Tris(pyrazolyl)methanide Complexes of Trivalent Rare-Earth Metals

Three types of trivalent rare-earth-metal complexes supported by a monoanionic tris­(pyrazolyl)­methanide ligand were synthesized and structurally characterized, and the catalytic activity of the dialkyl derivatives for isoprene polymerization was investigated. Reactions of the lithium salt of tris­(3,5-dimethylpyrazolyl)­methanide <b>L</b>Li­(THF) with 1 equiv of ScCl₃(THF)₃, YCl₃, or LuCl₃ in THF provided the ion-pair complexes [<b>L</b>LnCl₃]­[Li­(THF)₄] (Ln = Sc (<b>1</b>), Y (<b>2</b>), Lu (<b>3</b>)). Dialkyl complexes <b>L</b>Ln­(CH₂SiMe₃)₂(THF) (Ln = Y (<b>4</b>), Lu (<b>5</b>)) were prepared by salt metathesis of <b>L</b>Li­(THF) with 1 equiv of [Y­(CH₂SiMe₃)₂(THF)₃]­[BPh₄] or [Lu­(CH₂SiMe₃)₂(THF)₃]­[BPh₄] in toluene. Reaction of <b>5</b> with PhSiH₃ provided the unexpected alkylidene-bridged dinuclear complex <b>L</b>₂Lu₂(μ-η¹:η¹-3,5-(CH₃)­C₃HN₂)₂(μ-CHSiMe₃) (<b>6</b>). Complexes <b>1</b>–<b>6</b> were structurally characterized by single-crystal X-ray diffraction, showing that the tris­(pyrazolyl)­methanide ligand acts as a κ³-coordinating six-electron donor in all complexes. The dialkyl complexes catalyzed 1,4-cis polymerization of isoprene with high selectivity upon activation with borate and alkylaluminum

CNC-Pincer Rare-Earth Metal Amido Complexes with a Diarylamido Linked Biscarbene Ligand: Synthesis, Characterization, and Catalytic Activity

In preparation of CNC-pincer rare-earth metal amido complexes with a diarylamido linked biscarbene ligand, it is found that conditions have a key influence on final products. Reaction of a THF suspension of bis­[2-(3-benzyl­imidazolium)-4-methyl­phenyl]­amine dichlorides (H₃<b>L</b>Cl₂) with [(Me₃Si)₂­N]₃­RE­(μ-Cl)­Li­(THF)₃ (RE = Yb, Eu, Sm) in THF at room temperature afforded the only unexpected fused-heterocyclic compound 8,9-dibenzyl-3,14-dimethyl-8<i>a</i>,9-dihydro-8<i>H</i>-benzo­[4,5]­imidazo­[2′,1′:2,3]­imidazo­[1,2-<i>a</i>]­imidazo­[2,1-<i>c</i>]­quinoxaline (<b>1</b>) containing an imidazolyl ring and a piperidyl ring, which formed through carbene C–C and C–N coupling. However, the reaction of H₃<b>L</b>Cl₂ with [(Me₃Si)₂­N]₃­Er­(μ-Cl)­Li­(THF)₃ in toluene afforded the CNC-pincer erbium amido complex incorporating a diarylamido linked biscarbene ligand <b>L</b>Er­[N­(SiMe₃)₂]₂ (<b>2</b>) in low yield and the above fused-heterocyclic compound <b>1</b>. The stepwise reaction of H₃<b>L</b>Cl₂ with strong bases (<i>n</i>-BuLi or LiCH₂SiMe₃) in THF for 4 h, followed by treatment with [(Me₃Si)₂­N]₃­RE­(μ-Cl)­Li­(THF)₃, generated zwitterion complexes [<b>L</b>₂RE]­[RECl­{N­(SiMe₃)₂}₃] (<b>L</b> = [4-CH₃-2-{(C₆H₄CH₂-[N­(CH)₂­CN]}­C₆H₃]₂N; RE = Y (<b>3</b>), Er (<b>4</b>), Yb (<b>5</b>)) in less than 20% yields together with fused-heterocyclic compound <b>1</b>. Additionally, the reaction of H₃<b>L</b>Cl₂ with 6 equiv of NaN­(SiMe₃)₂ in THF for 4 h, followed by treatment with YbCl₃, generated a novel discrete complex [<b>L</b>₂Yb]­[{Na­(μ-N­(SiMe₃)₂)}₅­(μ₅-Cl)] (<b>6</b>). The one-pot reaction of H₃<b>L</b>Cl₂ with <i>n</i>-BuLi, followed by reaction with [(Me₃Si)₂­N]₃­RE­(μ-Cl)­Li­(THF)₃ in THF at −78 °C, generated the CNC-pincer lanthanide bisamido complexes <b>L</b>RE­[N­(SiMe₃)₂]₂ (RE = Er (<b>2</b>), Y (<b>7</b>), Sm (<b>8</b>), Eu (<b>9</b>)) in moderate yields. These kinds of biscarbene supported pincer bisamido complexes could also be prepared by a one-pot reaction of bis­(imidazolium) salt (H₃<b>L</b>Cl₂) with 5 equiv of NaN­(SiMe₃)₂, followed by treatment with RECl₃, in good yields at −78 °C. Investigation of the catalytic activity of complexes <b>2</b> and <b>7</b>–<b>9</b> indicated that all complexes showed a high activity toward the addition of terminal alkynes to carbodiimides producing propiolimidines, which represents the first example of rare-earth metal CNC-pincer-type catalysts applied for catalytic C–H bond addition of terminal alkynes to carbodiimides at room temperature

