  Recent theoretical work has solidified the viability of the collisional
runaway scenario in young dense star clusters for the formation of very massive
stars (VMSs), which may be precursors to intermediate-mass black holes (IMBHs).
We present first results from a numerical study of the collisional runaway
process in dense star clusters containing primordial binaries. Stellar
collisions during binary scattering encounters offer an alternate channel for
runaway growth, somewhat independent of direct collisions between single stars.
We find that clusters with binary fractions >~10% yield two VMSs via
collisional runaways, presenting the exotic possibility of forming IMBH--IMBH
binaries in star clusters. We discuss the implications for gravitational wave
observations, and the impact on cluster structure.
