The reaction of a square-planar platinum(II) complex having two bis(2-diphenylphosphinoethyl)phenylphosphine (triphos), [Pt(triphos)2](NO3)2 ([1](NO3)2), with [Au(tu)2]Cl (tu = thiourea) gave a new trinuclear AuI2PtII complex, [{Pt(triphos)2}{Au(tu)}2]Cl2(NO3)2 ([2]Cl2(NO3)2), through the Au-P coordination bond formation. While the [Pt(triphos)2]2+ unit in [1](NO3)2 adopted the trans-meso configuration, only the cis-racemic isomer was observed in [2]Cl2(NO3)2. The 31P NMR spectroscopy indicated a rapid equilibrium among the possible isomers of [1]2+, facilitating the unique trans-to-cis transformation at the PtII center in this system. Additionally, we observed that this structural transformation leads to an enhancement of the emission intensity.