Synthesis Of Boron Compounds With Boron Atom π Bond Structural Unit

The main group carbonyl analogues is an important research area in inorganic synthesis,and the derivatives containing B=E（E=S,Se,Te）group are also the focus of inorganic chemistry in recent years.C-O double bond is widely used as organic basic functional group in conversion reactions.The derivatives containing C=E group have been existed,although their applications are less abundant than C=O derivatives.Boron is not easy to form compounds containing B=E double bond compared with a great deal of 16 group elements C=E derivatives.In particular,the monomeric oxoborane is very difficult to capture,usually only detected in the gas phase,low temperature matrix or chemical capture concentration,and few synthetic samples are found for the moment.The aim of this master’s work is devoted to synthesize oxoborane and thioxoborane with unsaturated bond by using ligand dpp-bian.At the same time,it is hoped that the ligandβ-diketiminato will be used to synthesize monomic boron derivatives stabilized byβ-diketiminate ligand.The main achievements of this master’s research work are listed below:1.Threeα-diimine boron derivatives 2,3 and 4 were obtained by reacting BBr₃ with ligand dpp-bian and reduced ligand Na⁺[dpp-bian]^-,respectively.The synthesis of compounds 2 and4 further proves that the ligand dpp-bian can be either as a neutral chelating ligand or reduced to anionic ligand by metal.In the structure of 2,boron atom is a four-coordinate mode,using sp³ hybrid,the two bromine atoms are in the upper and lower plane of the five-membered boron heterocyclic plane.By contrast,the boron atom in compound 4 is a three-coordinate mode,using sp² hybrid,the bromine atom and the five-membered boron heterocycle are co-plane.The high yield synthesis of compounds 2 and 4 provides a basis for further study of unsaturated boron compounds.2.Using dpp-bian boron derivative 3 to hydrolyze in the presence of NHC,a new example of oxoborane anion 5 stabilized by imidazolium cation is obtained,in which the anion and canion are interrelated by C-H…O=B hydrogen bond.What’s more,the central boron atom in 3 adopts a trigonal planar geometry,the average B-O bond length is 1.291A,which is in the range of boron-oxygen double bond length reported in the literatures.Excessive CS₂ reaction with compound 5 resulted in the ionic thioxoborane 6.Different from oxoborane 5,there is no hydrogen bond interaction between the terminal B=S and imidazolium cation.Successful preparation of thioxoborane anion 6 further enrich B=S double bond compounds.3.In the presence of tetra（pentafluorophenyl）borate or AlCl₃,two new chloro-boron cations11 and 13 supported byβ-diketiminate ligand were obtained by usingβ-diketiminato and BCl₃reactions.At the same time,we also obtained compound 14 with C-H activation.The same configuration of cations in compounds 11 and 13,the central boron atom adopts a trigonal planar geometry.The successful preparation of compounds 11 and 13 provides a key raw material for the further study of the synthetic compounds of low valence boron carbene.4.A new compound 10 obtained by reaction betweenβ-diketiminato,BCl₃ and H₂O.Crystal structure shows that the Cl^-is above the six-membered ring,the oxygen atom and the six-membered boron heterocycle are co-plane.The successful synthesis of compound 10 provides raw materials for neutral oxoborane.We also obtained compound 12 with C-H activation.The anion and cation are associated with each other through a N-H…O hydrogen bond,and the N…O distance is 2.709A.The master’s work successfully prepared and characterized 10 novel N-heterocyclic boron derivatives.A new oxoborane anion and thioxoborane anion provide an important synthetic basis for the later exploration of compounds with B=E double bond,and also make a certain contribution to the synthesis of the main group carbonyl analogues.At the same time,the successful preparation of chloro-boron cations（11 and 13）and hydroxyl-boron cation 10supported byβ-diketiminate ligand have become a new research topic of boron unsaturated compounds and low valence boron chemistry.