Organometallics最新文献

Chlorinating the backbone of N-heterocyclic carbene ligands (i.e., NHC^Cl) yielded Pd catalysts (i.e., Pd-NHC^Cl) with dramatically improved performance in cross-coupling catalysis. Unexpectedly, precatalysts of the type PdCl(cinnamyl)(NHC^Cl) at low catalytic loading (0.1 mol %) turned out to be not applicable in Buchwald-Hartwig C–N coupling with alkylamines. This is caused by the reaction of the precatalyst with alkylamines, leading to free NHC^Cl and PdCl(cinnamyl)(alkylamine); similar reactivity was observed with ammonia. PdCl(cinnamyl)(alkylamine) is not activated to a zerovalent Pd species; therefore, catalysis cannot begin. Other precatalysts, like PdCl₂(morpholine)(NHC^Cl) and PdCl₂(3-chloropyridine)(NHC^Cl) (Pd-PEPPSI-NHC^Cl), as well as precatalysts of the type PdCl(cinnamyl)(NHC) bearing nonchlorinated ligands, are stable under these conditions, activated, and perform well in catalytic C–N coupling.

A 9,10-distiba-Dewar-anthracene bearing bulky substituents was obtained by the reduction of the corresponding 5,10-dichloro-5,10-dihydrostibanthrene. Molecular structures of the 9,10-distiba-Dewar-anthracene and 5,10-dichloro-5,10-dihydrostibanthrene have been definitively revealed by single-crystal X-ray crystallographic analyses and discussed based on theoretical calculations. Computational studies suggest that 9,10-distiba-Dewar-anthracene is thermodynamically favorable relative to the corresponding 9,10-distibaanthracene derivative.

Iridium complexes bearing the 1-hydroxy-tetraphenyl-cyclopentadienyl (^4PhCpOH) ligand, such as Ir(^4PhCpOH)H₂PPh₃ (Ir1), uniquely enable high aromatic selectivity in HDO of phenolic and methyl ether lignin model compounds [Kusumoto, S.; Nozaki, K.. Nat. Commun. 2015, 6, 6296.]. Mechanistic studies suggest that intact Ir1 may be active in HDO of naphthols, while phenyl phenols require initiation to yet unknown species [Gjermestad, C. S. . Organometallics 2025, 44 (3), 536–546.]. To probe possible active species, we evaluated IrH(COD)(PPh₃)₂ (Ir2, COD = cyclooctadiene) and [IrCl(^4PhCp═O)]_n (Ir3), accessible precursors to complexes resembling those formed via dissociation of ^4PhCpOH or PPh₃ from Ir1. Neither Ir2 nor Ir3 replicated Ir1’s full reactivity, but Ir2, a neutral analogue of the Crabtree catalyst, matched Ir1’s activity in HDO of 1-naphthol, with a mercury test suggesting the presence of a molecular catalyst. Density functional theory (DFT) analysis revealed a pathway for Ir2-catalyzed HDO of 1-naphthol mirroring Ir1: substrate-assisted keto–enol tautomerization, Ir-catalyzed reduction, substrate-assisted dehydration, and final (de)hydrogenation by Ir. The predicted preference for dehydrogenation aligns with observed naphthalene selectivity. While the species active for phenyl phenols remains unidentified, the parallels between Ir1 and Ir2 in HDO of 1-naphthol offer insights for designing future catalysts combining structural simplicity, accessibility, and broader substrate scope.

As one of the most important N-containing polycyclic aromatic hydrocarbons, benzimidazo[2,1-a]isoquinoline derivatives are of great interest due to their unusual biological activities and photophysical properties. Herein, we present the S_NAr reaction of osmabenzene with 1-aminoisoquinoline to access unique metal-containing benzimidazo[2,1-a]isoquinoline derivatives. Comprehensive DFT calculations, including NICS, AICD, EDDB, and NOBD analysis, reveal the aromaticity switching of the osmabenzene ring of the resulting osmabenzimidazoisoquinolines. Additionally, these conjugated condensed metallacycles exhibit effective narrowing of the HOMO–LUMO gap, resulting in red-shifted absorption bands.

Ligand-to-metal charge transfer (LMCT) states have significant potential to drive diverse photochemical transformations but remain underexplored compared with other charge-transfer processes. In this work, we report bench-stable, low-hygroscopic Fe(III) homo-bimetallic complexes of the type [L][FeX₄] (where, L = 4′-ferrocenyl-6,6″-di(piperidin-1-yl)-2,2′:6′,2″-terpyridine, X = Cl, Br) that function as efficient photocatalysts for atom transfer radical polymerization of acrylate monomers. The ion-pair combination of the catalyst enables access to a low-energy LMCT state that initiates the photopolymerization. Time-dependent density functional theory analysis shows an interionic charge transfer from the donor orbitals of the cationic moiety to the antibonding orbitals of the anionic FeX₄^̅, which leads to Fe–X bond homolyses in the excited state. The LMCT-assisted pathway drives controlled radical polymerization under mild conditions to achieve well-defined acrylate polymers.