Synthesis and Characterization of Rare-Earth Metal Complexes Supported by 2‑Imino or Amino Appended Indolyl Ligands with Diverse Hapticities: Tunable Selective Catalysis for Isoprene Polymerization

The reaction of 2-(2,6-DippNHCH₂)­C₈H₅NH (Dipp = 2,6-^<i>i</i>PrC₆H₃, C₈H₅NH = indolyl) with 1 equiv of (Me₃SiCH₂)₃Yb­(THF)₂ at room temperature generated mononuclear ytterbium complex <b>1</b> having the indolyl ligands in η¹:η¹ mode with reduction of Yb³⁺ to Yb²⁺ and oxidation of the amino to imino group. In the case of Er and Y, the reactions produced dinuclear complexes <b>2</b> and <b>3</b> having the indolyl ligands in μ-η²:η²:η¹ modes with the central metals. When the rare-earth metal is dysprosium, the reaction afforded mixed ligated dinuclear complex <b>4a</b> having indolyl ligands in μ-η⁵:η¹:η¹ and μ-η⁶:η¹:η¹ modes with Dy, and its isomer <b>4b</b> having the indolyl ligands only in μ-η⁵:η¹:η¹ modes with Dy. However, when the rare-earth metal is Gd, the reaction only produced the mixed ligated dinuclear gadolinium complex [(μ-η⁵:η¹:η¹)-2-(2,6-DippNCH₂)­Ind­(μ-η⁶:η¹:η¹)-2-(2,6-DippNCH₂)­Ind]­[Gd­(CH₂SiMe₃)­(thf)]₂ (<b>5</b>), having indolyl ligands in μ-η⁵:η¹:η¹ and μ-η⁶:η¹:η¹ modes with Gd. In addition, treatment of 2-(2,6-DippNHCH₂)­C₈H₅NH with 1.25 equiv of (Me₃SiCH₂)₃Gd­(THF)₂ produced the alkoxido-bridged trinuclear gadolinium complex [(μ-η³:η²:η¹:η¹)-2-(2,6-DippNCH₂)­Ind­(μ-η²:η¹:η¹)-2-(2,6-DippNCH₂)­Ind<i>-</i>(η¹:η¹)-2-(2,6-DippNCH₂)­Ind]-Gd₃[(μ₃<i>-</i>O­(CH₂)₅SiMe₃)­(μ₂-O­(CH₂)₅SiMe₃)­(thf)₃] (<b>6</b>) having indolyl ligands in η¹:η¹, μ-η²:η¹:η¹, and μ-η³:η²:η¹:η ¹ modes with metals, respectively. In complex <b>6</b>, sp² C–H activation is observed at the 7-indolyl position producing unique 2-amido substituted indolyl-1,7-dianions having a μ-η³:η²:η¹:η¹ bonding modes with three metals. The O­(CH₂)₅SiMe₃ arises from the ring-opening of THF by attack of CH₂SiMe₃. Moreover, when 2-(2,6-DippNHCH₂)­C₈H₅NH was treated with 1 equiv of (Me₃SiCH₂)₃Sm­(THF)₂, a dinuclear samarium complex [μ-η³:η¹:η¹-2-(2,6-DippNCH₂)­Ind]₃Sm₂(thf)₃ (<b>7</b>) having a bridged indolyl ligand in μ-η³:η¹:η¹ hapticities was isolated. All structures of the complexes have been determined by X-ray crystallographic analyses. Dinuclear alkyl complexes <b>2</b>–<b>5</b> have been tested as isoprene polymerization initiators in the presence of Al^<i>i</i>Bu₃ and [Ph₃C]­[B­(C₆F₅)₄]. The regioselectivity for isoprene polymerization is tunable from 1,4-<i>cis</i> (up to 93.5%) to 3,4- (up to 86.2%) selectivity by these catalysts simply by adjusting the addition order of Al^<i>i</i>Bu₃ and [Ph₃C]­[B­(C₆F₅)₄]

