Details

Autor(en) / Beteiligte

• Dodonov, Vladimir A.
• Chen, Weixing
• Zhao, Yanxia
• Skatova, Alexandra A.
• Roesky, Peter W.
• Wu, Biao
• Yang, Xiao‐Juan
• Fedushkin, Igor L.

Titel

Gallium “Shears” for C=N and C=O Bonds of Isocyanates

Ist Teil von

• Chemistry : a European journal, 2019-06, Vol.25 (35), p.8259-8267

Ort / Verlag

Germany: Wiley Subscription Services, Inc

Erscheinungsjahr

2019

Quelle

Wiley-Blackwell Journals

Beschreibungen/Notizen

• Digallane [L1Ga−GaL1] (1, L1=dpp‐bian=1,2‐[(2,6‐iPr2C6H3)NC]2C12H6) reacts with RN=C=O (R=Ph or Tos) by [2+4] cycloaddition of the isocyanate C=N bonds across both of its C=C−N−Ga fragments to afford [L1(O=C−NR)Ga−Ga(RN−C=O)L1] (R=Ph, 3; R=Tos, 4). The reactions with both isocyanates result in new C−C and N−Ga single bonds. In the case of allyl isocyanate, the [2+4] cycloaddition across one C=C−N−Ga fragment of 1 is accompanied by insertion of a second allyl isocyanate molecule into the Ga−N bond of the same fragment to afford compound [L1Ga−Ga(AllN− C=O)2L1] (5) (All=allyl). In the presence of Na metal, the related digallane [L2Ga−GaL2] (2; L2=dpp‐dad=[(2,6‐iPr2C6H3)NC(CH3)]2) is converted into the gallium(I) carbene analogue [L2Ga:]− (2 A), which undergoes a variety of reactions with isocyanate substrates. These include the cycloaddition of ethyl isocyanate to 2 A affording [Na2(THF)5]{L2Ga[EtN−C(O)]2GaL2} (6), cleavage of the N=C bond with release of 1 equiv. of CO to give [Na(THF)2]2[L2Ga(p‐MeC6H4)(N−C(O))2−N(p‐MeC6H4)]2 (7), cleavage of the C=O bond to yield the di‐O‐bridged digallium compound [Na(THF)3]2[L2Ga‐(μ‐O)2‐GaL2] (8), and generation of the further addition product [Na2(THF)5][L2Ga(CyNCO2)]2 (9). Complexes 3–9 have been characterized by NMR (1H, 13C), IR spectroscopy, elemental analysis, and X‐ray diffraction analysis. Their electronic structures have been examined by DFT calculations. Isocyanate scission by Ga species: [L1Ga−GaL1] (1, L1=dpp‐bian) reacts with isocyanates RNCO by [2+4] cycloaddition, whereas [L2Ga−GaL2] (2, L2=dpp‐dad) is inert. Gallylene [L2Ga:]− (2 A) (generated from 2 and sodium metal), however, is highly reactive towards isocyanates. Interestingly, digallane 1 exclusively attacks the N=C bonds of RNCO, whereas with RNCS only the S=C bonds are affected. Depending on the nature of RNCO, the gallylene 2 A may cleave either its N=C or its O=C bond.