Soluble Silver Acetylide for the Construction and Structural Conversion of All-Alkynyl-Stabilized High-Nuclearity Homoleptic Silver Clusters

Silver
acetylide complex [Ag­(ArCC)]n (Ar
= 3,5-di-tert-butylphenyl) with unprecedented
high solubility in common organic solvents has been designed and synthesized.
The high solubility is due to two bulky tert-butyl
substituents on the phenyl ring. This feature is significant to construct
and isolate single crystals of all-alkynyl-stabilized silver clusters,
which are crucial to investigate the intrinsic binding interaction
and coordination modes between Ag­(I) and ethynide ligands. Crystallization
of [Ag­(ArCC)]n under various conditions
resulted in three high-nuclearity homoleptic silver acetylide clusters,
namely, [Ag21(ArCC)20]­(OH) (1), [Ag16(ArCC)16] (2),
and [Ag15(ArCC)15] (3).
Complex 1 has a [Ag21] cluster protected by
twenty 3,5-di-tert-butyl-phenylethynide ligands.
Complexes 2 and 3 have neutral [Ag16] and [Ag15] clusters, respectively. In addition to these
homoleptic silver clusters, two new silver acetylides [Ag20(ArCC)16(CH3COO)4] (4) and [Ag22(ArCC)16(NO3)4(CH3CH2OH)4]­(OH)2 (5) were synthesized. The acetate and nitrate
anions in these structures are more like counterions instead of acting
as critical building blocks or templates for cluster assembly. These
results illustrated the significance of 3,5-di-tert-butyl-phenylethynide ligands in the construction and stabilization
of high-nuclearity silver clusters. Analysis of structures of 1–5 revealed several novel coordination
modes between Ag­(I) and ethynide ligands, which contributed considerably
to our knowledge of Ag­(I)–ethynide binding interactions.

本研究设计并合成了一种乙炔银配合物[Ag(ArC≡C)]ₙ（其中Ar为3,5-二叔丁基苯基），该配合物在常见有机溶剂中具有前所未有的高溶解度。其高溶解度源于苯环上的两个大位阻叔丁基取代基。这一特性对于构建与分离全炔基稳定的银簇单晶具有重要意义，而这类银簇对于探究Ag(I)与炔基配体（ethynide）之间的内在结合相互作用及配位模式至关重要。通过调控不同结晶条件，从[Ag(ArC≡C)]ₙ中获得了三个高核同配体乙炔银簇合物，分别为[Ag₂₁(ArC≡C)₂₀](OH)（1）、[Ag₁₆(ArC≡C)₁₆]（2）以及[Ag₁₅(ArC≡C)₁₅]（3）。配合物1为由20个3,5-二叔丁基苯乙炔基配体（3,5-di-tert-butyl-phenylethynide）保护的[Ag₂₁]簇合物；配合物2与3则分别为中性的[Ag₁₆]与[Ag₁₅]簇合物。除上述同配体乙炔银簇合物外，本研究还合成了两种新型乙炔银配合物：[Ag₂₀(ArC≡C)₁₆(CH₃COO)₄]（4）与[Ag₂₂(ArC≡C)₁₆(NO₃)₄(CH₃CH₂OH)₄](OH)₂（5）。上述结构中的乙酸根与硝酸根阴离子更多起到抗衡离子的作用，而非簇合物组装过程中的关键构筑单元或模板。上述结果证实了3,5-二叔丁基苯乙炔基配体在高核银簇的构筑与稳定化过程中的重要作用。通过对1至5号簇合物结构的解析，本研究发现了数种Ag(I)与炔基配体之间的新型配位模式，这极大丰富了我们对Ag(I)-炔基配位相互作用的认知。