Department of Chemistry , Aarhus University , Langelandsgade 140 , DK-8000 Aarhus C , Denmark.
Materials Sciences Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States.
Inorg Chem. 2018 Jun 18;57(12):6913-6920. doi: 10.1021/acs.inorgchem.8b00513. Epub 2018 Jun 4.
The tetrahedral cobalt(II) compound (PhP)[Co(SPh)] was the first mononuclear transition-metal complex shown to exhibit slow relaxation of the magnetization in zero external magnetic field. Because the relative populations of the d orbitals play a vital role in dictating the magnitude of the magnetic anisotropy, the magnetic behavior of this complex is directly related to its electronic structure, yet the exact role of the soft, thiophenolate ligands in influencing the d-electron configuration has previously only been investigated via theoretical methods. To provide detailed experimental insight into the effect of this ligand field, the electron density distribution in this compound was determined from low-temperature, single-crystal X-ray diffraction data and subsequent multipole modeling. Topological analysis of the electron density indicates significant covalent contributions to the cobalt-sulfur bonds. The derived d-orbital populations further reveal a fully occupied d orbital, minor d orbital population, and nearly equal population of the d , d , and d orbitals. Notably, we find that an electrostatic interaction between Co(II) and one hydrogen atom from a thiophenolate group in the xz plane increases the energy of the d orbital, leading to the nearly equal population with d and strong magnetic anisotropy.
四面体钴(II)配合物(PhP)[Co(SPh)]是第一个被证明在外磁场为零的情况下表现出磁化缓慢弛豫的单核过渡金属配合物。由于 d 轨道的相对占据对磁各向异性的大小起着至关重要的作用，因此该配合物的磁行为与其电子结构直接相关，但软硫酚配体在影响 d 电子构型方面的确切作用以前仅通过理论方法进行了研究。为了提供详细的实验见解，了解该配体场的影响，从低温单晶 X 射线衍射数据和随后的多极建模中确定了该化合物的电子密度分布。电子密度的拓扑分析表明，钴-硫键具有显著的共价贡献。衍生的 d 轨道占据数进一步揭示了完全占据的 d 轨道、少量的 d 轨道占据数和 d 、d 和 d 轨道的几乎相等的占据数。值得注意的是，我们发现 Co(II)与硫酚基团中一个氢原子在 xz 平面上的静电相互作用增加了 d 轨道的能量，导致 d 轨道的占据数几乎相等，并且具有强磁各向异性。
