Functionalized N-heterocyclic Carbene Platinum Complexes: Synthesis And Catalytic Performance For Hydrosilylation

N-heterocyclic carbene platinum complexes?Pt-NHC?have been applied for the hydrosilylation reaction,which showed excellent catalytic performance with stability and recyclability,and these performances could solve the problems in process of hydrosilylation catalyzed by classic platinum catalysts.A series of N-heterocyclic carbene functionalized with a polyether chain and silyl group-platinum???complexes?MPEG-NHC-Pt?have been designed and synthesized.These complexes were characterized by elemental analysis,X-ray photoelectron spectroscopy?XPS?,thermogravimetric analysis?TGA?,infrared spectroscopy?IR?.In addition,these complexes have been applied in the catalytic hydrosilylation of alkenes and alkynes.It is found that these new complexes exhibit excellent activity and stability for hydrosilylation.Along with the increasing of molecular weight of polyether chain,activity,stability and recyclability of catalysts increase.Though the mole ratio of MPEG₂₀₀₀-NHC-Pt complex 3e/styrene reachs 0.005%,the conversion of styrene and the selectivity of?-adduct can still reach 92.9%and 83.3%.The catalytic properties of complexes for the hydrosilylation reaction of different olefins were investigated.Different molecular weight complexes showed similar catalytic performance,but complexes with the longer of the polyether chain showed better adaptability of olefins and hydrosilanes.At last,we investigated the repeatability of these complexes in hydrosilylation of styrene with?Et O?₃SiH or 1-octene with?Et O?₃SiH.MPEG₂₀₀₀-NHC-Pt complex 3e retains excellent catalytic effect after 30runs.MPEG₂₀₀₀-NHC-Pt complex 3e also exhibits excellent catalytic performance in the hydrosilylation of phenylacetylene with chlorosilane or phenyl silane.Another series of N-heterocyclic carbene functionalized with a polyethylene glycol and silyl group-platinum???complexes?PEG-NHC-Pt?have been prepared and applied in the catalytic hydrosilylation of alkenes,alkynes.The results show that these complexes also have excellent catalytic properties.The complexes with longer of polyethylene glycol chain show higher activity with better reusability and adaptability for substrates.Furthermore,PEG-NHC-Pt complex has better reusability in styrene with?Et O?₃SiH and 1-octene with?Et O?₃SiH reactions than that of MPEG-NHC-Pt complex.PEG₂₀₀₀-NHC-Pt complex 4d retains catalytic performance after 22 runs in hydrosilylation of styrene with?Et O?₃SiH or 30 runs in hydrosilylation of 1-octene with?Et O?₃SiH.