Department of Chemistry, Collaborative Innovation Center of Chemistry for Energy Materials, Shanghai Key Laboratory of Molecular Catalysts and Innovative Materials, Fudan University, Shanghai 200433, China.
Institute of Advanced Synthesis, School of Chemistry and Molecular Engineering, Jiangsu National Synergetic Innovation Center for Advanced Materials, Nanjing Tech University, Nanjing 211816, China.
Science. 2018 Aug 31;361(6405):912-916. doi: 10.1126/science.aau0839.
The alkaline earth metals calcium (Ca), strontium (Sr), and barium (Ba) typically engage in chemical bonding as classical main-group elements through their s and p valence orbitals, where is the principal quantum number. Here we report the isolation and spectroscopic characterization of eight-coordinate carbonyl complexes M(CO) (where M = Ca, Sr, or Ba) in a low-temperature neon matrix. Analysis of the electronic structure of these cubic -symmetric complexes reveals that the metal-carbon monoxide (CO) bonds arise mainly from [M(d)] → (CO) π backdonation, which explains the strong observed red shift of the C-O stretching frequencies. The corresponding radical cation complexes were also prepared in gas phase and characterized by mass-selected infrared photodissociation spectroscopy, confirming adherence to the 18-electron rule more conventionally associated with transition metal chemistry.
碱土金属钙（Ca）、锶（Sr）和钡（Ba）通常通过 s 和 p 价轨道作为经典主族元素参与化学成键，其中 是主量子数。在这里，我们报告了在低温氖基质中分离和光谱表征八配位羰基配合物 M(CO)（其中 M = Ca、Sr 或 Ba）。对这些立方 -对称配合物电子结构的分析表明，金属-一氧化碳（CO）键主要源于 [M(d)] → (CO) π 反馈，这解释了观察到的 C-O 伸缩频率的强烈红移。相应的自由基阳离子配合物也在气相中制备并通过质量选择红外光解光谱进行了表征，证实了更符合传统过渡金属化学的 18 电子规则。
