Rayón Víctor M, Redondo Pilar, Valdés Haydee, Barrientos Carmen, Largo Antonio
Departamento de Química Física y Química Inorgánica, Facultad de Ciencias, Universidad de Valladolid, 47005 Valladolid, Spain.
J Phys Chem A. 2007 Jul 19;111(28):6334-44. doi: 10.1021/jp072434n. Epub 2007 Jun 20.
Cyanides and isocyanides of first-row transition metal M(CN) (M=Sc-Zn) are investigated with quantum chemistry techniques, providing predictions for their molecular properties. A careful analysis of the competition between cyanide and isocyanide isomers along the transition series has been carried out. In agreement with the experimental observations, late transition metals (Co-Zn) clearly prefer a cyanide arrangement. On the other hand, early transition metals (Sc-Fe), with the only exception of the Cr(CN) system, favor the isocyanide isomer. The theoretical calculations predict the following unknown isocyanides, ScNC(3Delta), TiNC(4Phi), VNC(5Delta), and MnNC(7Sigma+), and agree with the experimental observation of FeNC(6Delta) and the CrCN(6Sigma+) cyanide. First-row transition metal cyanides and isocyanides are predicted to have relatively large dissociation energies with values within the range 80-101 kcal mol(-1), except Zn(CN), which has a dissociation energy around 50-55 kcal mol(-1), and low isomerization barriers. A detailed analysis of the bonding has been carried out employing the topological analysis of the charge density and an energy decomposition analysis. The role of the covalent and electrostatic contributions to the metal-ligand bonding, as well as the importance of pi bonding, are discussed.
采用量子化学技术研究了第一行过渡金属M(CN)（M = Sc - Zn）的氰化物和异氰化物，对其分子性质进行了预测。沿着过渡系列对氰化物和异氰化物异构体之间的竞争进行了仔细分析。与实验观察结果一致，晚期过渡金属（Co - Zn）明显更倾向于氰化物排列。另一方面，早期过渡金属（Sc - Fe），除了Cr(CN)体系外，都倾向于异氰化物异构体。理论计算预测了以下未知的异氰化物，ScNC(3Δ)、TiNC(4Φ)、VNC(5Δ)和MnNC(7Σ+)，并与FeNC(6Δ)和CrCN(6Σ+)氰化物的实验观察结果一致。预测第一行过渡金属氰化物和异氰化物具有相对较大的离解能，其值在80 - 101 kcal mol⁻¹范围内，除了Zn(CN)，其离解能约为50 - 55 kcal mol⁻¹，并且异构化势垒较低。利用电荷密度的拓扑分析和能量分解分析对键合进行了详细分析。讨论了共价和静电贡献对金属 - 配体键合的作用以及π键合的重要性。
