School of Physics and Chemistry, Research Center for Advanced Computation, Xihua University, Chengdu, China 610039.
Inorg Chem. 2013 Jun 17;52(12):6893-904. doi: 10.1021/ic400797b. Epub 2013 May 30.
Laboratory studies of the interaction of carbon monoxide with organoactinides result in the formation of isolable complexes such as Cp3UCO derivatives (Cp = cyclopentadienyl) as well as coupling reactions to give derivatives of the oligomeric anions C(n)O(n)(2-) (n = 2, 3, 4). To gain some insight into actinide carbonyl chemistry, binuclear cyclopentadienylthorium carbonyls Cp2Th2(CO)n (n = 2 to 5) as model compounds have been investigated using density functional theory. The most favorable such structures in terms of energy and thermochemistry are the tricarbonyl Cp2Th2(η(2)-μ-CO)3 having three four-electron donor bridging carbonyl groups and the tetracarbonyl Cp2Th2(η(4)-μ-C2O2)(η(2)-μ-CO)2 having not only two four-electron donor bridging carbonyl groups but also a bridging ethynediolate ligand formed by coupling two CO groups through C-C bond formation. The bridging infrared ν(CO) frequencies ranging from 1140 to 1560 cm(-1) in these Cp2Th2(CO)n (n = 3, 4) derivatives indicate extremely strong Th→CO back bonding in these structures, corresponding to formally dianionic CO(2-) and C2O2(2-) ligands and the favorable +4 thorium oxidation state. A characteristic of the Cp2Th2(η(2)-μ-CO)3 and Cp2Th2(η(4)-μ-C2O2)(η(2)-μ-CO)2 structures is their ability to add terminal CO groups, preferably to the thorium atom bonded to the fewest oxygen atoms. These terminal CO groups exhibit ν(CO) frequencies in a similar range as terminal CO groups in d-block metal carbonyls. However, these terminal CO groups are relatively weakly bonded to the thorium atoms as indicated by predicted CO dissociation energies of 14 kcal/mol for Cp2Th2(CO)5. Two low energy structures for the dicarbonyl Cp2Th2(CO)2 are found with two separate four-electron donor bridging CO groups and relatively short Th-Th distances of 3.3 to 3.4 Å suggesting formal single bonds and +3 thorium formal oxidation states. However, a QTAIM analysis of this formal Th-Th bond does not reveal a bond critical point thus suggesting a multicenter bonding model involving the bridging CO groups.
实验室研究一氧化碳与有机锕系元素的相互作用，导致形成可分离的配合物，如 Cp3UCO 衍生物（Cp = 环戊二烯基）以及偶联反应，生成寡聚阴离子 C(n)O(n)(2-)（n = 2、3、4）的衍生物。为了深入了解锕系元素羰基化学，我们使用密度泛函理论研究了双核环戊二烯基钍羰基 Cp2Th2(CO)n（n = 2 至 5）作为模型化合物。从能量和热化学的角度来看，最有利的结构是三羰基 Cp2Th2(η(2)-μ-CO)3，它具有三个四电子供体桥接羰基基团，以及四羰基 Cp2Th2(η(4)-μ-C2O2)(η(2)-μ-CO)2，它不仅具有两个四电子供体桥接羰基基团，而且还具有通过 C-C 键形成将两个 CO 基团偶联的桥接乙炔二酸盐配体。这些 Cp2Th2(CO)n（n = 3、4）衍生物中的桥接红外 ν(CO)频率在 1140 至 1560 cm(-1)之间，表明这些结构中存在极强的 Th→CO 反向键合，对应于形式上的二阴离子 CO(2-)和 C2O2(2-)配体以及有利的+4 价钍氧化态。Cp2Th2(η(2)-μ-CO)3 和 Cp2Th2(η(4)-μ-C2O2)(η(2)-μ-CO)2 结构的一个特征是它们能够添加末端 CO 基团，最好是添加到与氧原子结合最少的钍原子上。这些末端 CO 基团表现出与 d 区金属羰基中的末端 CO 基团相似的 ν(CO)频率。然而，这些末端 CO 基团与钍原子的结合相对较弱，如 Cp2Th2(CO)5 的预测 CO 离解能为 14 kcal/mol 所示。发现二羰基 Cp2Th2(CO)2 的两种低能量结构，具有两个独立的四电子供体桥接 CO 基团和相对较短的 Th-Th 距离为 3.3 至 3.4 Å，表明存在形式单键和+3 价钍形式氧化态。然而，对这种形式 Th-Th 键的 QTAIM 分析并未显示键临界点，因此表明涉及桥接 CO 基团的多中心键合模型。
