Mono-oxo Molybdenum(?) And Tungsten(?) Complexes Bearing Chelating Aryloxides:Synthesis,Structure And Ring Opening Polymerization Of Cyclic Esters

With the rapid development of human society,it is urgent to synthesize biodegradable polymer materials.Polycaprolactone is a kind of common biodegradable polyester,and ring-opening polymerization of lactone catalyzed by metal coordination catalyst is an effective method to synthesize this kind of polymer.In this paper,A series of new mono-oxo VI group metal complexes bearing chelating aryloxides was designed and synthesized,and the effect of the complexes on the ring-opening polymerization of cyclic ester was investigated.This paper consists of three parts:Part?:The significance of synthesis of degradable polymer materials.A briefly introduction of the research situation and catalyst system of ring-opening polymerization of cyclic esters.Part?:A series of mono-oxo molybdenum???complexes bearing chelating aryloxides1-4weresynthesizedsupportrdbyi-phenol2,2?-ethylidenebis?4,6-di-tert-butylphenol??L¹H₂?,?,?,??,??-tetrakis?3,5-di-tert-butyl-2-hydroxyphenyl?-p-xyleneH₄?L²H₄?and p-tert-butylcalix[4]areneH₄?L³H₄?,which were characterized by mass spectrometry,NMR,IR,elemental analysis and single-crystal diffraction.At the same time,we explored the ring-opening polymerization fore-caprolactone andd-valerolactone with the complexes 1-4.The results indicate that the complexes 1 and 3 synthesized by ligands L¹H₂ and L²H₄ have relatively high catalytic activity.In the presence of Monomer:Catalyst=500:1,T=130?,t=24 h,the conversion of?-caprolactone was higher than 98%,and more than 99%conversion could be achieved in 24 hours,and the catalytic rate ofd-valerolactone was much lower than?-caprolactone under the same conditions,which was related to the thermodynamic parameters of cyclic ester.Part?:A series of mono-oxo tungsten???complexes bearing chelating aryloxides5-9 were synthesized with the same ligands,and all of the complexes were characterized by mass spectrometry,NMR,IR,elemental analysis and single-crystal diffraction.At the same time,the five complexes were applied to the ring-opening polymerization ofe-caprolactone andd-valerolactone.The results show that polymers obtained from the catalysts 7,8,9 synthesized by L³H₄ are oligomers,which may be related to the structure of calixarene ligands.Compared with molybdenum???complexes 1 and 3,tungsten???complexes 5 and 6 synthesized from the same ligands have much worse catalytic activity.There was little sign of any significant benificial cooperative effect resulting from the second metal centre in the VI binuclear metal complexes synthesized by the same ligand,compared with their mononuclear metal complexes.