Synthesis And Reactivity Of N-Heterocyclic Silylenes

In this dissertation, three novel N-aryl substituted heterocyclic silylenes have beensynthesized and their reactivity toward O2, S8, Se, benzophenone, azobenzene,triphenylphosphine oxide, organic azides and transition-metal complexes werestudied. All new compounds have been fully characterized. Details are as following:1. Three novel N-aryl substituted five-membered heterocyclic silylenes（HCNAr）₂Si （Ar=Dipp （1）; Mes （2）;2,6-Mes₂C₆H₃（3）; Dipp=2,6-iPr₂C₆H₃,Mes=2,4,6-Me₃C₆H₂） have been isolated and structurally characterized.2canslso be prepared by dehydrochlorination of the corresponding cyclicaminochlorosilane.2.1,3-disiladioxetanes [（HCNDipp）₂SiO]₂（4） and [（HCNMes）₂SiO]₂（5） wereprepared by the reactions of silylenes1and2with oxidants （O₂, OPPh₃）.Treatment of1with S8and Se led to the formation of disiletanes[（HCNDipp）₂SiS]₂（6） and [（HCNDipp）₂SiSe]₂（7）3. Reaction of1with benzophenone and azobenzene led to the C-H bond activationof the phenyl ring and the formation of （HCNDipp）₂Si[OCH（Ph）C₆H₄]（8） and（HCNDipp）₂Si[NHN（Ph）C₆H₄]（9）. Silacyclopropene （HCNDipp）₂Si（CPh）₂（10）and silicon pinacolate （HCNDipp）₂Si（OCPh₂）₂（11） were obtained by thereductive coupling reactions of the corresponding dihalides with phenylacetyleneand benzophenone respectively. Silylenes1and2reacted with Ni（COD）2to givethe nickel-silylene complexes [（HCNDipp）₂Si]₂Ni（COD）（12） and[（HCNMes）₂Si]₂Ni（COD）（13）.4. Reaction of1with the terphenyl azide ArN₃（Ar=2,6-Mes₂C₆H₃, Mes=2,4,6-Me₃C₆H₂） in THF yielded the base-free silanimine （HCNDipp）₂Si=NAr（15） with the almost linear Si=N-C geometry in high yield. Reaction of15withsulfur and H₂O resulted in the1,3-addition of S₂to the C₂N₂Si ring and1,2-addition of H₂O to the Si=N bond, respectively.5. Four chlorosilanes with diphenyl phosphorus groups [C₆H₄（NCH₂PPh₂）₂]SiHCl（18）,[C₆H₄（NCH₂PPh₂）₂]SiCl₂（19）,[C₆H₄（NPPh₂）₂]SiHCl （20） and [C₆H₄（NPPh₂）₂]SiHCl （21） have been synthesized and characterized. Thecorresponding silylenes have not been obtained by reduction reactions. Reactionof18with carbene yielded the ionic compound{[C₆H₄（NCH₂PPh₂）₂]SiH[Me₄（CN）₂C]}⁺Cl^-（22）.6. Reaction of four-membered cyclic diaminochlorosilane [PhP（NDipp）₂]SiHCl （23）with2equiv of ItBu resulted in the olefinic C-H bond activation product{[PhP（NDipp）₂]SiH}[C₂H（NtBu）₂C:]（24）. Treatment of23with0.5equiv ofIMe4gave the disilane {[PhP（NDipp）₂]SiH}{ClSi[PhP（NDipp）₂]}（25）.Apparently, the transient diaminosilylene PhP（NDipp）₂]Si was generated in thisreduction reaction.7. Reaction of L₇Li₂（L7=ArNCH₂CH₂Ar, Ar=2,6-Mes₂-C₆H₃） with SiCl₄afforded4-SiCl₃-ArNCH₂CH₂Ar-SiCl₃-4’（26）. Similar reactions were observed inthe reaction of （Ter-NCH₂tBu）Li （Ter=2,6-Mes₂-C₆H₃）（27） with SiHCl₃, SiCl₄,Me₃SiCl and PCl₃. Boron dibromide4-Br₂B-Ter-NHCH₂tBu （31） was prepared bythe reaction of4-Me₃Si-Ter-NHCH₂tBu （30） with BBr₃.8. Ter-NH-SiHCl₂(Ter=2,6-Mes_2-C6_H3)（34）, Ter-NH-BHCl （37）, Ter-NH-BBr2（38） and Ter-NH-BBrOEt （39）（Ter=2,6-Mes₂-C₆H₃） were synthesized and theirreactions with IMe₄（IMe₄=（Me₂CN）₂C） were studied. NHC-coordinated doublebonded species Ter-N=SiHCl·2IMe₄（35） and Ter-N=BOEt·IMe₄（40） have beensynthesized and characterized.