Novel Transition Metal Complexes Based On Carboxylic Acid Ligand And Their Applications In Hydrogen Transfer Reactions

Coordination complexes have been received widespread attention because of their high activity,good selectivity and excellent stability.However,most of them are not cost effective and recoverability,which limit their development and application.Along with the development of“Green Chem.”,the main direction of catalysis is to develop sustainable,low-cost and environmentally catalysts.We are focusing on the coordination complexes based on the carboxylic acid ligand in order to use them as“Green catalyst”.In this paper,we describe the development of coordination complexes based on carboxylic acid ligand briefly,the overview of borrowing hydrogen and C-H activation reaction are included as well.We are focusing on the exploring coordination complexes based on carboxylic acid ligand,which can be used as efficient and recoverable catalyst in hydrogen transfer reaction.A new carboxylic acid complex Zn₂(BADA)(DIB)₂(2.4a)has been synthesized based on4-di(1H-imidazol-1-yl)butane(DIB)and 5,5'-(terephthaloylbis(azanediyl))diisophthalic acid ligand(BADA).It has been characterized by FT-IR,SEM,XRD,XPS,TG and single crystal X-ray diffraction structural analysis,which confirm its structure,composition and micro morphology.Besides,it can be used as catalyst in the reaction of 2-indolinone with alcohol,in which 3-alkyl 2-indolinone and 3-alkyl-3-hydroxy-2-indolinone can be constructed with good group compatibility,respectively.Another carboxylic acid complex Zr-CICA(3.3b)has been also synthesized based on1-(carboxymethyl)-1H-indole-3-carboxylic acid ligand(CICA).Its structure,composition and micro morphology has been confirmed by FT-IR,TEM,SEM,XRD,XPS and TG.We have explored the catalytic activity of these coordination complexes in borrowing hydrogen reaction based on anilines with alcohols or benzylamines.Zr-CICA is suitable for this reaction,which can be used as catalyst in the formation of C-N bond through brorrowing hydrogen methodology in high isolated yield with broad substrates scope.Besides,Zr-CICA has been confirmed with good recyclability and structural stability as catalyst.P(III)-directed C-H activation of 2-(Diphenylphosphino)-biphenyl derivatives has been developed through[Rh(COD)Cl₂]₂catalysing,in which new phosphones XPhos analogues can be formed from hydroarylation of internal alkynes with 2-(Diphenylphosphino)-biphenyl derivatives.The E-alkenyl mono-and di-substituted XPhos analogues have been obtained respectively in excellent stereoselectivity,whose absolute configurations have been verified by X-ray single crystal diffraction.We are pleased to find that this hydroarylation can tolerate wide scope substrates,in which varieies of 2-(Diphenylphosphino)-biphenyl derivatives with different steric hindrance and electrical properties are compatible.Stereoselective fluoroarylation of 1,1-difluoroallens enabled by Pd(PPh₃)₃Cl₂ catalyst has been also developed,which can introduce alkenyl trifluoromethyl into 1,1-difluoroallens in excellent stereoselectivity verified by NOESY and ¹H-¹⁹F COZY.Varieties'type functional group can be tolerated,such as methoxy,aldehyde,alkyl,halogen and heteroaromatic ring.Free radical capture experiment and ¹⁹F in-situ NMR have been conducted to explore the mechanism of the fluoroaromatization synthesis strategy of1,1-difluoroallene.Besides,we have made some transformation of the template product,(E)-(5,5,5-trifluoropent-3-ene-1,4-diyl)dibenzene,to evaluate this synthetic application of this developed protocol.