Synthesis and Reactivity of Rare-Earth-Metal Monoalkyl Complexes Supported by Bidentate Indolyl Ligands and Their High Performance in Isoprene 1,4-cis Polymerization

A series of novel rare-earth-metal monoalkyl complexes incorporating partially rotation restricted [N,N]-bidentate indolyl ligands were synthesized and characterized, and their reactivities and catalytic activities were investigated. Treatment of [RE­(CH₂SiMe₃)₃(thf)₂] with 1 equiv of 2-[(<i>N</i>-2,6-diisopropylphenyl)­iminomethyl)]­indole (2-(2,6-^<i>i</i>Pr₂C₆H₃NCH)­C₈H₅NH) in toluene at room temperature afforded the rare-earth-metal monoalkyl complexes [η¹:η¹-2-(2,6-^<i>i</i>Pr₂C₆H₃NCH)­Ind]₂RE­(CH₂SiMe₃)­(thf) (Ind = indolyl; RE = Yb (<b>1</b>), Er (<b>2</b>), Y (<b>3</b>), Dy (<b>4</b>), Gd (<b>5</b>)) and the samarium complex [η¹:η¹-2-(2,6-^<i>i</i>Pr₂C₆H₃NCH)­Ind]₃Sm (<b>6</b>) via alkane elimination in good yields. Treatment of complex <b>2</b> or <b>3</b> with 1 equiv of PhSiH₃ in toluene at 80 °C for 12 h afforded the dinuclear complexes {[μ-η⁶:η¹:η¹-2-(2,6-^<i>i</i>Pr₂C₆H₃NCH₂)­Ind]­RE­[2-(2,6-^<i>i</i>Pr₂C₆H₃NCH)­Ind]}₂ (Ind = indolyl, RE = Er (<b>7</b>), Y (<b>8</b>)) in good isolated yields. Treatment of complex <b>2</b> or <b>3</b> with 1 equiv of amidine (2,6-^<i>i</i>Pr₂C₆H₃)­NCHNH­(2,6-^<i>i</i>Pr₂C₆H₃) in toluene produced the corresponding complexes [η¹:η¹-2-(2,6-^<i>i</i>Pr₂C₆H₃NCH)­C₈H₅N]₂RE­[(2,6-^<i>i</i>Pr₂C₆H₃)­NCHN­(2,6-^<i>i</i>Pr₂C₆H₃)] (RE = Er (<b>9</b>), Y (<b>10</b>)) possessing the amidinate ligand [(2,6-^<i>i</i>Pr₂C₆H₃N)₂CH]⁻. The molecular structures of all complexes were determined by X-ray crystallography. The monoalkyl complexes <b>1</b>–<b>5</b> were tested as isoprene polymerization initiators. Among the complexes investigated, the optimum combination <b>5</b>/Al^<i>i</i>Bu₃/[Ph₃C]­[B­(C₆F₅)₄] displayed a high catalytic activity in isoprene polymerization, producing polymers with an extremely high 1,4-cis selectivity (up to 99%), a high number-average molecular weight (<i>M</i>_n = 7.2 × 10⁵), and a narrow molecular weight distribution (PDI = 1.34) at an isoprene to initiator molar ratio of 6000:1

Synthesis and Reactivity of Rare-Earth-Metal Monoalkyl Complexes Supported by Bidentate Indolyl Ligands and Their High Performance in Isoprene 1,4-cis Polymerization

