Organometallics最新文献

A one-pot strategy has been applied to access the cyclohexyl-fused 2-arylimino-1,10-phenanthroline-iron(II) complexes, [(L_Ph)₂Fe][FeCl₄] (Fe1) and (L_aryl)FeCl₂ (aryl = 2,6-F₂Ph Fe2, 4-FPh Fe3, 4-MePh Fe4, 2,6-Me₂Ph Fe5, 2,6-Et₂Ph Fe6, 2,6-i-Pr₂Ph Fe7, 2-FPh Fe8, 2-MePh Fe9), that differ in the steric/electronic profile of their N-aryl groups and the number of N,N,N-chelating ligands per iron. Structural characterization of Fe3, Fe5, Fe6, and Fe9, along with the ligand-oxidized species Fe5′ and Fe6′, highlights the distorted square pyramidal geometry about the iron centers and the flexibility/sensitivity of the fused carbocyclic ring. While bis(chelate) Fe1/MAO proved almost inactive for ethylene oligomerization, the majority of the mono(chelate) iron complexes exhibited high to moderate levels of activity under MAO activation. Indeed, the most active system, ortho-methyl Fe9/MAO, attained a level of 3.78 × 10⁶ g oligomer mol^–1 (Fe) h^–1 displaying >99% selectivity for linear α-olefins (C₄–C₁₄+) that follow a Schulz–Flory distribution. When compared to the prototypical 2-imino-1,10-phenanthroline-iron oligomerization catalysts, the current fused systems are less active but are capable of suppressing the formation of polyethylene wax. We attribute this finding to the more open space displayed by the active iron center when compared to that seen in the parent system, leading to more facile β-H elimination.

The reaction of Ni(COD)₂ with [PhC(NtBu)₂SiSi(SiMe₃)₃] (1) in toluene results in the formation of an 18-electron silylene-Ni(0) toluene complex (2). The analogous reaction with 1,3-DFB instead of toluene affords the C–H activation followed by ring walking leading to the allylic cyclooctene adduct, the (η³-C₈H₁₃)Ni(II) complex (3). DFT calculations were carried out to elucidate the mechanism as well as to gain insight into why 1,3-DFB undergoes C–H bond activation instead of C–F bond activation. The use of NiCl₂·DME permits access to 16-electron (tetrylene)₂NiCl₂ (Si(4) and Ge(5)) species, and 4 was later used as a catalyst for the C–N coupling reaction.

Polynuclear complexes of rare earth metals Sc, La, Nd, Sm, Er, Yb with anthracenylboronic acid (AntB(OH)₂) and pyrenylboronic acid (PyrB(OH)₂) as a ligands were synthesized by reactions of cyclopentadienyl metal complexes LnCp₃ with the corresponding arylboronic acid. X-ray structural analysis of Nd, Sm and Er complexes revealed that obtained compounds are dimers, in which each metal atom is coordinated by two terminal Cp ligands and two bridging arylboronic acid fragments. Scandium complex is a tetranuclear compound that contains four anthracenylboronic acid ligands and four Cp-ligands. Lanthanum complex is a trinuclear coordination compound comprising three La³⁺ cations linked by three bridging anthracenylboronate anions. Photoluminescence spectra of Sc and La derivatives in the solid state showed excimer ligand emission in the region 350–650 nm. The Nd, Er and Yb complexes exhibited NIR metal-centered photoluminescence of the corresponding metal ion.

Cyclic alkyl amino iminate (CAAI) phosphines were synthesized in good yields via chlorophosphine/(CAAI)TMS exchange. These ligands adopt a conformation in which the methyl groups on the CAAI unit are oriented toward the metal center, enabling potential weak C–H···metal interactions, as characterized by experimental and computational methods. CAAI phosphines have been applied in Pd-catalyzed ketone arylation, showing promising reactivity with electron-rich substrates. These findings establish CAAI phosphines as a class of flexible ligand for transition-metal-catalyzed transformations.

Chemical reduction of the previously reported Cr(II) chloride dimer supported by a bulky imidazolin-2-iminato ligand, [Cr(μ₂-NIm^Dipp)(Cl)]₂, affords the Cr(I) dimer [Cr(μ₂-NIm^Dipp)]₂ (1) in moderate crystalline yield (NIm^Dipp = 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-iminato, Dipp = 2,6-diisopropylphenyl). Single-crystal X-ray diffractometry analysis of 1 reveals a Cr₂N₂ diamond core structure by two bridging iminato ligands and a strong η⁶ interaction between the Cr(I) ion and one of the flanking Dipp group. A salient feature in 1 is the long Cr···Cr distances of 2.7274(5) and 2.6548(4) Å. Complex 1 is diamagnetic in solution at 300 K, suggesting that the Cr(I) ions have a strong antiferromagnetic interaction. Both unrestricted and broken symmetry density functional theory calculations indicate that 1 has two low-spin (S = ¹/₂) Cr(I) ions with a very large antiferromagnetic exchange coupling constant (J), resulting in a diamagnetic ground state at 300 K.

