Intramolecular d¹⁰–d¹⁰ Interactions in a Ni₆C(CO)₉(AuPPh₃)₄ Bimetallic Nickel–Gold Carbide Carbonyl Cluster

The Ni6C­(CO)9(AuPPh3)4 bimetallic carbide carbonyl cluster was obtained from the reaction of [Ni9C­(CO)17]2– with Au­(PPh3)­Cl. It contains a rare carbon-centered (distorted) Ni6C octahedral core decorated by four Au­(PPh3) fragments. These are μ3-bonded to four contiguous Ni3-triangular faces and display weak intramolecular Au···Au d10–d10 interactions. The cluster has been characterized in the solid state on two different solvato crystals, i.e., Ni6C­(CO)9(AuPPh3)4·THF and Ni6C­(CO)9(AuPPh3)4·THF·0.5C6H14. The two solvates show some interesting differences concerning the weak Au···Au contacts. Density functional theory calculations have demonstrated that the presence of the two isomers is related to solid-state packing effects and not to the existence of two double minima in the potential energy surface. This, in turn, confirms that Au···Au d10–d10 interactions are rather soft and thus influenced also by weak van der Waals forces because of the interaction of the cluster with the cocrystallized solvent molecules.Ni₆C(CO)₉(AuPPh₃)₄双金属羰基碳化物簇合物由[Ni₉C(CO)₁₇]²⁻与Au(PPh₃)Cl反应制得。该簇合物拥有罕见的以碳为中心的（畸变）Ni₆C八面体核心，表面修饰有四个Au(PPh₃)基团。这些基团以μ₃-配位模式键合至四个相邻的Ni₃三角形面，并展现出较弱的分子内Au···Au d¹⁰–d¹⁰相互作用。该簇合物已通过两种不同溶剂化物晶体完成固态表征，分别为Ni₆C(CO)₉(AuPPh₃)₄·四氢呋喃（THF）以及Ni₆C(CO)₉(AuPPh₃)₄·THF·0.5C₆H₁₄。这两种溶剂化物在弱Au···Au接触方面存在值得关注的差异。密度泛函理论（Density Functional Theory, DFT）计算表明，两种异构体的存在与固态堆积效应相关，而非势能面上存在两个双极小值。这一结果进一步证实，Au···Au d¹⁰–d¹⁰相互作用属于弱相互作用，因此会因簇合物与共结晶溶剂分子间的相互作用，受到弱范德华力的影响。