Cooperative Ge-N Bond Activation in Aluminium-Functionalised Aminogermanes and Spontaneous Imine Elimination via an Intermediate Germyl Cation

作者：Uhl Werner^*; Tannert Jens; Honacker Christian; Layh Marcus; Qu Zheng Wang; Risthaus Tobias; Grimme Stefan

来源：Chemistry - A European Journal, 2015, 21(6): 2638-2650.

DOI：10.1002/chem.201405989

• bond activation
• density functional calculations
• germanium
• hydroalumination
• imines

Hydrometallation of iPr(2)NGe(CMe3)(CCCMe3)(2) with HM(CMe3)(2) (M=Al, Ga) affords alkenyl-alkynylgermanes in which the Lewis-acidic metal atoms are not coordinated by the amino N atoms but by the -C atoms of the ethynyl groups. These interactions result in a lengthening of the GeC bonds by approximately 10pm and a comparably strong deviation of the GeCC angle from linearity (154.3(1)degrees). This unusual behaviour may be caused by steric shielding of the N atoms. Coordination of the metal atoms by the amino groups is observed upon hydrometallation of Et2NGe(C6H5)(CCCMe3)(2), bearing a smaller NR2 group. Strong MN interactions lead to a lengthening of the GeN bonds by 10 to 15pm and a strong deviation of the M atoms from the MC3 plane by 52 and 47pm, for Al and Ga, respectively. Dual hydrometallation is achieved only with HAl(CMe3)(2). In the product, there is a strong AlN bond with converging AlN and GeN distances (208 vs. 200pm) and an interaction of the second Al atom to the phenyl group. Addition of chloride anions terminates the latter interaction while the activated GeN bond undergoes an unprecedented elimination of EtNC(H)Me at room temperature, leading to a germane with a GeH bond. State-of-the-art DFT calculations reveal that the unique mechanism comprises the transfer of the amino group from Ge to Al to yield an intermediate germyl cation as a strong Lewis acid, which induces -hydride elimination, with chloride binding being crucial for providing the thermodynamic driving force.

• 出版日期2015-2-2