Batchelor Anna G, Marks Joshua H, Ward Timothy B, Duncan Michael A
Department of Chemistry, University of Georgia, Athens, Georgia 30602, United States.
J Phys Chem A. 2024 Oct 7;128(41):8954-63. doi: 10.1021/acs.jpca.4c05304.
Co(CH) ( = 1-6) complexes produced with laser vaporization in a supersonic molecular beam are studied with infrared photodissociation spectroscopy and computational chemistry. Infrared spectra are measured in the C-H stretching region using the method of tagging with argon atoms to enhance the photodissociation yields. C-H stretch vibrations for all clusters studied are shifted to lower frequencies than those of the well-known acetylene vibrations from ligand → metal charge transfer interactions. The magnitude of the red shifts decreases in the larger clusters as the interaction is distributed over more ligands. Computational studies identify various unreacted complexes with individual acetylene ligands in cation-π bonding configurations as well as reacted isomers in which ligand coupling reactions have taken place. Infrared spectra are consistent only with unreacted structures, even though the formation of reacted structures such as the metal ion-benzene complex is highly exothermic. Large activation barriers are predicted by theory along the reaction coordinates for the = 2 and 3 complexes, which inhibit reactions in these smaller clusters, and this situation is presumed to persist in larger clusters.
通过在超声分子束中进行激光汽化产生的Co(CH)（= 1 - 6）配合物，利用红外光解离光谱和计算化学进行了研究。使用氩原子标记法在C - H伸缩区域测量红外光谱，以提高光解离产率。与配体→金属电荷转移相互作用相比，所有研究的团簇的C - H伸缩振动都向低频移动，频率低于著名的乙炔振动。随着相互作用分布在更多配体上，较大团簇中的红移幅度减小。计算研究确定了阳离子 - π键合构型中具有单个乙炔配体的各种未反应配合物，以及发生了配体偶联反应的反应异构体。红外光谱仅与未反应结构一致，尽管金属离子 - 苯配合物等反应结构的形成是高度放热的。理论预测了 = 2和3配合物沿反应坐标的大活化能垒，这抑制了这些较小团簇中的反应，并且这种情况在较大团簇中可能持续存在。