A series of novel rare-earth-metal monoalkyl complexes incorporating partially rotation restricted [N,N]-bidentate indolyl ligands were synthesized and characterized, and their reactivities and catalytic activities were investigated. Treatment of [RE­(CH₂SiMe₃)₃(thf)₂] with 1 equiv of 2-[(<i>N</i>-2,6-diisopropylphenyl)­iminomethyl)]­indole (2-(2,6-^<i>i</i>Pr₂C₆H₃NCH)­C₈H₅NH) in toluene at room temperature afforded the rare-earth-metal monoalkyl complexes [η¹:η¹-2-(2,6-^<i>i</i>Pr₂C₆H₃NCH)­Ind]₂RE­(CH₂SiMe₃)­(thf) (Ind = indolyl; RE = Yb (<b>1</b>), Er (<b>2</b>), Y (<b>3</b>), Dy (<b>4</b>), Gd (<b>5</b>)) and the samarium complex [η¹:η¹-2-(2,6-^<i>i</i>Pr₂C₆H₃NCH)­Ind]₃Sm (<b>6</b>) via alkane elimination in good yields. Treatment of complex <b>2</b> or <b>3</b> with 1 equiv of PhSiH₃ in toluene at 80 °C for 12 h afforded the dinuclear complexes {[μ-η⁶:η¹:η¹-2-(2,6-^<i>i</i>Pr₂C₆H₃NCH₂)­Ind]­RE­[2-(2,6-^<i>i</i>Pr₂C₆H₃NCH)­Ind]}₂ (Ind = indolyl, RE = Er (<b>7</b>), Y (<b>8</b>)) in good isolated yields. Treatment of complex <b>2</b> or <b>3</b> with 1 equiv of amidine (2,6-^<i>i</i>Pr₂C₆H₃)­NCHNH­(2,6-^<i>i</i>Pr₂C₆H₃) in toluene produced the corresponding complexes [η¹:η¹-2-(2,6-^<i>i</i>Pr₂C₆H₃NCH)­C₈H₅N]₂RE­[(2,6-^<i>i</i>Pr₂C₆H₃)­NCHN­(2,6-^<i>i</i>Pr₂C₆H₃)] (RE = Er (<b>9</b>), Y (<b>10</b>)) possessing the amidinate ligand [(2,6-^<i>i</i>Pr₂C₆H₃N)₂CH]⁻. The molecular structures of all complexes were determined by X-ray crystallography. The monoalkyl complexes <b>1</b>–<b>5</b> were tested as isoprene polymerization initiators. Among the complexes investigated, the optimum combination <b>5</b>/Al^<i>i</i>Bu₃/[Ph₃C]­[B­(C₆F₅)₄] displayed a high catalytic activity in isoprene polymerization, producing polymers with an extremely high 1,4-cis selectivity (up to 99%), a high number-average molecular weight (<i>M</i>_n = 7.2 × 10⁵), and a narrow molecular weight distribution (PDI = 1.34) at an isoprene to initiator molar ratio of 6000:1

Synthesis, Structure, and Reactivity of Lanthanide Complexes Incorporating Indolyl Ligands in Novel Hapticities

