首页|Four-coordinate disilyl cobalt(Ⅱ)complexes with NHC ligation:Synthesis,characterization,and reactivity
Four-coordinate disilyl cobalt(Ⅱ)complexes with NHC ligation:Synthesis,characterization,and reactivity
扫码查看
点击上方二维码区域，可以放大扫码查看
原文链接
NETL
NSTL
万方数据
Silyl cobalt species are putative intermediates in cobalt-catalyzed transformations of hydrosilanes.However,their reactivity has remained poorly understood.Reported here is the investigation on four-coordinate disilyl Co(Ⅱ)complexes with N-hetereocyclic carbene ligation.The reactions of[(ICy)2Co(vtms)](ICy=1,3-dicyclohexylimidazol-2-ylidene,vtms=vinyltrimethylsilane)with pri-mary and secondary hydrosilanes(3 equiv.)furnish the four-coordinate disilyl complexes[trans-(ICy)2Co(SiHRR')2](SiHRR'=SiH2Mes,1;SiH2Ph,2;SiH2Cy,3;SiHPh2,4;SiHEt2,5)in moderate to good yields.The structures of 1,2 and 4 were established by single-crystal X-ray diffraction.Solution mag-netic susceptibility measurement and EPR spectroscopy indicate their low-spin nature(S=1/2).Reactiv-ity studies on 4 led to the establishment of the conversions of 4 to the disilyl dihydride Co(Ⅲ)complex[K(THF)][(ICy)2Co(H)2(SiHPh2)2]n(6)and the fluorosilyl Co(Ⅱ)complex[(ICy)2Co(THF)(SiFPh2)][BF4](7)when 4 was treated with excess amount of K and AgBF4,respectively,in THF.These conversions hint at the high activity of low-valent and high-valent disilyl cobalt species[trans-(ICy)2Co(SiHPh2)2]1-and[trans-(ICy)2Co(SiHPh2)2]2+.Complex 4 is reactive toward terminal alkynes,but inert toward alkenes and internal alkynes.The reactions of 4 with terminal alkynes CyC=CH and Me3SiC=CH(3 equiv.)yield the Co(Ⅱ)complexes[(ICy)2Co(C≡CCy)2](8)and[(ICy)2Co(C=CSiMe3)((SiMe3)C=CH2)](9),respectively,along with H2SiPh2 and alkynylsilanes RC=CSiHPh2(R=Cy,SiMe3),whereas the reaction with 4-CF3C6H4C≡CH(3 equiv.)produce[(ICy)2Co(C=CAr)((Ar)C=CH(SiHPh2)C=CHAr)](Ar=4-CF3C6H4)(10)and H2SiPh2.These reactions are proposed to involve σ-bond metathesis reactions between alkyne C(sp)-H bonds and Co-Si bonds in 4.Complexes 6-10 have been characterized by NMR spectroscopy,X-ray diffraction study,and elemental analysis.
NETL
NSTL
万方数据
