Amphiphilicity in Oxygen Atom Transfer Reactions of Oxobis(iminoxolene)osmium Complexes
Amphiphilicity in Oxygen Atom Transfer Reactions of Oxobis(iminoxolene)osmium Complexes
复制标题
Oxobis(iminoxolene)锇配合物的氧原子转移反应中的两亲性
DOI：
10.1021/acs.inorgchem.1c00068
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发表时间：
2021
影响因子：
4.6
通讯作者：
Brown, Seth N.
中科院分区：
文献类型：
--
作者：
Erickson, Alexander N.;Gianino, Jacqueline;Markovitz, Sean J.;Brown, Seth N.
氧代双（亚胺恶茂）锇（VI）化合物（Rap）2 OsO（Rap = 2-（4-RC 6 H4 N）-4，6-tBu 2C 6 H2O）容易被膦和亚磷酸酯脱氧，得到五配位（Rap）2 Os（PR′3）或六配位（Rap）2 Os（PR′3）2。结构数据表明，这种净双电子还原伴随着亚间恶茂配体的明显氧化，这是因为它们更有能力参与向还原的脱氧形式的锇络合物提供π。在（Rap）2 Os（PR′3）2中，HOMO是基于配体的亚间恶茂氧化还原活性轨道的组合，而LUMO是高度共价的金属-亚间恶茂π* 轨道。在反式异构体中，HOMO需要通过对称性被配体定位，而在顺式异构体中，配体采用使HOMO中的金属-配体π* 相互作用最小化的构象。动力学研究表明，脱氧涉及磷（III）试剂对五配位氧代配合物的速率决定攻击。改变亚间恶茂配体或三芳基膦上的芳基的取代基对氧原子转移的速率几乎没有影响，氧原子转移速率和氧代配合物的HOMO-LUMO间隙之间显示出最佳的相关性。这表明锇氧代基团在其与磷（III）试剂的氧原子转移反应中显示出亲电和亲核特性之间的平衡。
Oxobis(iminoxolene)osmium(VI) compounds (Rap)2OsO (Rap = 2-(4-RC6H4N)-4,6-tBu2C6H2O) are readily deoxygenated by phosphines and phosphites to give five-coordinate (Rap)2Os(PR′3) or six-coordinate (Rap)2Os(PR′3)2. Structural data indicate that this net two-electron reduction is accompanied by apparent oxidation of the iminoxolene ligands due to their greater ability to engage in π donation to the reduced deoxy form of the osmium complex. In (Rap)2Os(PR′3)2, the HOMO is a ligand-based combination of the iminoxolene redox-active orbitals, while the LUMO is a highly covalent metal-iminoxolene π* orbital. In the trans isomer, the HOMO is required to be ligand-localized by symmetry, while in the cis isomer, the ligands adopt a conformation that minimizes metal–ligand π* interactions in the HOMO. Kinetic studies indicate that the deoxygenations involve the rate-determining attack of the phosphorus(III) reagent on the five-coordinate oxo complexes. Varying the substituents of the aryl groups on the iminoxolene ligands or on the triarylphosphines has little effect on the rate of oxygen atom transfer, with the best correlation shown between oxygen atom transfer rates and the HOMO–LUMO gap of the oxo complexes. This suggests that the osmium oxo group shows a balance between electrophilic and nucleophilic character in its oxygen atom transfer reactions with phosphorus(III) reagents.