A Face-to-Face Dimer of Au3 Superatoms Supported by Interlocked Tridentate Scaffolds Formed in Au18 S2 (SR)12.

A new sulfur-containing gold cluster, Au18 S2 (STipb)12 , was serendipitously obtained using the bulky thiol, 2,4,6-triisopropylbenzyl mercaptan (TipbSH), as protecting ligands. Single-crystal X-ray diffraction analysis revealed that Au18 S2 (STipb)12 has a deformed octahedral Au6 core clutched by two tridentate S[Au2 (STipb)2 ]3 units in an interlocked manner. Based on density functional theory calculations, we propose that the Au6 core with two electrons is better viewed as a face-to-face dimer of Au3 (1e) superatoms rather than an electronically closed Au6 (2e) superatom. In situ formation of the sulfide anions (S2- ) via C-S bond breakage is ascribed to the steric repulsion between the TipbS ligands.