Cooperative Rare-Earth/Lithium-Mediated Conversion of White Phosphorus

The rare-earth/lithium cooperative effect on functionalization of white phosphorus has been investigated. The reaction of diazabutadiene-supported yttrium hydride chelated a LiPPh₂ molecule (LY ⋅ THF)₂ (μ-H)₂ [μ-PPh₂ (Li)] (1, L=N,N'-di(2,6-diisopropylphenyl)-1,4-diazabutadiene) with P₄ gave two novel mixed Y/Li multinuclear polyphosphorus complexes (LY ⋅ THF)₂ [cyclo-P₃ ]Li(THF)₃ (2) and [Li(THF)₄ ]⁺ [(LY ⋅ THF)₃ (norborane-P₇ )Li(THF)]^- (3), accompanied with the elimination of diphosphorus compound Ph₂ PPPh₂ (4) and H₂ . However, the comparative reaction of yttrium hydride (LY ⋅ THF)₂ (μ-H)₂ with P₄ afforded a trinuclear yttrium pyramid-P₄ complex (LY ⋅ THF)₃ (μ₃ -P(PH)₃ ) (5). Further investigations show that 5 cannot continuously react with LiPPh₂ to form 2 and 3, and LiPPh₂ reacted with P₄ to form a Zintl-P₇ lithium complex (TMEDA⋅Li)₃ (Zintl-P₇ ) (6) and 4. These results indicated that the cooperation of Y/Li for activation of P₄ is a key for the formation of 2 and 3. All new compounds have been characterized by NMR spectroscopy and single-crystal X-ray diffraction studies.

Cationic Zn-Porphyrin Polymer Coated onto CNTs as a Cooperative Catalyst for the Synthesis of Cyclic Carbonates

The development of solid catalysts containing multiple active sites that work cooperatively is very attractive for biomimetic catalysis. Herein, we report the synthesis of bifunctional catalysts by supporting cationic porphyrin-based polymers on carbon nanotubes (CNTs) using the direct reaction of 5,10,15,20-tetrakis(4-pyridyl)porphyrin zinc(II), di(1H-imidazol-1-yl)methane, and 1,4-bis(bromomethyl)benzene in the presence of CNTs. The bifunctional catalysts could efficiently catalyze the cycloaddition reaction of epoxides and CO₂ under solvent-free conditions with porphyrin zinc(II) as the Lewis acid site and a bromine anion as a nucleophilic agent working in a cooperative way. Furthermore, a relative amount of porphyrin zinc(II) and quaternary ammonium bromide could be facilely adjusted for facilitating cooperative behavior. The bifunctional catalyst with a TOF up to 2602 h^-1 is much more active than the corresponding homogeneous counterpart and is one of the most active heterogeneous catalysts ever reported under cocatalyst-free conditions. The high activity is mainly attributed to the enhanced cooperation effect of the bifunctional catalyst. With a wide substrate scope, the bifunctional catalyst could be stably recycled. This work demonstrates a new approach for the generation of a cooperative activation effect for solid catalysts.

Homolytic Cleavage of a B-B Bond by the Cooperative Catalysis of Two Lewis Bases: Computational Design and Experimental Verification

Density functional theory (DFT) investigations revealed that 4-cyanopyridine was capable of homolytically cleaving the B-B σ bond of diborane via the cooperative coordination to the two boron atoms of the diborane to generate pyridine boryl radicals. Our experimental verification provides supportive evidence for this new B-B activation mode. With this novel activation strategy, we have experimentally realized the catalytic reduction of azo-compounds to hydrazine derivatives, deoxygenation of sulfoxides to sulfides, and reduction of quinones with B2 (pin)2 at mild conditions.