Department of Chemistry, Texas A&M University at Qatar, Doha, Qatar.
Inorg Chem. 2012 Dec 3;51(23):13041-9. doi: 10.1021/ic302182b. Epub 2012 Nov 15.
The displacement of a CO ligand from an unusually labile rhenium carbonyl complex containing a bidentate carboxyaldehyde pyrrolyl ligand by PPh(3) and pyridine has been investigated. The reaction is found to proceed by an associative, preequilibrium mechanism. Theoretical calculations support the experimental data and provide a complete energetic profile for the reaction. While the Re-CO bond is found to be intrinsically weak in these complexes, it is postulated that the unusual lability of this species is due to the presence of a weak aldehyde Re-O link that can easily dissociate to open a coordination site on the metal center and accommodate an incoming ligand prior to CO loss. The resulting intermediate complex has been identified by IR spectroscopy. The presence of the hemilabile pyrrolyl ligand provides a lower-energy reaction channel for the release of CO and may be of relevance in the design of CO-releasing molecules.
已经研究了含有双齿羧酸醛吡咯配体的异常不稳定铼羰基配合物中 CO 配体被 PPh(3) 和吡啶取代的情况。反应被发现通过缔合的预平衡机制进行。理论计算支持实验数据，并为反应提供完整的能量分布。虽然 Re-CO 键在这些配合物中被发现本质上较弱，但据推测，这种物种的异常不稳定性是由于存在弱的醛 Re-O 键，它可以很容易地解离以打开金属中心的配位位，并在 CO 损失之前容纳进入的配体。通过红外光谱鉴定了所得的中间配合物。半配位吡咯配体的存在为 CO 的释放提供了较低能量的反应通道，这在设计 CO 释放分子时可能是相关的。
