A Stable Open‐Shelled Au26 Nanocluster with Remarkable Performance in Selective Oxidation of Benzyl Alcohol

Abstract Open metal sites are crucial in catalysis. We have used a “loose coordination strategy” (LCS) to preorganize open metal sites in gold cluster catalysts. A gold nanocluster with composition of [Au 26 (3,4‐Me 2 ‐Ph‐form) 9 ( i Pr 2 ‐imy) 3 (Me 2 S)](BF 4 ) 2 ( i Pr 2 ‐imy=1,3‐Diisopropylimidazolium tetrafluoroborate, 3,4‐Me 2 ‐Ph‐form=N,N′‐Di(3,4‐dimethyl‐phenyl)formamidine) ( Au 26 ) has been obtained by one pot synthesis, i.e. the direct reduction of Me 2 SAuCl in the presence of N‐heterocyclic carbenes and amidinate ligands. ESI‐TOF‐MS reveals that the Me 2 S ligand is detached from the cluster to form open sites. The accessibility of the exposed Au atoms has been confirmed quantitatively by luminescent titration with 2‐naphthalenethiol. Surprisingly, Au 26 has 15 valence electrons, and the presence of an unpaired electron is confirmed by superconducting quantum interference device (SQUID) and electron paramagnetic resonance (EPR). This open‐shelled Au 26 not only shows unexpected high stability but also exhibits excellent catalytic performance toward the selective oxidation of benzyl alcohol to benzaldehyde, achieving a remarkable turnover number up to 100670.