Collision-Induced Dissociation of Undecagold Clusters Protected by Mixed Ligands [Au(11)(PPh(3))(8)X(2)](+) (X = Cl, C≡CPh)

[Image: see text] We herein investigated collision-induced dissociation (CID) processes of undecagold clusters protected by mixed ligands [Au(11)(PPh(3))(8)X(2)](+) (X = Cl, C≡CPh) using mass spectrometry and density functional theory calculations. The results showed that the CID produced fragment ions [Au(x)(PPh(3))(y)X(z)](+) with a formal electron count of eight via sequential loss of PPh(3) ligands and AuX(PPh(3)) units in a competitive manner, indicating that the CID channels are governed by the electronic stability of the fragments. Interestingly, the branching fraction of the loss of the AuX(PPh(3)) units was significantly smaller for X = C≡CPh than that for X = Cl. We ascribed the effect of X on the branching fractions of dissociations of PPh(3) and AuX(PPh(3)) to the steric difference.