The chemistry of interactions of 2-(2,6-diisopropylphenylaminomethylene)­indole ligand (<b>1</b>) with europium and ytterbium amides is described. Reaction of 2-(2,6-diisopropylphenylaminomethylene)­indole 2-(2,6-<i>i</i>-Pr₂C₆H₃NHCH₂)­C₈H₅NH (<b>1</b>) with europium amide [(Me₃Si)₂N]₃Eu^III(μ-Cl)­Li­(THF)₃ afforded a novel europium­(II) complex formulated as {[μ-η⁶:η¹:η¹-2-(2,6-<i>i</i>-Pr₂C₆H₃NCH)­C₈H₅N]­Eu­[2-(2,6-<i>i</i>-Pr₂C₆H₃NCH)­C₈H₅N]}₂ (<b>2</b>), having a bridged indolyl ligand in the novel μ-η⁶:η¹:η¹ hapticities with the reduction of europium­(III) to europium­(II) and the oxidation of amino to imino group. Reaction of 2-(2,6-diisopropylphenylaminomethylene)­indole 2-(2,6-<i>i</i>-Pr₂C₆H₃NHCH₂)­C₈H₅NH (<b>1</b>) with ytterbium­(III) amide [(Me₃Si)₂N]₃Yb^III(μ-Cl)­Li­(THF)₃ produced the only deprotonated ytterbium­(III) complex formulated as [2-(2,6-<i>i</i>-Pr₂C₆H₃NCH₂)­C₈H₅N]­Yb­[N­(SiMe₃)₂]­(THF)₂ (<b>3</b>), having an η¹ hapticity indolyl ligand. Reaction of <b>2</b> with formamidine [(2,6-Me₂C₆H₃)­NCHNH­(C₆H₃Me₂-2,6)] produced {[μ-η³:η¹:η¹-2-(2,6-<i>i</i>-Pr₂C₆H₃NCH)­C₈H₅N]­Eu­[(2,6-Me₂C₆H₃)­NCHN­(C₆H₃Me₂-2,6)]­(THF)}₂ (<b>4</b>), which has a bridged indolyl ligand in the novel μ-η³:η¹:η¹ hapticities, whereas the reaction of <b>2</b> with the more sterically bulky formamidine [(2,6-<i>i</i>-Pr₂C₆H₃)­NCHNH­(C₆H₃<i>i</i>-Pr₂-2,6)] afforded complex {[μ-η²:η¹:η¹-2-(2,6-<i>i</i>-Pr₂C₆H₃NCH)­C₈H₅N]­Eu­[(2,6-<i>i</i>-Pr₂C₆H₃)­NCHN­(C₆H₃<i>i</i>-Pr₂-2,6)]­(THF)}₂ (<b>5</b>), having the indolyl ligand in the novel μ-η²:η¹:η¹ hapticities. The results represent the first example of organometallic complexes having indolyl ligands in the novel μ-η⁶:η¹:η¹, μ-η³:η¹:η¹, and μ-η²:η¹:η¹ bonding modes with metal

Synthesis, Structure, and Reactivity of Lanthanide Complexes Incorporating Indolyl Ligands in Novel Hapticities

The chemistry of interactions of 2-(2,6-diisopropylphenylaminomethylene)­indole ligand (<b>1</b>) with europium and ytterbium amides is described. Reaction of 2-(2,6-diisopropylphenylaminomethylene)­indole 2-(2,6-<i>i</i>-Pr₂C₆H₃NHCH₂)­C₈H₅NH (<b>1</b>) with europium amide [(Me₃Si)₂N]₃Eu^III(μ-Cl)­Li­(THF)₃ afforded a novel europium­(II) complex formulated as {[μ-η⁶:η¹:η¹-2-(2,6-<i>i</i>-Pr₂C₆H₃NCH)­C₈H₅N]­Eu­[2-(2,6-<i>i</i>-Pr₂C₆H₃NCH)­C₈H₅N]}₂ (<b>2</b>), having a bridged indolyl ligand in the novel μ-η⁶:η¹:η¹ hapticities with the reduction of europium­(III) to europium­(II) and the oxidation of amino to imino group. Reaction of 2-(2,6-diisopropylphenylaminomethylene)­indole 2-(2,6-<i>i</i>-Pr₂C₆H₃NHCH₂)­C₈H₅NH (<b>1</b>) with ytterbium­(III) amide [(Me₃Si)₂N]₃Yb^III(μ-Cl)­Li­(THF)₃ produced the only deprotonated ytterbium­(III) complex formulated as [2-(2,6-<i>i</i>-Pr₂C₆H₃NCH₂)­C₈H₅N]­Yb­[N­(SiMe₃)₂]­(THF)₂ (<b>3</b>), having an η¹ hapticity indolyl ligand. Reaction of <b>2</b> with formamidine [(2,6-Me₂C₆H₃)­NCHNH­(C₆H₃Me₂-2,6)] produced {[μ-η³:η¹:η¹-2-(2,6-<i>i</i>-Pr₂C₆H₃NCH)­C₈H₅N]­Eu­[(2,6-Me₂C₆H₃)­NCHN­(C₆H₃Me₂-2,6)]­(THF)}₂ (<b>4</b>), which has a bridged indolyl ligand in the novel μ-η³:η¹:η¹ hapticities, whereas the reaction of <b>2</b> with the more sterically bulky formamidine [(2,6-<i>i</i>-Pr₂C₆H₃)­NCHNH­(C₆H₃<i>i</i>-Pr₂-2,6)] afforded complex {[μ-η²:η¹:η¹-2-(2,6-<i>i</i>-Pr₂C₆H₃NCH)­C₈H₅N]­Eu­[(2,6-<i>i</i>-Pr₂C₆H₃)­NCHN­(C₆H₃<i>i</i>-Pr₂-2,6)]­(THF)}₂ (<b>5</b>), having the indolyl ligand in the novel μ-η²:η¹:η¹ hapticities. The results represent the first example of organometallic complexes having indolyl ligands in the novel μ-η⁶:η¹:η¹, μ-η³:η¹:η¹, and μ-η²:η¹:η¹ bonding modes with metal

