Ta亚烷基化合物与Os氧化物间的亚烷基转移反应机理

使用密度泛函理论B3LYP方法研究了金属Ta亚烷基化合物与Os氧化物间的亚烷基转移反应机理.使用B3LYP方法,金属原子采用LanL2DZ基组和赝势,其他原子采用6-31G（d）基组,优化得到了反应物、产物、中间体和过渡态的几何构型.对所得到的结构使用B3LYP方法,金属原子采用包含f轨道的SDDAll基组和赝势,其他原子采用6-311＋＋G（d,p）基组计算了反应的活化Gibbs自由能.研究结果表明,金属Ta亚烷基化合物与Os氧化物间的亚烷基转移反应经由4个基元反应完成,每一基元反应的过渡态都具有四元环结构并且其活化Gibbs自由能都很小,反应在低温下容易完成.研究结果还表明,总反应是放热反应并且第1个基元反应是决速步骤.

Theoretical study on the carbene transfer mechanism between organometallic tantalum and organometallic osmium complexes

Theoretical calculations on the carbene transfer from the organometallic tantalum complexesMe3Ta CH2to the organometallic osmium complexes MeOs(O)2CH2R(R H,But)were carried out by using the density functional theory B3LYP method.The optimal structures for the reactants,transition states,intermediate,and products were located at the B3LYP level with the LanL2DZbasis sets and effective core potentials for the transition metals and with 6-31G(d)basis sets for otheratoms.The single point energies were further evaluated at the B3LYP level with the SDDAll basissets and effective core potential for the transition metals and with 6-311++G(d,p)basis sets forother atoms.Our calculated results show that the carbene transfer from the organometallic tantalumcomplexes Me3Ta CH2to the organometallic osmium complexes MeOs(O)2CH2R involves fourelementary reactions,each of which has a four-membered ring transition state structure.The activeGibbs free energies are quite small,all less than 47kJ/mol,indicating that the carbene transfer reaction from the organometallic tantalum complexes Me3Ta CH2to the organometallic osmium complexes MeOs(O)2CH2R(R H,But)can occur easily at very low temperature.Calculated resultsalso indicate that the first elementary reaction of the four elementary reactions is the rate-determiningstep and the overall reaction is exothermic both for R H and for R But.