Department of Chemistry, Texas A&M University at Qatar, Doha, Qatar.
Inorg Chem. 2010 Aug 16;49(16):7597-604. doi: 10.1021/ic101123y.
The mechanism and energetics of the displacement of solvent from photolytically generated (eta(5)-DMP)Mn(CO)(2)(Solv) complexes has been studied [DMP = 2,5-dimethylpyrrole, Solv = solvent]. Rate enhancement relative to the eta(5)-cyclopentadienyl (Cp) system is not observed in the displacement of weakly bound solvents. The bond dissociation enthalpies obtained from the kinetic analysis are in good agreement with the values obtained by detailed density functional theory (DFT) calculations. The results indicate that for both the Cp and the DMP based systems the displacement of weakly bound solvents proceeds by a dissociative or I(d) mechanism. This is in sharp contrast to CO displacement from (eta(5)-DMP)Mn(CO)(3), which is known to proceed by an associative mechanism by way of an eta(3) ring slip intermediate. The associative substitution pathway only becomes competitive with the dissociative channel when the Mn-Solv bond dissociation enthalpy is more than 33 kcal/mol.
已研究了光解生成的（η（5）-DMP）Mn（CO）（2）（Solv）配合物中溶剂置换的机理和能量学[DMP=2,5-二甲基吡咯，Solv=溶剂]。在置换弱结合溶剂时，没有观察到相对于η（5）-环戊二烯基（Cp）体系的速率增强。从动力学分析中获得的键离解焓与通过详细密度泛函理论（DFT）计算获得的值非常吻合。结果表明，对于基于 Cp 和 DMP 的体系，弱结合溶剂的置换均通过解离或 I（d）机理进行。这与 CO 从（η（5）-DMP）Mn（CO）3 的置换形成鲜明对比，已知 CO 是通过η（3）环滑动中间体以缔合机理进行置换的。只有当 Mn-Solv 键离解焓大于 33 kcal/mol 时，缔合取代途径才与解离通道具有竞争力。
