Department of Chemistry and Polymer Science, University of Stellenbosch, Private Bag X1, Matieland, Stellenbosch 7602, South Africa.
Chemistry. 2011 Aug 29;17(36):9944-56. doi: 10.1002/chem.201101213. Epub 2011 Jul 22.
Quantum chemical calculations have been performed for the dicoordinated carbon compounds C(PPh(3))(2), C(NHC(Me))(2), R(2) C=C=CR(2) (R = H, F, NMe(2)), C(3)O(2), C(CN)(2)(-) and N-methyl-substituted N-heterocyclic carbene (NHC(Me)). The geometries of the complexes in which the dicoordinated carbon molecules bind as ligands to one and two AuCl moieties have been optimized and the strength and nature of the metal-ligand interactions in the mono- and diaurated complexes were investigated by means of energy decomposition analysis. The goal of the study is to elucidate the differences in the chemical behavior between carbones, allenes and carbenes. The results show that carbones bind one and two AuCl species in η(1) fashion, whereas allenes bind them in η(2) fashion. Compounds with latent divalent carbon(0) character can coordinate in more than one way, with the dominant mode indicating the degree of carbone or allene character. The calculated structures of the mono- and diaurated tetraaminoallenes (TAAs) reveal that TAAs exhibit a chameleon-like behavior: The bonding situation in the equilibrium structure is best described as allene [(R(2)N)(2)]C=C=C[(NR(2))(2)] in which the central carbon atom is a tetravalent C(IV) species, but the reactivity suggests that TAAs should be considered as divalent C(0) compounds C{C[(NR(2))(2)]}(2), that is, as "hidden" carbones. Carbon suboxide binds one AuCl preferentially in the η(1) mode, whereas the equilibrium structures of the η(1)- and η(2)-bonded diaurated complex are energetically nearly degenerate. The doubly negatively charged isoelectronic carbone C(CN)(2)(2-) binds one and two AuCl very strongly in characteristic η(1) fashion. The N-heterocyclic carbene complex, [NHC(Me)(AuCl)], possesses a high bond dissociation energy (BDE) for the splitting off of AuCl. The diaurated NHC adduct, [NHC(Me)(AuCl)(2)], has two η(1)-bonded AuCl moieties that exhibit aurophilic attraction, which yield a moderate bond strength that might be large enough for synthesizing the complex. The BDE for the second AuCl in [NHC(Me)(AuCl)(2)] is clearly smaller than the values for the second AuCl in doubly aurated carbone complexes.
已针对二配位碳化合物 C(PPh(3))(2)、C(NHC(Me))(2)、R(2) C=C=CR(2) (R = H、F、NMe(2))、C(3)O(2)、C(CN)(2)(-) 和 N-甲基取代的 N-杂环卡宾 (NHC(Me)) 进行了量子化学计算。优化了二配位碳分子作为配体与一个和两个 AuCl 部分结合的配合物的几何形状，并通过能量分解分析研究了单和二金化配合物中金属-配体相互作用的强度和性质。该研究的目的是阐明 carbones、allenes 和 carbenes 之间化学行为的差异。结果表明 carbones 以 η(1)方式结合一个和两个 AuCl 物种，而 allenes 以 η(2)方式结合它们。具有潜在二价碳(0)特性的化合物可以以不止一种方式配位，主导模式表明 carbone 或 allene 特性的程度。单和二金化四氨基 allenes (TAAs)的计算结构表明，TAAs 表现出变色龙行为：平衡结构中的成键情况最好描述为 allene [(R(2)N)(2)]C=C=C[(NR(2))(2)]，其中中心碳原子是四价 C(IV)物种，但反应性表明 TAAs 应被视为二价 C(0)化合物 C{C[(NR(2))(2)]}(2)，即“隐藏”的 carbones。碳亚氧化物优先以 η(1)方式与一个 AuCl 结合，而 η(1)-和 η(2)-键合的二金化配合物的平衡结构在能量上几乎是简并的。带两个负电荷的等电子 carbone C(CN)(2)(2-)以特征性的 η(1)方式非常强烈地结合一个和两个 AuCl。N-杂环卡宾配合物 [NHC(Me)(AuCl)] 具有拆分 AuCl 的高键离解能 (BDE)。二金化 NHC 加合物 [NHC(Me)(AuCl)(2)] 具有两个 η(1)-键合的 AuCl 部分，表现出金亲性吸引，产生适度的键强度，足以用于合成该配合物。[NHC(Me)(AuCl)(2)] 中第二个 AuCl 的 BDE 明显小于双金化 carbone 配合物中第二个 AuCl 的 BDE。
