Rare-Earth Metalloligands for Low<b>-</b>Valent Cobalt Complexes: Fine Electronic Tuning <i>via</i> Co→RE Dative Interactions

Rare-earth metalloligand supported low-valent cobalt complexes were synthesized by utilizing a small-sized heptadentate phosphinomethylamine LsNH3 and a large-sized arene-anchored hexadentate phosphinomethylamine LlArH3 ligand precursors. The RE(III)-Co(−I)-N2 (RE = Sc, Lu, Y, Gd, La) complexes containing rare-earth metals including the smallest Sc and largest La were characterized by multinuclear NMR spectroscopy, X-ray diffraction analysis, electrochemistry, and computational studies. The Co(−I)→RE(III) dative interactions were all polarized with major contributions from the 3dz2 orbital of the cobalt center, which was slightly affected by the identity of rare-earth metalloligands. The IR spectroscopic data and redox potentials obtained from cyclic voltammetry revealed that the electronic property of the Co(−I) center was finely tuned by the rare-earth metalloligand, which was revealed by variation of the ligand systems containing LsN, LmN, and LlAr. Unlike the direct alteration of the electronic property of metal center via an ancillary ligand, such a series of rare-earth metalloligand represents a smooth strategy to tune the electronic property of transition metals

Rare-Earth Metalloligands for Low<b>-</b>Valent Cobalt Complexes: Fine Electronic Tuning <i>via</i> Co→RE Dative Interactions

Rare-earth metalloligand supported low-valent cobalt complexes were synthesized by utilizing a small-sized heptadentate phosphinomethylamine LsNH3 and a large-sized arene-anchored hexadentate phosphinomethylamine LlArH3 ligand precursors. The RE(III)-Co(−I)-N2 (RE = Sc, Lu, Y, Gd, La) complexes containing rare-earth metals including the smallest Sc and largest La were characterized by multinuclear NMR spectroscopy, X-ray diffraction analysis, electrochemistry, and computational studies. The Co(−I)→RE(III) dative interactions were all polarized with major contributions from the 3dz2 orbital of the cobalt center, which was slightly affected by the identity of rare-earth metalloligands. The IR spectroscopic data and redox potentials obtained from cyclic voltammetry revealed that the electronic property of the Co(−I) center was finely tuned by the rare-earth metalloligand, which was revealed by variation of the ligand systems containing LsN, LmN, and LlAr. Unlike the direct alteration of the electronic property of metal center via an ancillary ligand, such a series of rare-earth metalloligand represents a smooth strategy to tune the electronic property of transition metals

Aluminum Complexes Bearing N‑Protected 2‑Amino- or 2‑Imino-Functionalized Pyrrolyl Ligands: Synthesis, Structure, and Catalysis for Preparation of Pyrrolyl-End-Functionalized Polyesters

Reactivity of N-protected 2-amino- or 2-imino-functionalized pyrroles with aluminum alkyls was investigated, resulting in the isolation of a series of aluminum alkyl complexes. Treatment of 2-imino-functionalized pyrrole with AlMe₃ produced only imino-coordinated aluminum complex 1-Bn-2-(2,6-^<i>i</i>Pr₂C₆H₃NCH)­C₄H₃NAlMe₃ (<b>1</b>), while reactions of N-protected 2-amino-functionalized pyrroles with aluminum alkyls produced the aluminum alkyl complexes {[η¹-μ-η¹:η¹-1-R₁-2-(2,6-^<i>i</i>Pr₂C₆H₃NCH₂)­C₄H₂N]­AlR}₂ (R₁ = Bn, R = Me (<b>2</b>); R₁ = Bn, R = Et (<b>3</b>); R₁ = R = Me (<b>4</b>); R₁ = Me, R = Et (<b>5</b>)), bearing 3-carbon bonded pyrrolyl ligands via C–H σ-bond metathesis reaction. Further reactions of complexes <b>2</b>–<b>5</b> with a stoichiometric amount of isopropyl alcohol (^<i>i</i>PrOH) afforded the corresponding aluminum alkoxide complexes [1-R₁-2-(2,6-^<i>i</i>Pr₂C₆H₃NCH₂)­C₄H₃NAlR­(μ-O^<i>i</i>Pr)]₂ (R₁ = Bn, R = Me (<b>6</b>); R₁ = Bn, R = Et (<b>7</b>); R₁ = R = Me (<b>8</b>); R₁ = Me, R = Et (<b>9</b>)) through selective cleavage of the Al–C (Pyr) bonds. The solid-state structures of the aluminum complexes <b>1</b>–<b>6</b> and <b>8</b> were confirmed by an X-ray diffraction study. These aluminum alkyl complexes exhibited notable activity toward the ring-opening polymerization of ε-caprolactone and l-lactide in the absence of alcohol. The end group analysis of the ε-CL oligomer gave strong support that the polymerization proceeded via a coordination–insertion mechanism involving a unique Al–C (Pyr) bond initiation, providing pyrrolyl-end-functionalized polyesters

Indolyl-based Copper(I) Complex-Catalyzed Intermolecular Trifluoromethylazolation of Alkenes via Radical Process

Herein, we synthesized and characterized a binuclear copper(I) complex supported by the indolyl-based ligand. Employing this complex as catalyst, we have developed a three-component intermolecular trifluoromethylazolation of alkenes to deliver various trifluoromethylated azole derivatives. The method features exclusive chemo- and regioselectivity, a broad scope of alkenes and oxazoles, thiazoles, and good tolerance of functional groups under mild conditions. Preliminary mechanistic studies support a radical process for the transformation

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