In summary, the intra-cluster Ge-to-Pt electron donation in Pt7Ge2 largely replaces the alumina-to-Pt electron donation observed in Pt7. In Pt7Ge2C2, the electron density shifts toward the C atoms, through synergistic electronic interactions with the Ge. The bonding in both Pt7Ge2 and Pt7Ge2C2 is substantially more ionic than in Pt7, and we propose that this ionic nature helps stabilize the clusters against sintering/ripening by increasing the energy barriers for diffusion of the clusters on the ionic alumina surface and for dissociation of atoms onto the surface, as was previously suggested to rationalize the high stability of PtnSnm clusters. As anticipated from the similarities in TPD, the charge distributions of Pt7Ge2C2 and Pt4GeC2 are also comparable. For the GMs of both clusters, the average Pt charge is -0.17 e in Pt7Ge2C2 vs. -0.13 e in Pt4GeC2, the average Ge charge is +0.82 e in Pt7Ge2C2 vs +0.85 e in Pt4GeC2, and the average C charge is -0.24 e in Pt7Ge2C2 vs. -0.15 e in Pt4GeC2. The similarity in charge distributions between the higher energy isomers is similar to that for the GM. Therefore, it is unsurprising to see Ge induces selflimiting coking in clusters of both sizes (and for Pt11Ge4). Under the joint influence of C and Ge, the Pt becomes less negatively charged, which invites less further coking since carbon functions here as an oxidant. In fact, coking itself (without Ge) causes a similar electronic effect, slightly inhibiting further coking, but the effect of carbon alone is apparently too weak to prevent additional coking in subsequent TPD runs. Ge puts more electrons onto the incorporated C atoms, and that enhances the coke-inhibiting electronic effect. Another conclusion from this analysis is that the tendency for coking to self-limit at 2C/cluster for the PtnGem, regardless of size, is uncorrelated with the tendency of the PtnGemC2 products to have C-C bonds.