Reactivity Of Metallapentalenes

Organometallic chemistry,which is the subject that studies the synthesis,structures,reactivity and applications of compounds which contains metal-carbon bond is one of the frontier research area.Metallaaromatic chemistry which attracts considerably attentions since the propose in 1979 is an important branch of organometallic chemistry.Since 2013,our group reported a series of metallapentalynes and metallapentalenes with novel planar Craig-type Mobius aromaticity and unique properties which indicates the extensive applications.In this dissertation,the reactivity of metallapentalenes are studied,resulted in the construction of a number of novel structures and the applications in catalytic reaction.The dissertation consists of the following six chapters:In chapter 1,the general conception and criteria of aromaticity were briefly introduced.In addition,the reactivity of metal carbenes,metallacyclopropane and metallacyclopropene which closely related to the main objective of this dissertation were also summarized.In chapter 2,the reactions of rhodapentalene with isonitriles were investigated,led to the formations of a series of rhodaindene.Mechanism studies indicated that the reaction started with the nucleophilic attack of isonitrile to the carbene carbon of rhodapentalene,instead of migratory insertion pathway.This provided the first direct evidence in the mechanism of the generate of ketenimine by the reactions of metal carben with isonitriles.Further studies showed that rhodaindenes bearing electron-donating group could convert into indenimine motif which were expected to be a catalytic reaction in multisubstituted indenimine synthesis.In chapter 3,the reactivity of rhodapentalene was investigated and a catalytic reaction based on the reactivity was designed.The catalytic reaction led to the formation of multisubstituted tetraphenyl phosphonium salt by a one pot cascade cyclization catalyzed by RhCl(PPh3)3.In addition,the redox isomerization of allylic alcohols catalyzed by rhodapentalene was performed,providing a perspective of application of metallaaromatics in catalytic chemistry.In chapter 4,the reactions of rhodapentalerie with oxidants were investigated,led to the formation of oxygen atom insertion products.Further studies found that rhodapentalene could react with various nucleophilic reagents containing heteroatom,all led to the formation of heteroatom insertion products.These reactions indicated the nature of eletrophilicity in the carbene carbon of rhodapentalene.In chapter 5,the reactions of metallacyclopropene in osmapentalene derivate with alkynes with the assist oxidants were investigated.A series of novel osmacycles were constructed with the help of the oxidation of pyridine-N-oxide and the nucleophilicity of metallacyclopropene.1)The alkyne bond could be oxidized into carboxylic acid and coordinated to the metal atom in the reaction of the metallacyclopropene with dimethyl acetylenedicarboxylate.2)Ring expansion reactions occurred when the metallacyclopropene reacted with terminal alkyne,leding to the formation of metallapentalyne derivatives.3)In the reaction of the metallacyclopropene with propargylic alcohols,a metallacyclobutadiene and a metallafuran ring were constructed at one step reaction.Theoretical calculation suggested that the metallafuran ring in the product was aromatic and the original osmapentalene ring converted into nonaromatic.Further studies showed that the nonaromatic ring could convert into aromatic osmapentalene ring by the oxidation of PhI(OAc)2.In chapter 6,the summary of this dissertation was concluded and the prospect of this research was also presented.