Electron Density Analysis of Metal–Metal Bonding in a Ni 4 Cluster Featuring Ferromagnetic Exchange
Electron Density Analysis of Metal–Metal Bonding in a Ni 4 Cluster Featuring Ferromagnetic Exchange
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以铁磁交换为特征的 Ni 4 团簇中金属与金属键合的电子密度分析
DOI：
10.1021/acs.inorgchem.2c03170
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发表时间：
2023
影响因子：
4.6
通讯作者：
Overgaard, Jacob
中科院分区：
文献类型：
--
作者：
Leiszner, Sofie Stampe;Chakarawet, Khetpakorn;Long, Jeffrey R.;Nishibori, Eiji;Sugimoto, Kunihisa;Platts, James A.;Overgaard, Jacob
我们用实验和理论相结合的方法研究了四核簇合物Ni4(NPtBu3)4中金属-金属键的性质，其中四个镍(I)中心参与了强烈的铁磁耦合。在25K下收集的高分辨率单晶同步辐射X射线衍射数据提供了准确的几何结构和多极模型电子密度描述。用分子中原子的量子理论对Ni4N4核中的电子密度进行了拓扑分析，明确地将成键确定为[Ni-N−]4型的八元环，没有直接的Ni-Ni键，这一结果通常被能量密度分布的分析所证实。相反，计算得到的∼0.6中相邻Ni原子之间的键离域指数大于其他桥联金属-金属键的离域指数，这意味着直接的Ni-Ni键。对于直接Ni-Ni键的存在，在相互作用量子原子方法中也发现了类似的支持，这是一种能量分解方案，它表明存在稳定的Ni-Ni键相互作用，其交换关联能量贡献约为Ni-N相互作用的50%。总而言之，虽然相邻的Ni中心之间的直接相互作用太弱，空间约束太小，不能承受拓扑键临界点的特征，但其他连续的测量方法清楚地表明了显著的Ni-Ni键。这些金属-金属键的相互作用很可能是直接的铁磁交换，导致分子的高自旋基态。
We present a combined experimental and theoretical study of the nature of the proposed metal–metal bonding in the tetranuclear cluster Ni4(NPtBu3)4, which features four nickel(I) centers engaged in strong ferromagnetic coupling. High-resolution single-crystal synchrotron X-ray diffraction data collected at 25 K provide an accurate geometrical structure and a multipole model electron density description. Topological analysis of the electron density in the Ni4N4core using the quantum theory of atoms in molecules clearly identifies the bonding as an eight-membered ring of type [Ni–N−]4without direct Ni–Ni bonding, and this result is generally corroborated by an analysis of the energy density distribution. In contrast, the calculated bond delocalization index of ∼0.6 between neighboring Ni atoms is larger than what has been found for other bridged metal–metal bonds and implies direct Ni–Ni bonding. Similar support for the presence of direct Ni–Ni bonding is found in the interacting quantum atom approach, an energy decomposition scheme, which suggests the presence of stabilizing Ni–Ni bonding interactions with an exchange-correlation energy contribution approximately 50% of that of the Ni–N interactions. Altogether, while the direct interactions between neighboring Ni centers are too weak and sterically constrained to bear the signature of a topological bond critical point, other continuous measures clearly indicate significant Ni–Ni bonding. These metal–metal bonding interactions likely mediate direct ferromagnetic exchange, giving rise to the high-spin ground state of the molecule.