A hydrogermylyne-bridged W₂Ge₂ cluster 1, stabilized by N-heterocyclic carbene (NHC), was synthesized by the reaction of a hydrido(hydrogermylene) complex with an excess of 1,3,4,5-tetramethylimidazol-2-ylidene (^MeIMe). X-ray diffraction analysis revealed a planar and rhombic four-membered W₂Ge₂ ring framework with a relatively short diagonal Ge···Ge distance (∼2.74 Å). Each Ge atom bears a Ge–H bond, representing the first example of this bonding motif. The extremely high-field-shifted ¹H NMR signal (1.59 ppm) of the Ge–H proton and DFT calculations including QTAIM and NICS-rate analyses suggest a significant electron delocalization over the W₂Ge₂ ring.

Bulky phosphino substituents, such as ^tBu₂P, are key components of ligands in homogeneous catalysis, yet few options exist to tune their electronic properties while retaining comparable steric environments. Here, we report the synthesis of oxo-tetramethylphosphinane (oxo-TMPhos), a 2° phosphorinone scaffold that incorporates a γ-ketone substituent into the tetramethylphosphinane framework. The ketone handle enables broad derivatization, including reduction, amination, and C–C bond formation, while the 2° phosphine can be used to construct a variety of ligands. Systematic donor strength evaluation using the Huynh electronic parameter (HEP) confirmed that phosphorinones are weaker donors than tetramethylphosphinane (TMPhos) and ^tBu₂PH, reflecting the electron-withdrawing C═O substituent. From this scaffold, we prepared a series of phosphorinone ligands, including Buchwald-type, bidentate phosphines with propyl (BPP) or butyl (BPB) linkers, bulky PCP and PNP pincer ligands, and a new scalable route to bis(2,2,6,6-phosphorin-4-one)-o-xylene (BPX). In Pd-catalyzed isomerizing methoxycarbonylation of 4-octene, BPP delivered over an order of magnitude higher turnover numbers (TONs) than the corresponding di-tert-butylphosphino analogue. It could be applied across a broad substrate scope, including internal, branched, cyclic, and styrenic alkenes. This work highlights phosphorinones as a practical and tunable alternative to classical bulky alkylphosphines, with significant potential for applications in homogeneous catalysis.

A novel nitronyl nitroxide organocopper derivative has been reported─a unique reagent for cross-coupling reactions of aryl and heteroaryl halides. The innovative protocol involves a copper complex supported by a sterically hindered NHC ligand, specifically SIPrCuNN, and a Pd(0)-catalytic system resulting from Pd₂dba₃·CHCl₃ and the phosphine ligand ^MeCgPPh. The designed method is compatible with various aromatic and heteroaromatic iodides, therefore increasing new applications for creating functionalized nitronyl nitroxide paramagnet and open-shell compounds.

We report the ethenylation of 1,3- and 1,2-disubstituted benzenes using [(η²-C₂H₄)₂Rh(μ-OAc)]₂ as a catalyst precursor and Cu(OPiv)₂ as the oxidant. The regioselectivity of alkenylation for 1,3-disubstituted benzenes produces 3,5-disubstituted styrene products, while the alkenylation of 1,2-disubstituted benzenes produces 3,4-disubstituted styrene products. The rate of alkenylation is influenced by steric and electronic factors based on the substituents of the benzene unit. In all cases, 1,2-disubstituted benzenes react faster than 1,3-disubstituted benzenes, with a rate difference that is from 2 times up to >70 times more rapid for 1,2-disubstituted substrates. This is likely due to the difference in the number of accessible C–H bonds based on the steric protection of C–H bonds adjacent to functionality. Furthermore, the rate of alkenylation is influenced by the arene substituent electronics. The rates of alkenylation for 1,2-disubstituted benzenes follow the trend OMe > Me > CF₃ > Cl, while for 1,3-disubstituted benzenes the trend is CF₃ > Cl > Me > OMe. Using quantum mechanics DFT calculations, we found that the C–H activation step can occur by two different mechanisms. The electronic properties of substituents on the arene ring change the preferred C–H bond-breaking mechanism for 1,2-disubstituted and 1,3-disubstituted benzenes.

An enantioselective hydrogenation of a fluorinated cyclobutenoic acid derivative using both neutral cobalt(II) and cationic, bis(phosphine)-supported cobalt(I) precatalysts has been developed. With 2 mol % of [((S,S)-^PhBPE)Co(η⁶-PhMe)][BAr^F₄], complete conversion and >99% ee was obtained at ambient temperature, enabling a route for the preparation of an enantioenriched bis(difluoro)-substituted cyclobutane. Deuterium-labeling studies supported homolytic cleavage of H₂ and established the unsaturated starting material was not isomerized under catalytic hydrogenation conditions.