An Imidazole-functionalized Dioxovanadium Complex with the Highly Selective Oxidation of Sulfides

A novel imidazole-functionalized dioxovanadium complex [V2O2（C2O4）（aIM）4] （aIM =1-allylimidazole） was synthesized by the reaction of VO（acac）2 with 1-allylimidazole and fully characterized by single-crystal X-ray diffraction （SCXRD）,powder X-ray diffraction （PXRD）,X-ray photoelectron spectroscopy （XPS）,Fourier transform infrared spectroscopy （FT-IR） and elemental analyses.Interestingly,the oxalate was in-situ generated from the acetylacetone anion of VO（acac）2 and further coordinated with the vanadium cation and finally complex 1 was achieved.The crystal of complex 1 belongs to the monoclinic system,space group P21/n with a =10.7922（9）,b =10.6296（8）,c =13.2936（11） （A）,μ =0.677 mm^-1,Mr =686.48,V =1516.9（2） A^3,Z =2,Dc =1.503 g/cm^3,F（000） =708,R =0.0543,and wR =0.1517 for 2459 observed reflections with Ⅰ 〉 2σ（Ⅰ）.Notably,complex 1 is further used as catalyst in the oxidation of sulfides using H2O2 as the oxidant and exhibits excellent catalytic performance （conv.up to 95.6%,sele.up to 98.9%）.

Four unprecedented V_(14)clusters as highly efficient heterogeneous catalyst for CO_(2)fixation with epoxides and oxidation of sulfides

Chemical fixation of carbon dioxide(CO_(2))is an energy-saving method for alleviating the greenhouse gas emissions,whereas it persists a challenge posed by the demand for efficient catalysts.Herein,four unprecedented examples of tetradecanuclear vanadium clusters,namely,[(C_(2)H_(8)N_(2))6(CH_(3)O)8(CH_(3)OH)_(2)V_(10)^(Ⅳ)V_(4)ⅤO_(26)](V_(14)-1),[(C_(3)H_(10)N_(2))_(6)(CH_(3)O)_(8)(CH_(3)OH)_(2)V_(10)^(Ⅳ)V_(4)ⅤO_(26)](V14^(-2)),[(C_(6)H_(14)N_(2))6(CH_(3)O)8(CH_(3)OH)_(2)V_(10)^(Ⅳ)V_(4)ⅤO_(26)]·5H_(2)O(V14^(-3))and[(C_(4)H_(12)N_(2)O)_(4)(C_(4)H_(11)N_(2)O)_(2)(CH_(3)O)_(2)V_(10)^(Ⅳ)V_(4)ⅤO_(28)]·6H_(2)O(V_(14)-4),have been triumphantly designed and constructed under solvothermal conditions.Among them,compounds V_(14)-1–4 are the first cases of tetradecanuclear vanadium clusters without the introduction of inorganic acid radical ions.Two main units[V_(10)^(Ⅳ)V_(4)ⅤO_(26)]8+and[V10ⅣV4ⅤO28]4+represent brand-new configurations of tetradecanuclear vanadium clusters.Given the fact that the presence of V^(Ⅳ)/V^(Ⅴ)can potentially facilitate electron transfer and consequently expedite catalytic reactions,we explored the catalytic activities of these compounds.Remarkably,V_(14)-1 was further used as a heterogeneous catalyst in the CO_(2)fixation into cyclic carbonates under milder conditions(60℃,0.5 MPa)and exhibited higher catalytic activity.Also,the experimental results indicated that V_(14)-1 could efficiently catalyze the sulfoxidation,which could fully convert most sulfides within 40 min at room temperature.Moreover,as a stable heterogeneous catalyst employed in CO_(2)fixation with epoxides and oxidation of sulfides,V_(14)-1 could be consecutively used multiple cycles without losing its catalytic activity.

Extending aromatic acids on TiO_(2)for cooperative photocatalysis with triethylamine:Violet light-induced selective aerobic oxidation of sulfides

Designing visible light photocatalysts with a metal oxide semiconductor as the starting material could expand a new horizon for the conversion and storage of solar energy.Here,the benchmark photocatalyst TiO_(2) was used to pursue this goal by anchoring aromatic acids.Extending the aromatic acid was strategically deployed to design TiO_(2) complexes with violet light-induced selective aerobic oxidation of sulfide as the probe reaction.With benzoic acid(BA)as the initial molecule,horizontally extending one or two benzene rings furnishes 2-naphthoic acid(2-NA)and 2-anthracene acid(2-AA).Moreover,triethylamine(TEA),an electron transfer mediator,was introduced to maintain the integrity of the anchored aromatic acids.Notably,there was a direct correlation between theπ-conjugation of aromatic acid ligand and the selective aerobic oxidation of sulfides.Among the three aromatic acids,2-AA delivered the best result over TiO_(2) due to the most extensiveπ-conjugated system.Ultimately,violet light-induced selective aerobic oxidation of sulfides into corresponding sulfoxides was conveniently realized by cooperative photocatalysis of 2-AA-TiO_(2) with 10 mol%of TEA.This work affords an extending strategy for designing the next-generation ligands for semiconductors to expand visible light-induced selective reactions.

Decavanadate-based Transition Metal Hybrids as Bifunctional Catalysts for Sulfide Oxidation and C-C Bond Construction

The development of bifunctional catalysts has drawn much attention in realizing efficient and feasible catalytic systems to meet the diverse dema nd of pote ntial industrial applications.Desig n of stable and powerful bifun ctional catalysts for various catalysis systems is highly desirable yet largely unmet.Here,three kinds of decavanadate-based transition metal hybrids(DTMH)(i.e.,Co-DTMH,Ni-DTMH and Ag-DTMH)have been successfully synthesized through a pH tuning strategy and further characterized.Specifically,the rare M05N six-coordinated transition metal coordination modes have been detected in Co-DTMH and Ni-DTMH,while Ag atoms in Ag-DTMH exhibited three-and five-coordinated geometries with the tuning of specially selected imidazole ligands.Thus-obtained clusters can serve as powerful bifunctional catalysts for both sulfide oxidation and C-C bond construction.Remarkably,Ag-DTMH dem on st rated excellent heteroge ne ous bifunctional catalytic properties in the selective oxidati on of sulfides and construction of C-C bond(yields up to 99%),which enable successful recycling for three cycles with remained catalytic activities and structure stability.The newly designed decavanadate-based transition metal hybrids with bifunctional property hold high promise in the practical applications like continuous catalysis or flow bed reactions.