Rainfall was witnessed for the first time at the highest area of the Greenland Ice Sheet on 14 August,2021.The thermodynamic mechanisms supporting the rainfall are revealed by ERA5 reanalysis,in-situ and satellite dat...Rainfall was witnessed for the first time at the highest area of the Greenland Ice Sheet on 14 August,2021.The thermodynamic mechanisms supporting the rainfall are revealed by ERA5 reanalysis,in-situ and satellite data.We find that a strong southward intrusion of the polar vortex favored the maintenance of a deep cyclone over Baffin Island and an amplification of anticyclonic circulation over the southeastern ice sheet,which pumped warm and moist air toward Greenland from anomalously warm waters south of Greenland.Across a wide swath of the ice sheet,atmospheric uplift maintained above-melting and rainfall conditions via condensation and enhanced downward infrared irradiance.Without the low-level liquid clouds,the spatial extent and duration of the rainfall would have been smaller.Over the ice sheet topographic summit,the air temperature from the ground to 250 hPa level was~2℃higher than the previous record set on 12 July,2012.Such events may occur more frequently with the decreased temperature contrast between the Arctic and the mid-latitude regions that drives highly amplified jet streams.Thus,this extreme event serves as a harbinger of a more likely wet surface condition across all elevations of the ice sheet.展开更多
The metal-carbon bonds in metal-carboranyl and metal-carboryne complexes behave very differently from those in classical organometallic complexes. The unique electronic and steric properties of ico-sahedral carboranyl...The metal-carbon bonds in metal-carboranyl and metal-carboryne complexes behave very differently from those in classical organometallic complexes. The unique electronic and steric properties of ico-sahedral carboranyl moiety make the M-C bond in metal-carboranyl complexes inert toward unsaturated molecules, and on the other hand, the sterically demanding carborane cage can induce unexpected C-C coupling reactions. The M-C bonds in metal-carboryne complexes are, however, active toward various kinds of unsaturated molecules and the reactivity patterns are dependent upon the electronic configurations of the metal ions. This account provides an overview of our recent work in this area.展开更多
Transmetalation of carborane-fused zirconacycles to Cu（II） induces the C-C coupling reaction to form four-membered rings. This serves as a new efficient and general methodology for the generation of a series of carb...Transmetalation of carborane-fused zirconacycles to Cu（II） induces the C-C coupling reaction to form four-membered rings. This serves as a new efficient and general methodology for the generation of a series of carborane-fused cyclobutenes and cyclobutanes. A reaction mechanism involving transmetalation to Cu（II） and reductive elimination is proposed.展开更多
As one of the most important five-member heterocyclic aromatic rings, pyrrole is widely distributed in numerous natural products and pharmaceutical agents. Asymmetric dearomatization of pyrroles is very attractive in ...As one of the most important five-member heterocyclic aromatic rings, pyrrole is widely distributed in numerous natural products and pharmaceutical agents. Asymmetric dearomatization of pyrroles is very attractive in organic synthesis given the fact that highly functionalized chira pyrrolines and pyrrolidines could be easily accessed from the readily available pyrroles. However, the reported asymmetric dearomatization reactions of pyrroles are limited to transition-metal-catalyzed [4＋3] cycloaddition and hydrogenation reactions.展开更多
Carboranes are a class of boron hydride clusters in which one or more of the BH vertices are replaced by CH units.Unlike small boranes, carboranes are kinetically and thermodynamically very stable as well as relativel...Carboranes are a class of boron hydride clusters in which one or more of the BH vertices are replaced by CH units.Unlike small boranes, carboranes are kinetically and thermodynamically very stable as well as relatively chemically inert, which are often called three-dimensional relatives of benzenes. They are finding many applications in medicine as boron neutron capture therapy（BNCT） agents, in nanomaterials/supramolecular design as building blocks, and as ligands for transition metals [1]. However, their unique structures make derivatization difficult, which limits their application scope.展开更多
基金supported by the National Key Research&Development Program of China (Grant no.2018YFC1406104)conducted by Geological Survey of Denmark and Greenland (GEUS)under support from the Danish Ministry of Climate,Energy and Utilities via The Programme for Monitoring of the Greenland Ice Sheet (PROMICE)the INTAROS project under the European Union's Horizon 2020 Research and Innovation Program under grant agreement no.727890。
文摘Rainfall was witnessed for the first time at the highest area of the Greenland Ice Sheet on 14 August,2021.The thermodynamic mechanisms supporting the rainfall are revealed by ERA5 reanalysis,in-situ and satellite data.We find that a strong southward intrusion of the polar vortex favored the maintenance of a deep cyclone over Baffin Island and an amplification of anticyclonic circulation over the southeastern ice sheet,which pumped warm and moist air toward Greenland from anomalously warm waters south of Greenland.Across a wide swath of the ice sheet,atmospheric uplift maintained above-melting and rainfall conditions via condensation and enhanced downward infrared irradiance.Without the low-level liquid clouds,the spatial extent and duration of the rainfall would have been smaller.Over the ice sheet topographic summit,the air temperature from the ground to 250 hPa level was~2℃higher than the previous record set on 12 July,2012.Such events may occur more frequently with the decreased temperature contrast between the Arctic and the mid-latitude regions that drives highly amplified jet streams.Thus,this extreme event serves as a harbinger of a more likely wet surface condition across all elevations of the ice sheet.
基金Supported by the Research Grants Council of the Hong Kong Special Administration Region (Grant No. 404108)
文摘The metal-carbon bonds in metal-carboranyl and metal-carboryne complexes behave very differently from those in classical organometallic complexes. The unique electronic and steric properties of ico-sahedral carboranyl moiety make the M-C bond in metal-carboranyl complexes inert toward unsaturated molecules, and on the other hand, the sterically demanding carborane cage can induce unexpected C-C coupling reactions. The M-C bonds in metal-carboryne complexes are, however, active toward various kinds of unsaturated molecules and the reactivity patterns are dependent upon the electronic configurations of the metal ions. This account provides an overview of our recent work in this area.
基金supported by the Research Grants Council of the Hong Kong Special Administration Region (404011)the National Natural Science Foundation of China (21372245 to QIU ZaoZao)
文摘Transmetalation of carborane-fused zirconacycles to Cu（II） induces the C-C coupling reaction to form four-membered rings. This serves as a new efficient and general methodology for the generation of a series of carborane-fused cyclobutenes and cyclobutanes. A reaction mechanism involving transmetalation to Cu（II） and reductive elimination is proposed.
文摘As one of the most important five-member heterocyclic aromatic rings, pyrrole is widely distributed in numerous natural products and pharmaceutical agents. Asymmetric dearomatization of pyrroles is very attractive in organic synthesis given the fact that highly functionalized chira pyrrolines and pyrrolidines could be easily accessed from the readily available pyrroles. However, the reported asymmetric dearomatization reactions of pyrroles are limited to transition-metal-catalyzed [4＋3] cycloaddition and hydrogenation reactions.
文摘Carboranes are a class of boron hydride clusters in which one or more of the BH vertices are replaced by CH units.Unlike small boranes, carboranes are kinetically and thermodynamically very stable as well as relatively chemically inert, which are often called three-dimensional relatives of benzenes. They are finding many applications in medicine as boron neutron capture therapy（BNCT） agents, in nanomaterials/supramolecular design as building blocks, and as ligands for transition metals [1]. However, their unique structures make derivatization difficult, which limits their application scope.