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 (<b>1</b>) in toluene afforded the corresponding lanthanide amides with the formula [η⁵:η¹-(2,5-Me₂C₄H₂N)­CH₂CH₂]₂­NLn­[N­(SiMe₃)₂]₂ (Ln = La (<b>2</b>), Nd (<b>3</b>)). Reaction of <b>2</b> or <b>3</b> with <i>N</i>,<i>N</i>′-dicyclo­hexyl­carbo­diimide (CyNCNCy) gave the carbodiimide selectively inserted into the appended Ln–N bond products formulated as CyNC­{[<i>N</i>,<i>N</i>-(2,5-Me₂C₄H₂N)­CH₂CH₂]₂N}­NCyLn­[N­(SiMe₃)₂]₂ (Ln = La (<b>4</b>), Nd (<b>5</b>)). 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 (<b>1</b>), 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 (<b>6</b>). The stoichiometric reactions of lanthanide amides <b>2</b> or <b>3</b> 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 (<b>7</b>), Nd (<b>8</b>)) 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 <b>2</b>, or <b>3</b> with Me₃SiCN, complexes <b>2</b>, <b>3</b>, <b>4</b>, <b>5</b>, <b>7</b>, and <b>8</b> 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 <b>7</b> ∼ <b>8</b> > <b>2</b> ∼ <b>3</b> ∼ <b>4 ∼ <b>5</b></b>. Thus, complex <b>7</b> or <b>8</b> was proposed as the active catalyst in the catalytic reaction for the precatalysts of <b>2</b> and <b>3</b>

Synthesis of Bis(NHC)-Based CNC-Pincer Rare-Earth-Metal Amido Complexes and Their Application for the Hydrophosphination of Heterocumulenes

The bis­(NHC) (NHC = N-heterocyclic carbene)-based CNC-pincer rare-earth-metal amido complexes <b>L</b>RE­[N­(SiMe₃)₂]₂ (<b>L</b> = 4-CH₃-2-{R-[N­(CH)₂CN]}­C₆H₃]₂N; <b>L</b>^<b>2</b>, R = CH₃; <b>L</b>^<b>3</b>, R = CH­(CH₃)₂) were synthesized and characterized, and their catalytic activities toward hydrophosphination of heterocumulenes were developed. Reactions of bis­[2-(3-methylimidazolium)-4-methylphenyl]­amine diiodide (H₃<b>L</b>^<b>2</b>I₂) or bis­[2-(3-isopropylimidazolium)-4-methylphenyl]­amine diiodide (H₃<b>L</b>^<b>3</b>I₂) with 5 equiv of NaN­(SiMe₃)₂ followed by treatment with 1 equiv of RECl₃ in THF at −78 °C afforded the bis­(NHC)-based CNC-pincer rare-earth-metal amido complexes <b>L</b>RE­[N­(SiMe₃)₂]₂ (<b>L</b>^<b>2</b> = [4-CH₃-2-{CH₃-[N­(CH)₂CN]}­C₆H₃]₂N, RE = Y (<b>1</b>), Eu (<b>2</b>), Er (<b>3</b>); <b>L</b>^<b>3</b> = [4-CH₃-2-{(CH₃)₂CH-[N­(CH)₂CN]}­C₆H₃]₂N, RE = Y (<b>4</b>), Er (<b>5</b>), Yb (<b>6</b>)). Complexes <b>4</b>–<b>6</b> can also be prepared by stepwise reactions of H₃<b>L</b>^<b>3</b>I₂ with <i>n</i>-BuLi in THF followed by reactions with [(Me₃Si)₂N]₃RE­(μ-Cl)­Li­(THF)₃. Stepwise reactions of H₃<b>L</b>^<b>2</b>I₂ with <i>n</i>-BuLi in THF followed by treatment with [(Me₃Si)₂N]₃RE­(μ-Cl)­Li­(THF)₃ generated the bis­(NHC)-based CNC-pincer rare-earth-metal amido complexes <b>L</b>^<b>2</b>RE­[N­(SiMe₃)₂]₂ (RE = Y (<b>1</b>), Er (<b>3</b>)) together with the fused-heterocyclic compound 3,8,9-trimethyl-8a,9-dihydro-8<i>H</i>-benzo­[4,5]­imidazo­[2′,1′:2,3]­imidazo­[1,2-<i>a</i>]­imidazo­[2,1-<i>c</i>]­quinoxaline (<b>7</b>), which formed through carbene C–C and C–N coupling. Attempts to prepare complexes of the type <b>L</b>RE­[N­(SiMe₃)₂]₂ by reaction of H₃<b>L</b>^<b>3</b>I₂ with [(Me₃Si)₂N]₃Yb­(μ-Cl)­Li­(THF)₃ in THF, however, afforded mixed complexes of the bis­(NHC)-based CNC-pincer ytterbium complex <b>L</b>^<b>3</b>Yb­[N­(SiMe₃)₂]₂ (<b>6</b>) and the unexpected bis­(NHC)-based CNC-pincer monoamido ytterbium iodide <b>L</b>^<b>3</b>YbI­[N­(SiMe₃)₂] (<b>8</b>). Investigation of the catalytic activity of complexes <b>1</b>–<b>6</b> and <b>8</b> indicated that all complexes displayed high activity toward the addition of the phosphine P–H bond to heterocumulenes, producing the corresponding phosphaguanidines, phosphaureas, and phosphathioureas, which represents the first example of bis­(NHC)-based CNC-pincer type rare-earth-metal amido complexes as catalysts for the catalytic addition of the phosphine P–H bond to heterocumulenes with high efficiency in the presence of a low catalyst loading at room temperature

