We previously reported a size-focusing conversion of poly-disperse gold nanoparticles carped by phosphine into monodisperse [Au-25(PPh3)(10)(SC2H4Ph)(5)Cl-2](2+) nanoclusters in the presence of phenylethylthiol. Herein, we have determined the crystal structure of [Au-25(PPh3)(10)(SC2H4Ph)(5)Cl-2](2+) nanoclusters and also identified an portant side-product-a Au(I) complex formed in the size focusing process. The [Au-25(PPh3)(10)(SC2H4Ph)(5)Cl-2](2+) cluster features a vertex-sharing bi-icosahedral core, resembling a rod. The formula of the Au(I) complex is determined to be [Au-2(PPh3)(2)(SC2H4Ph)](+) by electrospray ionization (ESI) mass spectrometry, and its crystal structure (with SbF6- counterion) reveals Au-Au bridged by -SC2H4Ph and with terminal bonds to two PPh3 ligands. Unlike previously reported [Au-2(PR3)(2)(SC2H4Ph)](+) complexes in the solid state, which exist as tetranuclear complexes (i.e., dimers of [Au-2(PR3)(2)(SC2H4Ph)](+) units) through a Au center dot center dot center dot Au aurophilic interaction, in our case we found that the [Au-2(PPh3)(2)(SC2H4Ph)](+) complex exists as a single entity, rather than being dimerized to form a tetranuclear complex. The observation of this Au(I) complex allows us to gain insight into the intriguing conversion process from polydisperse Au nanoparticles to monodisperse Au-25 nanoclusters.