Breaking chemistry's strongest bond: Can three-coordinate [M{N(R)Ar}3] complexes cleave carbon monoxide?
Breaking chemistry's strongest bond: Can three-coordinate [M{N(R)Ar}3] complexes cleave carbon monoxide?
复制标题
DOI：
10.1002/chem.200601643
复制
发表时间：
2007-01-01
影响因子：
4.3
通讯作者：
Cummins, Christopher C.
中科院分区：
文献类型：
--
作者：
Christian, Gemma;Stranger, Robert;Cummins, Christopher C.
利用密度泛函方法探讨了CO与三坐标Ta-III、W-III和Re-III配合物(模拟实验[M{N（tBu)Ar}(3)]体系）相互作用的反应途径。计算表明，CO与[Re(NH2)(3)]结合时不形成势垒，形成络合物[OC-Re(NH2)(3)]，该络合物相对于反应物稳定约280 kJ mol（-1）。[Ta(NH2)(3)]与CO的氧端结合被仅20 kJ mol（-1）的势垒抑制，随后C-O键自发断裂，形成产物[C-Re(NH2)(3)]和[O-Ta(NH2)(3)]。与[Mo(NH2)(3)]对N-2的类似解理相比，势能表面的显著特征更有利于CO的解理，其放热较小（335 vs. 467 kJ mol(-1)），并且受到明显的势垒（66 kJ mol(-1)）的阻碍。因此，Re-III/Ta-III/CO体系似乎是在温和的实验室条件下切割异常强的C-O键的绝佳候选者。相关的W-III/Ta-III二聚体可以显著削弱CO键，但不会劈裂CO键，当化学反应发生在活化的CO上而不是在强结合的氧化物和碳化物的劈裂产物上时，可能是一个合适的选择。
The reaction pathway for the interaction of CO with three-coordinate Ta-III, W-III and Re-III complexes (modelled on the experimental [M{N(tBu)Ar}(3)] system) has been explored by using density functional methods. Calculations show that CO binds without a barrier to [Re(NH2)(3)], forming the encounter complex [OC-Re(NH2)(3)], which is stabilized by approximate to 280 kJ mol(-1) relative to the reactants. The binding of [Ta(NH2)(3)] to the oxygen terminus of CO is inhibited by a barrier of only 20 kJ mol(-1) and is followed by spontaneous cleavage of the C-O bond to form the products [C-Re(NH2)(3)] and [O-Ta(NH2)(3)]. The salient features of the potential energy surface are more favourable to CO cleavage than the analogous N-2 cleavage by [Mo(NH2)(3)], which is less exothermic (335 vs. 467 kJ mol(-1)) and is impeded by a significant barrier (66 kJ mol(-1)). The Re-III/Ta-III/CO system therefore appears to be an excellent candidate for cleaving the exceptionally strong C-O bond under mild laboratory conditions. The related W-III/Ta-III dimer, which significantly weakens but does not cleave the CO bond, may be a suitable alternative when the chemistry is to be performed on activated CO rather than on the strongly bound oxide and carbide cleavage products.