Synthesis and Characterization of Organo-Rare-Earth Metal Monoalkyl Complexes Supported by Carbon σ‑Bonded Indolyl Ligands: High Specific Isoprene 1,4-Cis Polymerization Catalysts

A series of <i>N</i>-protected 3-imino-functionalized indolyl ligands 1-R-3-(R′NCH)­C₈H₅N [R = Bn, R′ = 2,6-^<i>i</i>Pr₂C₆H₃ (<b>HL</b>^<b>1</b>); R = CH₃, R′ = 2,6-^<i>i</i>Pr₂C₆H₃ (<b>HL</b>^<b>2</b>); R = Bn, R′ = ^<i>t</i>Bu (<b>HL</b>^<b>3</b>)] and 1-CH₃-2-(2,6-^<i>i</i>Pr₂C₆H₃NCH)­C₈H₅N (<b>HL</b>^<b>4</b>) was prepared via reactions of <i>N</i>-protected indolyl aldehydes with corresponding amines. The C–H σ-bond metathesis followed by alkane elimination reactions between RE­(CH₂SiMe₃)₃(thf)₂ and <b>HL</b>^<b>1</b><b>–HL</b>^<b>3</b> afforded the carbon σ-bonded indolyl-ligated rare-earth metal monoalkyl complexes. Reactions of RE­(CH₂SiMe₃)₃(thf)₂ with 2 equiv of <b>HL</b>^<b>1</b> or <b>HL</b>^<b>2</b> gave the carbon σ-bonded indolyl-ligated rare-earth metal monoalkyl complexes <b>L</b>^<b>1</b>₂RECH₂SiMe₃ (RE = Y­(<b>1</b>), Er­(<b>2</b>), Dy­(<b>3</b>)) and <b>L</b>^<b>2</b>₂RECH₂SiMe₃ (RE = Y­(<b>5</b>), Er(6), Dy­(<b>7</b>), Yb­(<b>8</b>)), while reaction of Yb­(CH₂SiMe₃)₃(thf)₂ with 2 equiv of <b>HL</b>^<b>1</b> afforded the ytterbium dialkyl complex <b>L</b>^<b>1</b>Yb­(CH₂SiMe₃)₂(thf)₂ (<b>4</b>). Reactions of RE­(CH₂SiMe₃)₃(thf)₂ with <b>HL</b>^<b>3</b> gave the tris­(heteroaryl) rare-earth metal complexes <b>L</b>^<b>3</b>₃RE (RE = Y­(<b>9</b>), Er­(<b>10</b>)). In the presence of cocatalysts, the rare-earth metal monoalkyl complexes initiated isoprene polymerization with a high activity (90% conversion of 1000 equiv of isoprene in 25 min) producing polymers with high regio- and stereoselectivity (1,4-cis polymers up to 99%)