feature might allow the stabilization of yttrium alkyl complexes having dianionic cyclams as anchoring ligands.…”

Section: Resultsmentioning

confidence: 99%

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Synthesis, Characterization, and Reactivity Studies of New Cyclam-Based Y(III) Complexes

Madeira,

Veiros,

Alves

et al. 2023

Molecules

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[(Bn2Cyclam)Y(N(SiMe3)2)] was prepared by reaction of H2Bn2Cyclam with Y[N(SiMe3)2]3. The protonation of the macrocycle ligand in [(Bn2Cyclam)Y(N(SiMe3)2)] is observed upon reaction with [HNMe3][BPh4] leading to the formation of [(HBn2Cyclam)Y(N(SiMe3)2)][BPh4]. DFT analysis of [(Bn2Cyclam)Y(N(SiMe3)2)] showed that the HOMO is located on the anionic nitrogen atoms of the cyclam ring indicating that protonation follows orbital control. Addition of H2Bn2Cyclam and H2(3,5-tBu2Bn)2Cyclam to a 1:3 mixture of YCl3 and LiCH2SiMe3 in THF resulted in the formation of [((C6H4CH2)BnCyclam)Y(THF)(µ-Cl)Li(THF)2] and [Y{(η3-3,5-tBu2Bn)2Cyclam}Li(THF)], respectively. The reaction of H23,5-tBu2Bn2Cyclam with Y(CH2SiMe3)3(THF)2 was studied and monitored by a temperature variation NMR experiment revealing the formation of [(3,5-tBu2Bn2Cyclam)Y(CH2SiMe3)]. Preliminary catalytic assays have shown that [Y{(η3-3,5-tBu2Bn)2Cyclam}Li(THF)] is a very efficient catalyst for the intramolecular hydroamination of 2,2-diphenyl-pent-4-enylamine.

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confidence: 75%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Synthesis, Characterization, and Reactivity Studies of New Cyclam-Based Y(III) Complexes

Madeira,

Veiros,

Alves

et al. 2023

Molecules

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Cooperative Metal–Ligand Hydroamination Catalysis Supported by C–H Activation in Cyclam Zr(IV) Complexes

et al. 2018

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Complexes of the type (R2Cyclam)ZrCl2 (where R = CH2C(H)CH2 (All), CH2C(Me)CH2 (MeAll), and PhCH2 (Bn)) react with suitable Grignard reagents to produce the corresponding alkyl derivatives (R2Cyclam)ZrR′2 (R′ = Me, CH2Ph). Thermally induced double metalation of the pending arms of the cyclam ligand led to the formation of complexes ((CHC(H)CH2)2Cyclam)Zr, 14, ((CHC(Me)CH2)2Cyclam)Zr, 15, or ((C6H4CH2)2Cyclam)Zr, 16. These reactions proceed through C(sp2)–H bond activation and R′H elimination and convert the original dianionic tetracoordinated cyclam-based ligands in tetraanionic hexacoordinated ligands that establish two new Zr–C bonds. The cleavage of the Zr–C bonds may be readily achieved by treatment of the bis(ortho-metalated) species 16 with protic substrates (tert-butanol, phenol, thiophenol, aniline, benzophenone hydrazone, pyrazole, and N,N′-diphenylhydrazine), to give rise to (Bn2Cyclam)ZrX2 complexes (X = OtBu, OPh, SPh, NHPh, NHNCPh2, C3H3N2, N,N′-PhNNPh). In catalytic conditions, complexes (All2Cyclam)Zr(NMe2)2, 14, 15, or 16 convert 2,2-diphenyl-pent-4-enylamine to 2-methyl-4,4-diphenylpyrrolidine with 100% selectivity and conversion values varying between 61 and 88% in 4.5 h, at 115 °C. Complexes 14 and 15, which display metalated allyl and methallyl pending groups on the cyclam ring, are the most active species (1.7 < TOF < 2.0 h–1). The mechanism of this reaction was studied by density functional theory that revealed two competitive paths, one proceeding through an imido intermediate and another that occurs via an amido ligand. Both cases represent cooperative mechanisms with active participation of the cyclam, as proton exchange between the coordinated substrate and the ligand side arm with reversible C–H activation is a crucial feature of the mechanism.

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A New Family of Zirconium Complexes Anchored by Dianionic Cyclam‐Based Ligands: Syntheses, Structures, and Catalytic Applications

Cited by 2 publications

References 87 publications

Synthesis, Characterization, and Reactivity Studies of New Cyclam-Based Y(III) Complexes

Synthesis, Characterization, and Reactivity Studies of New Cyclam-Based Y(III) Complexes

Cooperative Metal–Ligand Hydroamination Catalysis Supported by C–H Activation in Cyclam Zr(IV) Complexes

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