Sonochemical Synthesis of Small Boron Oxide Nanoparticles

The synthesis of small boron oxide nanoparticles (NPs) is reported. A sonochemical approach in the presence of a capping agent was employed to produce approximately 4–5-nm-sized B₂O₃ NPs, including the ¹⁰B isotopically enriched form. The morphology and composition of the NPs were established using transmission electron microscopy and diffraction, respectively. X-ray photoelectron and Fourier transform infrared spectroscopies provided information about surface functionalization of the B₂O₃ NPs, which can be further modified through a facile, one-step ligand-exchange process. The toxicity of the synthesized NPs was investigated in Chinese hamster ovarian cells, indicating that these systems were nontoxic up to 1.7 mM concentrations

Metal-Free Peralkylation of the <i>closo</i>-Hexaborate Anion

The synthesis of fully alkylated <i>closo</i>-hexaborate dianions is reported. The reaction of [NBu₄]­[B₆H₆H^<i>fac</i>], benzyl bromide, and triethylamine under microwave heating conditions affords persubstituted [NBu₄]­[B₆(CH₂Ar)₆H^<i>fac</i>] (Ar = C₆H₅, 4–Br-C₆H₄), which have been isolated and characterized by NMR spectroscopy, mass spectrometry, single-crystal X-ray diffraction, and other spectroscopic techniques. Electrochemical studies of these clusters reveal an irreversible one-electron oxidation, likely indicating degradative cage rupture. The observed metal-free alkylation is proposed to proceed as a consequence of the pronounced <i>nucleophilic</i> character of the hexaborate anion. This work represents the first example of a perfunctionalized hexaborate cluster featuring B–C bonds

Metal-Free Peralkylation of the <i>closo</i>-Hexaborate Anion

The synthesis of fully alkylated <i>closo</i>-hexaborate dianions is reported. The reaction of [NBu₄]­[B₆H₆H^<i>fac</i>], benzyl bromide, and triethylamine under microwave heating conditions affords persubstituted [NBu₄]­[B₆(CH₂Ar)₆H^<i>fac</i>] (Ar = C₆H₅, 4–Br-C₆H₄), which have been isolated and characterized by NMR spectroscopy, mass spectrometry, single-crystal X-ray diffraction, and other spectroscopic techniques. Electrochemical studies of these clusters reveal an irreversible one-electron oxidation, likely indicating degradative cage rupture. The observed metal-free alkylation is proposed to proceed as a consequence of the pronounced <i>nucleophilic</i> character of the hexaborate anion. This work represents the first example of a perfunctionalized hexaborate cluster featuring B–C bonds

Metal-Free Peralkylation of the <i>closo</i>-Hexaborate Anion

The synthesis of fully alkylated <i>closo</i>-hexaborate dianions is reported. The reaction of [NBu₄]­[B₆H₆H^<i>fac</i>], benzyl bromide, and triethylamine under microwave heating conditions affords persubstituted [NBu₄]­[B₆(CH₂Ar)₆H^<i>fac</i>] (Ar = C₆H₅, 4–Br-C₆H₄), which have been isolated and characterized by NMR spectroscopy, mass spectrometry, single-crystal X-ray diffraction, and other spectroscopic techniques. Electrochemical studies of these clusters reveal an irreversible one-electron oxidation, likely indicating degradative cage rupture. The observed metal-free alkylation is proposed to proceed as a consequence of the pronounced <i>nucleophilic</i> character of the hexaborate anion. This work represents the first example of a perfunctionalized hexaborate cluster featuring B–C bonds

Metal-Free Peralkylation of the <i>closo</i>-Hexaborate Anion

The synthesis of fully alkylated <i>closo</i>-hexaborate dianions is reported. The reaction of [NBu₄]­[B₆H₆H^<i>fac</i>], benzyl bromide, and triethylamine under microwave heating conditions affords persubstituted [NBu₄]­[B₆(CH₂Ar)₆H^<i>fac</i>] (Ar = C₆H₅, 4–Br-C₆H₄), which have been isolated and characterized by NMR spectroscopy, mass spectrometry, single-crystal X-ray diffraction, and other spectroscopic techniques. Electrochemical studies of these clusters reveal an irreversible one-electron oxidation, likely indicating degradative cage rupture. The observed metal-free alkylation is proposed to proceed as a consequence of the pronounced <i>nucleophilic</i> character of the hexaborate anion. This work represents the first example of a perfunctionalized hexaborate cluster featuring B–C bonds

Blue Phosphorescent Zwitterionic Iridium(III) Complexes Featuring Weakly Coordinating <i>nido</i>-Carborane-Based Ligands

We report the development of a new class of phosphorescent zwitterionic <i>bis</i>(heteroleptic) Ir­(III) compounds containing pyridyl ligands with weakly coordinating <i>nido</i>-carboranyl substituents. Treatment of phenylpyridine-based Ir­(III) precursors with <i>C</i>-substituted <i>ortho</i>-carboranyl­pyridines in 2-ethoxyethanol results in a facile carborane deboronation and the formation of robust and highly luminescent metal complexes. The resulting <i>nido</i>-carboranyl fragments associate with the cationic Ir­(III) center through primarily electrostatic interactions. These compounds phosphoresce at blue wavelengths (450–470 nm) both in a poly­(methyl methacrylate) (PMMA) matrix and in solution at 77 K. These complexes display structural stability at temperatures beyond 300 °C and quantum yields greater than 40%. Importantly, the observed quantum yields correspond to a dramatic 10-fold enhancement over the previously reported Ir­(III) congeners featuring carboranyl-containing ligands in which the boron cluster is covalently attached to the metal. Ultimately, this work suggests that the use of a ligand framework containing a weakly coordinating anionic component can provide a new avenue for designing efficient Ir­(III)-based phosphorescent emitters

Buchwald-Hartwig Amination Using Pd(I) Dimer Precatalysts Supported by Biaryl Phosphine Ligands

We report the synthesis of air-stable Pd(I) dimer complexes featuring biaryl phosphine ligands. Catalytic experiments suggest that these complexes are comptent precatalysts that can mediate cross-coupling amination reactions between aryl halide electrophiles with both aliphatic and aromatic amine nucleophiles. This work represents an expansion of the air-stable precatalyst toolbox for Pd-catalyzed cross-coupling transformations