Organometallics最新文献

While base metal-catalyzed cross-couplingsof alcohols and (hetero)arylchlorides have emerged over the past decade, the development of asingle pre-catalyst capable of promoting such transformations spanningall of primary, secondary, and tertiary (aliphatic) alcohols remainsan enduring challenge. Herein we disclose the easily prepared, air-stable4-cyanophenyl pre-catalyst (L2)Ni(4-CN-Ph)Cl (L2 = CgPhen-DalPhos), which is shown to be capable of promoting, withuseful reaction scope, the C–O cross-coupling of all such alcoholclasses with (hetero)aryl chlorides.

The reactivity of[Ru₃(CO)₁₀(μ-dppf)](1) [dppf = 1,1′-bis(diphenylphosphino)ferrocene]toward internal alkynes, RC≡CR (R = Et, Ph,CO₂Me, CO₂Et), has been explored. Isolated productsvary with the nature of the alkyne substituent and differ from thosegenerated with related diphosphine-stabilized triruthenium clusters.In all products, one or two equivalents of alkyne are incorporatedand three or four carbonyls are lost. With hex-3-yne, the allenylcluster [Ru₃(CO)₇(μ-H)(μ-dppf)(μ₃-η¹:η²:η²-MeCHC≡CEt)] (2) results via aliphatic C–Hbond activation of one of the ethyl groups. With diphenylacetylene,the major product is [Ru₃(CO)₆(μ-H){μ-Ph₂P(C₅H₃)Fe(C₅H₄)PPh₂}(μ₃-η¹:η¹:η²-PhC₂Ph)] (3)which contains a capping alkyne ligand and a metalated dppf ligand,formed via C–H activation of one of the cyclopentadienyl rings.Metalation results in formation of a dative Fe–Ru bond. Withactivated alkynes (RCO₂)C₂(CO₂R)(R = Me, Et), alkyne coupling occurs to afford theopen 52-electron clusters [Ru₃(μ-CO)(CO)₆(μ-PPh₂){μ-η¹:κ¹-Ph₂P(C₅H₄)Fe(C₅H₄)}{μ₃-η¹:η²:η²:κ¹-C₄(CO₂R)₄}] (4–5). The later containbridging phosphido (PPh₂) and chelating Ph₂PFe(C₅H₄)₂ ligands, formed via a previouslyunreported P–C bond cleavage of the coordinated dppf ligand.All four new clusters have been characterized by single-crystal X-raydiffraction studies. We discuss likely reaction pathways and why thesetransformations differ so much as a function of the appended diphosphineligand.

Metal complexes featuring secondary amine donors havebeen extensivelystudied in the context of hydrogen-bonding or metal–ligandcooperative interactions. In this regard, pincer-type ligand frameworkshave been described, but macrocyclic variants remain rare. Herein,we describe the synthesis of macrocyclic carbene ligand frameworksfeaturing a carbazolide backbone and an ether or secondary amine donor.While the ether was synthesized through conventional methods, theamine variant required microwave heating. Carbazolide-bis(imidazolium)pro-ligands were isolated as air-stable compounds. Metalation withCu(acac)₂ led to the formation of square-planar Cu(II)complexes characterized by single-crystal X-ray diffraction and cyclicvoltammetry. A significantly more cathodic Cu(I)/Cu(II) wave by 330mV was observed for the amine complex. Combined, the results highlightnew macrocyclic carbene platforms with variable coordination environments.

The rational design of constrained geometry catalysts(CGCs) forolefin polymerization remains challenging due to the intricate interplaybetween steric and electronic effects and the prohibitive computationalcost of exploring large chemical spaces using quantum-chemical methods.In this work, we develop a mechanistically informed machine learningframework that bridges semiempirical GFN2-xTB descriptors with densityfunctional theory (DFT)-computed activation barriers for ethyleneinsertion. DFT calculations identify the first insertion as the rate-determiningstep (RDS), enabling construction of a physically motivated surrogatemodel based on the cationic methyl active species. Benchmarking acrosseight regression algorithms identifies Gradient Boosting Regressoras the optimal predictor, delivering DFT-comparable predictive accuracywhile reducing computational cost by several orders of magnitude.SHapley Additive exPlanations analysis reveals that metal electrophilicityis the primary factor governing the activation barrier of the RDS,providing direct mechanistic interpretation of the learned structure–activityrelationships. Application of the model to a virtual library of approximately1.4 × 10⁵ chemically valid CGCs via a high-throughputvirtual screening workflow rapidly identifies low-barrier candidatesand uncovers robust design principles, particularly the beneficialrole of electron-donating cyclopentadienyl substituents. The presentframework establishes an interpretable and efficient paradigm foraccelerated polyolefin catalyst discovery.

