中文摘要：

使用密度泛函B3LYP以及分子轨道MP2和CCSD（T）方法，研究了Pd（PH3）2催化炔烃硫氰化的可能反应路径。对于异构化、插入和还原消除基元反应步骤，这3种方法给出了相似的结果。对应氧化加成反应，B3LYP水平单膦和双膦路径是竞争的，而MP2和CCSD（T）水平双膦路径更有反应优势。从电子给予和电子反馈角度研究了HS—CN与Pd（PH3）2和Pd（PH，）的氧化加成反应以及炔烃与Pd—B键的插入反应的电子机理。研究结果表明，炔烃与Pd—S或Pd—CN插入反应的区域选择性与S的P轨道有很大关系，因为从S的未杂化双占据p轨道到联烯π’反键的电子反馈作用使得Pd—s比Pd—CN更容易发生炔烃插入反应。

英文摘要：

The reaction mechanisms of Pd（O） -catalyzed alkyne cyanothiolation are examined in this paper, using MP2, CCSD（T） and B3LYP density functional methods. Similar results are obtained with these three approaches for isomerization, acetylene insertion and reductive elimination steps. For the oxidative addition, however, the paths between horizontal single phosphine and bisphosphine are competitive using the B3LYP method. While the horizontal bisphosphine path is more advantageous than that of the horizontal single phosphine with CCSD（T） and MP2 approaches. In addition, from the aspects of electron donation and back-donation, we study the oxidative addition of thiocyanate HS- CN to Pd（PH3） 2 and Pd（PH3）, as well as the electronic mechanisms of acetylene insertion into Pd- B. The results indicate that the regioselectivity of the insertion reaction between acetylene and Pd - S or Pd-CN is correlated with S p-orbital＇s characteristics. It is the electron donation from the unhybridized and double-occupied S p-orbital to the alkylene π＊ antibonding orbital makes the Pd-S more prone to alkyne insertion than the Pd-CN.