Attaining the selective oxidation of isochroman into isochromanone in a molecular oxygen(O_(2))environment without any additives,via a heterogeneous oxidation process,is highly desirable and challenging work.Herein,we...Attaining the selective oxidation of isochroman into isochromanone in a molecular oxygen(O_(2))environment without any additives,via a heterogeneous oxidation process,is highly desirable and challenging work.Herein,we prepare two mixed-addendum polyoxometalate-based coordination polymers of the general formula[H_(x)M_(1-x)(i-PrIm)_(4)][H_(2)N(CH_(3))_(2)]_(4)[HPMo_(8)V_(6)O_(42)](M=Co 1,Ni,2;i-PrIm=1-isopropyl-1H-imidazole).Needing no additives,they can catalyze the selective oxidation of isochroman to isochromanone with O_(2)as an oxidant,with yields of 91.5%(1)and 46.8%(2),respectively.Mechanistic studies indicate that the excellent performance of catalyst 1 is attributed to the synergistic operation of[Co(i-Pr-Im)_(4))]complex and PMo_(8)V_(6)unit,and that the catalytic reaction is a radical pathway involving superoxide radicals.Additionally,the catalyst 1 can be recycled and reused at least four times with uncompromised performance.These results provide fundamental guidelines for designing efficient and multi-site heterogeneous catalysts for the selective oxidation of benzyl C(sp^(3))-H bonds by activating O_(2).展开更多
The synthesis of Ta-substituted polyoxometalates has always been an attractive but challenging goal.Three novel tantalum-containing 12-tungsto-2-phosphates were successfully prepared using the water bath method.The mo...The synthesis of Ta-substituted polyoxometalates has always been an attractive but challenging goal.Three novel tantalum-containing 12-tungsto-2-phosphates were successfully prepared using the water bath method.The monomer,K_(11)Li[P_(2)W_(12)(TaO_(2))_(6)O_(56)]·19H_(2)O(1),is composed of{P_(2)W_(12)}and 6{Ta(O_(2))}building blocks,similar to[P_(2)W_(12)(NbO_(2))_(6)O_(56)]^(12-).Monomer 1 polymerized to form two cis-trans dimers,K1_(3)Li_(6)H-cis-[P_(2)W_(12)Ta_(4)(TaO_(2))_(2)O_(59)]_(2)·61H_(2)O(2)and KNa_(3)Li_(4)H_(12)-trans-[P_(2)W_(12)Ta_(4)(TaO_(2))_(2)O_(59)]_(2)·37H_(2)O(3).Compounds 1-3 can serve as a structural motif to manufacture additional fascinating molecular clusters,promoting the advancement of POM chemistry.In contrast to[P_(2)W_(12)(NbO_(2))_(6)O_(56)]^(12-),compound 1 exhibits exceptional stability,evidenced by ESI-MS,IR,and NMR spectroscopy.In addition,2 and 3 exhibit high proton conductivity and superior water adsorption properties.展开更多
The visible-light-induced selective oxidation of ubiquitous C–H bonds into valuable C=O bonds under aerobic conditions is one of the most attractive approaches for the construction of carbonyl-containing molecules.In...The visible-light-induced selective oxidation of ubiquitous C–H bonds into valuable C=O bonds under aerobic conditions is one of the most attractive approaches for the construction of carbonyl-containing molecules.In this work,two transition metal-containing Nb/W mixed-addendum POMs dimers with the formula of K_(2)Na_(2)H_(5)[(Fe(H_(2)O)_(4))_(3)(P_(2)W_(15)Nb_(3)O_(62))_(2)]·24H_(2)O(POM[Fe])and K_(2)Na_(3)H_(4)[(Cr(H_(2)O)_(4))_(3)(P_(2)W_(15)Nb_(3)O_(62))_(2)]·32H_(2)O(POM[Cr])have been synthesized and characterized by various analytical and spectral techniques.POM[Fe]was proved to be an efficient photocatalyst for benzylic C–H oxidation under visible light and using oxygen as an oxidant to produce the corresponding carbonyl complex in good yields.A plausible mechanism involving superoxide radical was proposed for the catalytic reaction.POM[Fe]showed good reusability in the recycling experiments.IR spectroscopy and XRD analysis indicate that POM[Fe]can retain its integrity after catalysis.展开更多