Chiral dienes and N-heterocyclic carbenes(NHC)are important ligands for transition-metal catalysis. Surprisingly,both ligand classes are rarely employed together in Rh complexes.To get more detailed insight into the interaction between NHC anddiene ligand simultaneously coordinated to the same Rh center, a seriesof eight neutral Rh diene NHC complexes, [Rh(L1)(NHC)Cl] (NHC = ICy,IMes, IⁱPr, IPr, SIPr, IMe, (R)-IEtPh, and (S)-IEtPh), and four cationic analogues,[Rh(L1)(NHC)]X (NHC = ICy, IMes, IPr: X = B(Ar^F)₄; NHC = ICy: X = SbF₆), were synthesized from [Rh(L1)Cl]by three complementary synthetic routes and anion exchange. X-raycrystal structure analyses revealed pronounced NHC-dependent distortionsfrom a square-planar geometry in neutral complexes, whereas cationicspecies remain comparatively rigid. Catalytic studies showed a strongdependence on the NHC ligand’s identity: while NHC incorporationgenerally reduced yields and enantioselectivities in asymmetric 1,2-and 1,4-additions, the cationic complex [Rh(L1)(ICy)]SbF₆ delivered improved activity and selectivity in 1,6-enyne cycloisomerization,consistent with reduced catalyst deactivation as confirmed by kineticanalysis. DFT calculations identified that stereocontrol originatesfrom key interactions enforced by the chiral diene scaffold, disruptedby bulkier NHC ligands. These findings highlight the decisive influenceof NHC sterics on the structure, stability, and asymmetric reactivityof Rh diene catalysts.

Benzene rings are among the most frequently encounteredring systemsin small-molecule drugs, but only a few substitution patterns (1-,1,2-, 1,4-, and 1,2,4-) predominate. Here, regioselective nickel-catalyzedthree-component cyclotrimerization of terminal alkynes and phenylvinyl sulfone was used to synthesize an underrepresented substitutionpattern, the 1,3-arene. Phenyl vinyl sulfone serves as an acetylenesurrogate for the regiocontrolled synthesis of meta-terphenyl derivatives. The reaction demonstrated wide functionalgroup tolerance with moderate to good yields. Stoichiometric reactivitystudies with catalytically relevant nickel complexes established themechanistic origin of the observed regioselectivity.

Post-transition state bifurcations (PTSBs) previouslyhave beenidentified in dirhodium-catalyzed C–H insertion reactions thatform β-lactones, where a single transition structure providesdirect access to both insertion and fragmentation products. Here,we investigate whether this behavior is a general feature of metal-catalyzedC–H insertion reactions by extending the analysis to iridium-and ruthenium-based catalysts, amide (lactam-forming) substrates,and metal-free carbene reactions. Using quantum chemical calculations,ab initio molecular dynamics (AIMD) simulations, and principal componentanalysis (PCA)-based potential energy surface (PES) construction,we demonstrate that PTSBs are present across all types of metal-catalyzedsystems examined. Catalyst identity influences PES topography andproduct selectivity, with iridium-based systems showing greater selectivityfor lactone formation than ruthenium-based systems. For amide substrates,fragmentation proceeds via a two-step pathway through a discrete intermediatenot observed in the ester series. Collectively, these results establishPTSBs as a general feature of the reaction landscape for metal-catalyzedC–H insertion reactions that form 4-membered rings.

