The Role of Ligands in Oxidative Addition Chemistry of Low-Valent Main Group Derivatives: Not Only Stabilization but Also Activation

At present, the use of low-valent derivatives of the
main group
elements, including metallylenes, etc., in catalysis as an alternative
to transition metals is widely discussed. The high reactivity of these
compounds often requires their stabilization by using electron-pair
donor ligands. The influence of the latter on oxidative addition reactions
is usually not considered. In this work, to the best of our knowledge
for the first time, using the example of the oxidative insertion of
Lappert’s germylene into PhSSPh in the presence of N, S, P,
and O donor ligands, we show that the ligands significantly increase
the reaction rate. This can be associated with an increase in the
level of the germylene highest occupied molecular orbital under the
influence of a donor. Qualitatively, the obtained values of the reaction
rate constants correlate well with the germylene oxidation potentials
in the presence of ligands or ligand oxidation potentials.

目前，以主族元素的低价衍生物（包括类金属烯等）替代过渡金属用于催化的相关研究已被广泛讨论。这类化合物通常具有较高反应活性，往往需要借助电子对给体配体实现稳定化。而这类配体对氧化加成反应的影响通常未被纳入考量。本研究中，据我们所知，首次以拉佩特锗烯（Lappert’s germylene）在N、S、P、O型电子对给体配体存在下，向二苯基二硫醚（PhSSPh）中发生氧化插入反应为例，证明配体可显著提升该反应的速率。这一现象可归因于给体配体作用下，锗烯的最高占据分子轨道（Highest Occupied Molecular Orbital, HOMO）能级升高。从定性角度来看，所测得的反应速率常数数值，与配体存在时锗烯的氧化电位，或是配体自身的氧化电位均呈现良好的相关性。