Reactions of 22 atomic metal cations with the macrocyclic molecule tribenzocyclotriyne (TBC) were studied in the gas phase in the Fourier-transform ion cyclotron resonance spectrometer. Most of the ions underwent association with TBC with good collisional efficiency to give M(TBC)+, with the exceptions of Zn+ and Au+, for which the highly exothermic charge-transfer reaction dominated, and Cs+, which was unreactive. Most of the M(TBC)+ ions attached a second ligand to give M(TBC)2+, presumably the sandwich complex. Cases for which sandwich formation was slow or negligible included several late first-row transition metal ions which probably insert into the TBC cavity, and several other ions (K+, Al+, Pb+) which apparently have poor electronic interaction with the ligand. Periodic trends for both complexation reactions are discussed, and a rationale is advanced for the surprising inefficiency of exothermic charge transfer in most cases.