The mu-diborolyl triple-decker complex CpCo(mu-1,3-C3B2Me5)PtMe3 was prepared by reaction of the sandwich anion [CpCo(1,3-C3B2Me5)](-) with [PtMe3I](4); according to energy decomposition analysis, attractive interactions between the [CpCo(1,3-C3B2Me5)](-) and [PtMe3](+) fragments are similar to 64% electrostatic and 36% covalent.