Main group bis-element sandwiches formed by donor-acceptor interactions of MCp and ECp (M = Li, Na, K; E = B, Al, Ga) have been studied at the B3LYP/pVDZ level of theory. The most stable are boron-containing species which are stabilized by electrostatic interactions, while other compounds are destabilized. The stability of the donor-acceptor bond decreases in the row B > Al > Ga for donors and Li > Na > K for acceptors. The Cp* group enhances donor properties by 10-15 kJ mol ^-1. We predict that these new compounds are viable synthetic targets.