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RISS 인기검색어
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- 저자 : Tumanskii, Boris (검색결과 1 건)
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Sheberla, Dennis,Tumanskii, Boris,Tomasik, Adam C.,Mitra, Amitabha,Hill, Nicholas J.,West, Robert,Apeloig, Yitzhak Royal Society of Chemistry 2010 Chemical Science Vol.1 No.2
<P>Stable <I>N</I>-heterocyclic carbenes and germylenes were allowed to react with a phosphonyl radical, (<I>i</I>-PrO)<SUB>2</SUB>(O)P&z.rad; (<B>7</B>), generated by photolysis of [(<I>i</I>-PrO)<SUB>2</SUB>(O)P]<SUB>2</SUB>Hg. The products were identified by EPR spectroscopy. An unsaturated carbene (<B>1</B>) and germylene (<B>3</B>) react with <B>7</B> at the divalent atom to give unstable radical products (<I>τ</I><SUB>½</SUB> = 0.2 s). A benzo-annulated carbene (<B>4</B>) and a saturated germylene (<B>6</B>) react with <B>7</B> to give more active radicals. An unsaturated (<B>2</B>) and a saturated silylene (<B>5</B>) undergo rapid reaction (in the dark) with [(<I>i</I>-PrO)<SUB>2</SUB>(O)P]<SUB>2</SUB>Hg to yield unusual silyl phosphites. In these cases only secondary radicals were observed. DFT (PBE0/TZVP//B3LYP/6-31+G(d)) calculations of the radical adducts of the different (C, Si, Ge) unsaturated <I>N</I>-heterocyclic divalent species with the phosphonyl radical show that the unpaired electron is delocalized over the five-membered ring; the spin density on the central atoms decreases in the order C, 39% > Si, 14% > Ge, 2%. These trends can be understood in terms of a zwitterionic structure of the radical adducts. The calculations of the radical adducts of <B>4</B>, <B>5</B> and <B>6</B> with <B>7</B> indicate larger spin density on the central atom, 47%, 58% and 42% on C, Si, Ge, respectively.</P> <P>Graphic Abstract</P><P>The geometry, spin density distribution and reactivity of radical adducts of stable <I>N</I>-heterocyclic carbenes, silylenes and germylenes demonstrate a strong dependence on the nature of the heterocycle and on the central atom. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c0sc00143k'> </P>
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