Crystalline (NN)C–M(NN) complexes: synthesis, structure, bonding and lability [M = Si, Ge, Sn or Pb; (NN) = 1,2-(ButCH2N)2C6H4]
作者:Barbara Gehrhus、Peter B. Hitchcock、Michael F. Lappert
DOI:10.1039/b005216g
日期:——
Each of the red-brown or red, isomorphous, crystalline adducts (NN)CâM(NN) [(NN) = 1,2-(ButCH2N)2C6H4 and M = Si, Ge, Sn or Pb] has been obtained from the carbene (NN)C and the appropriate silylene, germylene, stannylene or plumbylene M(NN) in benzene and crystallisation from a hydrocarbon. They are monomeric, with the three-co-ordinate Ccarb and M atoms in an almost planar (C) or pyramidal (M) environment. The CâM distances are more than ca. 10% longer than for a typical MIIâC bond in an MR2 molecule. Variable temperature 13C and xM NMR spectra (xM = 29Si, 119Sn or 207Pb) in toluene-d8, as well as for the appropriate M(NN) and C(NN) precursors, have been recorded. The Ccarb and M chemical shift data show that the compounds readily dissociate in solution, their stability decreasing in the sequence Sn > Pb > Si > Ge. From the magnitude of the chemical shifts, their conformation and CâM distances of the adducts, it is concluded that the CâM bond in each adduct is best formulated as being electrostatic in nature, with the carbene moiety as electron donor and the M(NN) fragment as acceptor.
每个红棕色或红色同晶结晶加合物 (NN)C→M(NN) [(NN) = 1,2-(ButCH2N)2C6H4 且 M = Si、Ge、Sn 或 Pb]由卡宾 (NN)C 和适当的亚甲硅基、甲亚甲基、亚锡基或铅亚甲基 M(NN) 在苯中以及从烃中结晶而获得。它们是单体,三配位的 Ccarb 和 M 原子处于几乎平面 (C) 或金字塔形 (M) 环境中。 C–M 距离超过约。比 MR2 分子中典型的 MII-C 键长 10%。记录了甲苯-d8 中以及适当的 M(NN) 和 C(NN) 前体的变温 13C 和 xM NMR 谱(xM = 29Si、119Sn 或 207Pb)。 Ccarb 和 M 化学位移数据表明,化合物在溶液中容易解离,其稳定性按 Sn > Pb > Si > Ge 的顺序递减。从化学位移的大小、加合物的构象和 C–M 距离可以得出结论,每个加合物中的 C–M 键最好表述为静电性质,其中卡宾部分作为电子供体, M(NN) 片段作为受体。