The chemistry of antimony-based radicals remains significantly less developed in comparison to that of phosphorus radicals. Herein we report the synthesis and characterization of radical anions derived from stibinidene sulfide and selenide via one-electron reduction. Electron paramagnetic resonance spectroscopy combined with density functional theory calculations revealed that the unpaired electron predominantly occupies the π* antibonding orbitals of the Sb═S and Sb═Se double bonds with notable localization on the antimony center.

A series of Ru(L)(X)₂ complexes (L = bidentate ligand; X = OMs, OTs, OTf) was synthesized and characterized. Ru(BINAP)(OMs)₂ showed improved catalytic performance over the established Ru(BINAP)(OAc)₂ catalyst, highlighting the impact of anion variation on catalytic asymmetric hydrogenations.

While most reported Co(-I) complexes are coordinatively saturated, we report herein a 16e^– Co(-I) complex [(cyIDep)Co(η²-vtms)(N₂)Na(OEt₂)]₂ (where cyIDep = 1,3-di(2′,6′-diethylphenyl)-4,5-(CH₂)₄-imidazol-2-ylidene; and vtms = vinyltrimethylsilane). The Co(-I) complex is isolated from the reaction of [(cyIDep)Co(η²-vtms)₂] with sodium under a dinitrogen atmosphere. It features short Co–N (1.695(3)/1.695(3) Å) and long N–N bonds (1.166(4)/1.168(3) Å). Theoretical study indicates the presence of 2-fold Co-to-N₂ π-backdonation interactions in the three-coordinate Co(-I) species, which might lead to thermodynamic gains to the unusual alkene-to-N₂ ligand exchange reaction that gives the Co(-I) complex. The attempts to functionalize the dinitrogen ligand in the Co(-I) complex with Me₃SiCl and a N-heterocyclic silylene lead to the isolation of the cobalt(I) alkyl complex [(cyIDep)Co(C(SiMe₃)₂Me)] and the cobalt(0) complex [(^t-BuNHSi)(cyIDep)Co(η²-vtms)] (^t-BuNHSi = 1,3-bis(tert-butyl)-1,3-diaza-2-silacyclopent-4-en-2-ylidene), respectively, rather than the desired products.

Three new lanthanide complexes of the general form [Ln(Cnt)(CntInd)] (Ln = Ce, Pr, and Nd; Cnt = cyclononatetraenyl; and CntInd = cyclononatetraenyl-dihydroindene) have been synthesized from the corresponding LnI₃ salt and several equivalents of the KCnt ligand. A novel C–C coupling has been observed between one Cnt^– moiety and one dihydroindene moiety, originating from the collapse of a Cnt unit. The observed CntInd ligand is dianionic, harboring one more electron than a typical Cnt ligand. The complexes are characterized by X-ray diffraction, ¹H NMR, and UV–visible studies. The novel complexes are formed instead of the [Ln(Cnt)₃] (Ln = Ce, Pr, and Nd), which are only reported with late lanthanide ions, while lanthanum did not form one or the other complex.

The synthetic utility of alkyne metathesis remains underdeveloped compared to olefin metathesis, its mechanistic analogue. Advancement in tridentate molybdenum alkylidyne catalysts led to an expanded substrate scope and enhanced stability. However, the systematic tuning of their steric and electronic properties has not yet been realized. Here, we report a library of adaptive tridentate ligands with a tris(biphenyl)methane backbone. A total of 35 ligands were prepared using a modular synthetic strategy, all of which were active in metathesis upon ligand exchange with a precatalyst cat-II, and 12 of them demonstrated activity surpassing that of the fastest monodentate and tridentate ligands in literature. Density functional theory (DFT) calculations suggested that their reactivity originated from the highly adaptive ligand backbone, which could accommodate different coordination geometries with minimal strain. A systematic survey established that steric factors outweigh electronic properties, and the highest reaction rates were achieved for ligands with medium-sized meta-substituents or bulky para-substituents. The catalysts demonstrated moderate stability and retained full activity after 2 h of open vial storage in air. Anthraquinone-bearing L-CP21 features a rather broad substrate scope, promoting the metathesis of challenging substrates bearing cyano, nitro, aldehyde, aniline, pyridine, and pyrimidine groups with excellent isolated yields.