Lin Jianyan, Du Xin, Rahm Martin, Yu Hong, Xu Haiyang, Yang Guochun
Centre for Advanced Optoelectronic Functional Materials Research and Key Laboratory for UV Light-Emitting Materials and Technology of Ministry of Education, Northeast Normal University, Changchun, 130024, China.
Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 41296, Gothenburg, Sweden.
Angew Chem Int Ed Engl. 2020 Jun 2;59(23):9155-9162. doi: 10.1002/anie.202002339. Epub 2020 Mar 25.
Fluorination is a proven method for challenging the limits of chemistry, both structurally and electronically. Here we explore computationally how pressures below 300 GPa affect the fluorination of several transition metals. A plethora of new structural phases are predicted along with the possibility for synthesizing four unobserved compounds: TcF , CdF , OsF , and IrF . The Ir and Os octaflourides are both predicted to be stable as quasi-molecular phases with an unusual cubic ligand coordination, and both compounds formally correspond to a high oxidation state of +8. Electronic-structure analysis reveals that otherwise unoccupied 6p levels are brought down in energy by the combined effects of pressure and a strong ligand field. The valence expansion of Os and Ir enables ligand-to-metal F 2p→M 6p charge transfer that strengthens M-F bonds and decreases the overall bond polarity. The lower stability of IrF , and the instability of PtF and several other compounds below 300 GPa, is explained by the occupation of M-F antibonding orbitals in octafluorides with a metal-valence-electron count exceeding 8.
氟化是一种在结构和电子方面挑战化学极限的成熟方法。在此，我们通过计算探究低于300吉帕的压力如何影响几种过渡金属的氟化过程。预测出了大量新的结构相，同时还有可能合成四种未观测到的化合物：TcF、CdF、OsF和IrF。Ir和Os的八氟化物预计都以具有不寻常立方配体配位的准分子相形式稳定存在，且这两种化合物形式上都对应于 +8的高氧化态。电子结构分析表明，在压力和强配体场的共同作用下，原本未占据的6p能级能量降低。Os和Ir的价态扩展使得配体到金属的F 2p→M 6p电荷转移得以发生，这增强了M - F键并降低了整体键极性。IrF较低的稳定性以及PtF和其他几种化合物在低于300吉帕时的不稳定性，可通过八氟化物中金属价电子数超过8时M - F反键轨道的占据情况来解释。