基金financially supported by the National Natural Science Foundation of China(Nos.22171122 and 22201123)Liaoning Revitalization Talents Program(No.XLYC 2007130)+1 种基金Fundamental Research Project(No.LJ212410148038)of the Educational Department of Liaoning ProvinceTalent Scientific Research Fund of Liaoning Petrochemical University(No.2016XJJL–019)。
文摘Attaining the selective oxidation of isochroman into isochromanone in a molecular oxygen(O_(2))environment without any additives,via a heterogeneous oxidation process,is highly desirable and challenging work.Herein,we prepare two mixed-addendum polyoxometalate-based coordination polymers of the general formula[H_(x)M_(1-x)(i-PrIm)_(4)][H_(2)N(CH_(3))_(2)]_(4)[HPMo_(8)V_(6)O_(42)](M=Co 1,Ni,2;i-PrIm=1-isopropyl-1H-imidazole).Needing no additives,they can catalyze the selective oxidation of isochroman to isochromanone with O_(2)as an oxidant,with yields of 91.5%(1)and 46.8%(2),respectively.Mechanistic studies indicate that the excellent performance of catalyst 1 is attributed to the synergistic operation of[Co(i-Pr-Im)_(4))]complex and PMo_(8)V_(6)unit,and that the catalytic reaction is a radical pathway involving superoxide radicals.Additionally,the catalyst 1 can be recycled and reused at least four times with uncompromised performance.These results provide fundamental guidelines for designing efficient and multi-site heterogeneous catalysts for the selective oxidation of benzyl C(sp^(3))-H bonds by activating O_(2).
基金supported by the National Natural Science Foundation of China(Nos.22071044,21771054 and 22171071)。
文摘The synthesis of Ta-substituted polyoxometalates has always been an attractive but challenging goal.Three novel tantalum-containing 12-tungsto-2-phosphates were successfully prepared using the water bath method.The monomer,K_(11)Li[P_(2)W_(12)(TaO_(2))_(6)O_(56)]·19H_(2)O(1),is composed of{P_(2)W_(12)}and 6{Ta(O_(2))}building blocks,similar to[P_(2)W_(12)(NbO_(2))_(6)O_(56)]^(12-).Monomer 1 polymerized to form two cis-trans dimers,K1_(3)Li_(6)H-cis-[P_(2)W_(12)Ta_(4)(TaO_(2))_(2)O_(59)]_(2)·61H_(2)O(2)and KNa_(3)Li_(4)H_(12)-trans-[P_(2)W_(12)Ta_(4)(TaO_(2))_(2)O_(59)]_(2)·37H_(2)O(3).Compounds 1-3 can serve as a structural motif to manufacture additional fascinating molecular clusters,promoting the advancement of POM chemistry.In contrast to[P_(2)W_(12)(NbO_(2))_(6)O_(56)]^(12-),compound 1 exhibits exceptional stability,evidenced by ESI-MS,IR,and NMR spectroscopy.In addition,2 and 3 exhibit high proton conductivity and superior water adsorption properties.
基金supported by the National Natural Science Foundation of China(Nos.22171073.21971224 and U1804253)the Natural Science Foundation of Henan Province(No.202300410246).
文摘The visible-light-induced selective oxidation of ubiquitous C–H bonds into valuable C=O bonds under aerobic conditions is one of the most attractive approaches for the construction of carbonyl-containing molecules.In this work,two transition metal-containing Nb/W mixed-addendum POMs dimers with the formula of K_(2)Na_(2)H_(5)[(Fe(H_(2)O)_(4))_(3)(P_(2)W_(15)Nb_(3)O_(62))_(2)]·24H_(2)O(POM[Fe])and K_(2)Na_(3)H_(4)[(Cr(H_(2)O)_(4))_(3)(P_(2)W_(15)Nb_(3)O_(62))_(2)]·32H_(2)O(POM[Cr])have been synthesized and characterized by various analytical and spectral techniques.POM[Fe]was proved to be an efficient photocatalyst for benzylic C–H oxidation under visible light and using oxygen as an oxidant to produce the corresponding carbonyl complex in good yields.A plausible mechanism involving superoxide radical was proposed for the catalytic reaction.POM[Fe]showed good reusability in the recycling experiments.IR spectroscopy and XRD analysis indicate that POM[Fe]can retain its integrity after catalysis.
