Once considered a “laboratory curiosity”, cyclic borenium ions have recently been shown to exhibit tunable emission and stimuli-responsive properties. Utilizing hexaphenylcarbodiphosphorane (CDP), a series of borafluorenium and 3,3′-dimethoxyborafluorenium ions were synthesized to determine the impacts of counteranion and substituent effects on the optical properties and stability of borafluorenium ions. Clear relationships were established between structure and properties, with emission wavelengths of the borafluorenium ions ranging from yellow (λ_em = 559 nm) to red (λ_em = 650 nm). By employing density functional theory, a possible mechanism for the observed luminescent behavior was proposed. These compounds were shown to exhibit aggregation-induced emission (AIE) properties and significant changes in solid-state emission color when compared to those observed in solution. The AIE properties of a CDP–borafluorenium ion with dimethoxy substitution were further explored by perturbing the temperature in solution, which resulted in a clear shift in emission wavelength from 563 nm (yellow, 20 °C) to 513 nm (green, −90 °C).

The Zincke reaction combines a pyridinium salt bearing an N-withdrawing group and a primary aliphatic amine to form an alkylated pyridinium salt through a ring-opening/ring-closing sequence. Herein, we explore the analogous reaction sequence for a pyridinium salt η²-bound to a transition metal. We find that the N-sulfonylated pyridinium ligand (pyR¹, where R¹ = mesyl or tosyl) of [WTp(NO)(PMe₃)(η²-pyR¹)]OTf selectively reacts with a primary amine, and the resulting 2-aminodihydropyridine complex then undergoes a tungsten-stabilized ring-scission to form the corresponding η²-azatriene complex. Subsequent ring-closure between the newly installed amine and the sulfonylated imine results in a new aminodihydropyridinium species. This dihydropyridinium resists rearomatization due to a stabilizing influence of the tungsten fragment. Subsequent displacement of the sulfonamide by pendent heteroatoms leads to the formation of new heterocyclic frameworks. Herein the syntheses of 30 heterocyclic complexes are described (3 characterized by SC-XRD) including 7 examples of multicyclic systems.

From the reaction of a high-valent Sb(V) proligand with a low-valent Ir(I) precursor in acetonitrile, a bimetallic Sb–Ir complex was isolated in which one of the quinoline groups inverted such that it is N-coordinated to Sb and C-coordinated to Ir. The new Sb–Ir complex has a unique structure containing the shortest reported Sb–Ir bond (2.51502(18) Å). Our combined experimental and computational studies indicate pronounced covalent character for the Sb–Ir bond. Based on the covalent bonding, the complex more closely resembles Sb(IV)–Ir(II) species rather than Sb(V)–Ir(I) and thus results in an Ir center with poor π-basicity, particularly toward the position trans to Sb.

The emerging field of dearomatization capitalizes on the synthetic potential of aromatic molecules. By using a transition metal to bind to two carbons of a benzene ring, the remaining four carbons are left available for the attachment of various chemical fragments. If these fragments are connected, this process could be a blueprint for synthesizing polycyclic architectures. The objective of this study is to develop a modular approach for creating classes of saturated polycyclic compounds that are currently underrepresented in the landscape of druggable chemical space. Herein, the phenyl group of methylphenylsulfone is coordinated to the tungsten complex {WTp(NO)(PMe₃)}, largely interrupting its aromatic stabilization because of strong metal-to-ligand backbonding. Through the combination of ester enolate and amine addition reactions to the arene carbons, a wide array of chemically diverse polyheterocyclic systems is prepared. The tungsten stereogenic center influences the configurations of 3-5 stereocenters derived from the phenyl carbons.

The Diels–Alder reaction of benzenes remains a significant synthetic challenge, owing to their highly stabilized aromatic cores. In this work, the dearomatization agent {WTp(NO)(PMe₃)} is used to promote Diels–Alder reactions of dihapto-coordinated (η²) benzenes with alkynes. The resulting η²-barrelene complexes can be oxidized to liberate intact barrelenes. Alternatively, mild pyrolysis leads to the extraction of the corresponding tungsten-acetylene complex and concomitant formation of new arenes possessing substituents originating from the acetylene dienophiles.

We report the synthesis of Rh–Sb complexes using high valent Sb ligands, Q₃SbCl₂ (1, Q = 8-quinolinyl) and Q₃SbF₂ (2), from the low valent Rh precursor [(CO)₂Rh(μ-Cl)]₂ to afford the complexes [(κ⁴-Q₃SbCl)Rh(CO)Cl][(CO)₂RhCl₂] (3) and (κ⁴-Q₃SbF₂)Rh(CO)Cl (4), respectively. The reaction of 1 with [(CO)₂Rh(μ-Cl)]₂ results in the transfer of chloride from Sb to Rh to give the ion pair 3 with a Rh–Sb bond for the cation that, according to computational analysis, has some covalent character. Replacing Sb–Cl with Sb–F bonds (i.e., compound 2) inhibited halide transfer and allowed formation of 4 with a Rh→Sb interaction that has more Z-type character than the Rh–Sb bond for complex 3. Molecular orbital and localized orbital bonding analyses are consistent with the proposed Rh→Sb interaction of 4 being more Z-type in character.