The reactions between [Cp*₂Ln(allyl)] and [(dppe)Ni(SH)₂] (dppe = Ph₂PCH₂CH₂PPh₂) or [(POCOP^iPr)Ni(SH)](POCOP^iPr =C₆H₃(OP(ⁱPr)₂)₂) proceed as a classic acid–base interactionin which the nickel hydrosulfide complexes serve as typical Brønstedacids. In case of the dibasic acid [(dppe)Ni(SH)₂] thereactions lead to tetrametal coordination clusters [{(dppe)Ni}₂(μ₃-S)₄{LnCp*}₂] (Ln= Dy (1), Ho (2)) and accompanied by eliminationof propene and Cp*H, while in case of monobasic acid [(POCOP^iPr)Ni(SH)] only (allyl)⁻ serves as a proton acceptorand the reactions result in formation of bimetal species [(POCOP^iPr)Ni(μ-S){LnCp*₂}] (Ln = Dy (3), Ho (4), Y (5)). Single-crystal X-raydiffraction (XRD) revealed correspondingly tetrametal and dimetalsulfido-bridged Ni/S/Ln frameworks, with the binuclear complexes exhibitingexceptionally short Ln–S bond distances. Magnetic measurementsof the Ni/Dy and Ni/Ho complexes showed that the Ni(II) centers arediamagnetic and that the magnetic behavior is governed by correspondinglanthanide ion(s). For 3 field-induced slow magneticrelaxation was observed, with an effective relaxation barrier of 22K.

Compared with mononuclear catalysts, dinuclear catalystsoftenexhibit synergistic effects between their two metal centers, offeringunique advantages in enhancing catalytic performance. In this work,an alkyl elimination strategy was employed to synthesize novel arylamidomono- and dinuclear scandium bis(alkyl) complexes. The phenyl-bridgedarylamido ancillary ligands (2,6-ⁱPr₂C₆H₃)NH(C₆H₄)NH(C₆H₃-2,6-ⁱPr₂) (HL¹) and [4,4′-(2,6-ⁱPr₂C₆H₃NH)₂][C₆H₄]₂ (HL²) were reacted with Sc(CH₂SiMe₃)₃(THF)₂ in a 1:2 molar ratio in THF,yielding the corresponding dinuclear complexes [1,4-(2,6-ⁱPr₂C₆H₃N)₂(C₆H₄)][Sc(CH₂SiMe₃)₃(THF)]₂ (1) and [4,4′-(2,6-ⁱPr₂C₆H₃N)₂(C₆H₄)₂][Sc(CH₂SiMe₃)₂(THF)₂]₂ (2). To investigate the differences in polymerization performancebetween mononuclear and dinuclear complexes, the mononuclear arylamidoscandium bis(alkyl) complex [(2,6-ⁱPr₂C₆H₃)N(C₆H₅)]Sc(CH₂SiMe₃)₂(THF) (3) was preparedby reacting (2,6-ⁱPr₂C₆H₃)NH(C₆H₅) (HL³) with Sc(CH₂SiMe₃)₃(THF)₂ in a 1:1 molar ratio in hexane. Allcomplexes were characterized by NMR spectroscopy and elemental analysis.Furthermore, the molecular structures of complexes 1 and 2 were unambiguously determined by single-crystal X-ray diffraction.All complexes were able to initiate the ring-opening polymerization(ROP) of trimethylene carbonate (TMC) with high activity under mildconditions. Compared to the mononuclear complex 3, complex 1 displayed a distinct dinuclear synergistic effect on TMCpolymerization. Complex 1 enabled the ROP of TMC in amolecular-weight-controllable manner, allowing for the synthesis ofhigh-molecular-weight PTMC (M_n > 10⁵ g/mol) by tuning the monomer-to-initiator molar ratio.

A base-free, microwave-assisted protocol using Cu₂Oand NHC·HCl salts is reported, which allows the synthesis ofsterically less hindered 2-alkylphenyl-substituted (NHC)CuCl complexes,(SIMe^ortho)CuCl, (SIPr^ortho)CuCl, (IMe^ortho)CuCl and (IPr^ortho)CuCl; the use of dichloromethane inplace of conventionally used tetrahydrofuran as a solvent is the keyto success. Structural and NMR analyses show that 2-alkylphenyl substitutionefficiently modulates the steric properties of the (NHC)CuCl complexeswhile largely preserving the electronic properties of the NHC ligands.This work offers a useful strategy for designing diverse NHC ligands,providing a straightforward approach to sterically tunable (NHC)CuClcomplexes.