Hypercoordinated Carbon-Centered Polymetallic Compounds:Synthesis,Reactivity And Applications

Organometallic clusters with hypercoordinated carbon centers（hypercarbons）and an uncommon[C-M_n]（n=2-6）multicenter bonding constitute a class of unique compounds,which are recognized as key intermediates in homogeneous multimetallic catalytic systems or metal surface catalysis.In-depth studies of hypercarbon-centered polymetallic compounds not only supply fundamental understanding on polymetal-involved organometallic transformations,but also foster the extensive application of those compounds in an interdisciplinary field of organometallic,catalytic and bioinorganic chemistry.In this thesis,we have developed an efficient synthetic method for hypercarbon-centered polymetallic compounds under mild conditions based on the Baldwin rule.Detailed reaction kinetics were carried out to explore the nature of carbon-polymetal bonding and how the degree of metalation influences bond activation and rupture.The comprehension of bonding in organometallic clusters inspires their applications in anti-tumor prodrugs and photocatalysts.The major contents include the following items:1.Based on in situ cyclization reactions and controllable polymetalation,aryl（sp²）and benzyl（sp³）hypercoordinated gold clusters with different nuclearity numbers were prepared.The penta-aurated indolium with dual hyperconjugation shows better hyperconjugative aromaticity than the tetra-aurated indolium containing only one hyperconjugation site,finally leading to a higher protodeauration activity.In addition,the stepwise polymetalation around a benzyl carbon from gem-diaurated to tetra-aurated was studied by kinetic monitoring and theoretical calculations.The activation of ipso-C-Si bond was promoted by the synergistic electronic effect of polymetalation.2.We revealed a consecutive decomposition pathway of hypercarbon-centered gold clusters upon thiol coordination.The synergistic mechanism was verified by kinetic studies.Such unique gold（I）release process triggered by glutathione facilitates the application as a metal cluster prodrug for bladder tumor treatment.Both in vitro and in vivo studies substantiate that the hypercarbon-centered gold clusters kinetically release active metal ions to inhibit enzymes and efficiently induce pro-oxidant response,eventually causing ferroptosis of cancer cells.3.We synthesized a series of close-packed Ag₁₃clusters surrounded by six hypercoordinated aryls via an one-pot synthetic method.The Ag₁₃clusters exhibit high molar absorption coefficients in visible region,and long-lived phosphorescent emission with considerable quantum yields.The triplet excited state can be ascribed to metal-metal to ligand charge transfer within the aryl-hypercoordinated polymetal skeletons.The Ag₁₃clusters also show quasi-reversible redox properties.Quenching studies between the excited Ag₁₃clusters and a series of oxidants and reductants via intermolecular electron transfer demonstrate its capability to serve as a novel cluster-based photocatalyst.In summary,in this thesis we developed an efficient synthetic method to in situ synthesize a series of hypercarbon-centered polymetallic compounds.With sophisticated studies of reaction kinetics on the aryl（sp²）or benzyl（sp³）centered carbon-polymetal complexes,we have found that the polymetalation could influence the reactivity of hypercoordinated organics in the processes of cooperative bond activation or synergistic multicenter bond dissociation.Moreover,we have also exerted the application of those compounds in organometallic cluster-based prodrugs and photocatalysts.Our studies will deepen the comprehension of bonding and reactivity nature of hypercarbon-centered polymetallic compounds and promote their applications in homogeneous and heterogeneous catalysis,bio-inorganic medicine,optical function materials and other fields.