Application Of Four-Membered Heterocyclic Biradicaloid Dicarbondiphosphide In The Field Of Small Molecule Activation

Currently,activation of small molecules is a hot topic in chemistry.For a long time,it was believed that only amphiphilic transition metal?TM?coordination compounds can activate small molecules,because they have both electron-occupied and empty d-orbits that can make strong bonds fracture to activate small molecules.However,some recent studies have demonstrated that biradicaloids with main-group elements also have similar activation functions as TM coordination compounds.These free radicals have unbonded electrons or some active?electrons.Meanwhile,some main-group elements,having the same d orbits as TM,are used to receive electrons of?orbits in the chemical bonds of small molecules,and inclined to trigger fracture and addition reaction of small molecules.Many biradicaloids not only react with such small molecules as H₂,NH₃,CO₂,etc.,but also can be used as high-performance organic catalysts,opening up new fields for activation of small molecules.In this thesis,P₂C₂four-membered heterocyclic biradicaloid was used for the oxidative addition reaction with 12 small molecules such as water,malonic nitrile?P-acetonitrile aniline,methyl iodide and ethyl iodide,and the mechanism of activating E-H?E=C,N and O?bond and R-X?R=alkane,X=halogen?bond was studied.A brief introduction of each chapter of the thesis is as follows.The first chapter is an overview of the chemical properties of biradicaloids,different types of four-membered heterocyclic biradicaloid and their application in activation of small molecules.1.Study and development of four-membered heterocyclic biradicaloid;2.Application of four-membered heterocyclic biradicaloids in activation of small molecules and relevant discussions;In Chapter 2,we separated a type of NHC?N-heterocyclic carbene?in previous efforts to stabilize 6?electron L??C₂P₂??L(L=NHC=1,3-di?2,6-diisopropylphenylimino N-heterocyclic carbene?,four-membered heterocyclic biradicaloid compound 1 to realize oxidative addition with small molecules.When the substrate approached compound 1 through substrate induction,inter-molecular electronic interaction led to fluctuation of?electron in compound 1,making the two P atoms equivalent in ground state no longer equivalent and thereby showing nucleophilicity and electrophilicity centering on P atoms.In the biradicaloid compound 1 containing stable N-heterocyclic carbene,it interacted with a small molecule substrate with a E-H bond?E=C,N,O?of polarity to generate a series of asymmetric 1,3-diphosphates skeleton(including P-C?2-2?,P-N?2-6 and 2-7?and P-O bond?2-8b,2-8c and 2-9?.Besides,1,3-diphosphates salt was also obtained through weak coordination with?[?CN?₂CH]^–?2-3?and[?Ph OH?₂Ph O]^–?2-10??.Nuclear magnetic resonance?NMR?spectrum,diffraction of x-rays,UV-visible spectroscopy,and infrared spectroscopy?IR?were used for characterization,while NMR and single crystal data indicated that small molecules will react with compound 1 to produce cis-trans isomers,and the reaction mechanism were studied based on density functional theory?DFT?calculation.In Chapter 3,we used compound 1 to realize oxidative addition reaction with small molecules containing R-X bond?R refers to alkyl while X refers to halogen I atom?.Compound1 reacted with Me,Et I,1-iodo-2-methylpropane and 2-iodo-2-methylpropane and obtained corresponding compounds 3-3a?3-3b?3-3c and 3-4 respectively,which lead to fracture of R-X bond,R being added to one of the P atoms on the four-membered rings in Compound 1,forming R?LPC?₂⁺cation and X^-negion.Characterization data,including NMR,infrared,ultraviolet and monocrystal,were used to analyze the chemical properties of the products and theoretically study the electron transfer of the transient state in the reaction through mechanical calculation.