The chemistry of 1,1- and 1,3-diiodo neopentanes, precursors to neopentylidene and 2,2-dimethyl propane-1,3-diyl intermediates, respectively, was probed on a Pt(111) single-crystal surface by temperature-programmed desorption (TPD) and reflection-adsorption infrared spectroscopy (RAIRS). The sequential surface activation of the two C-I bonds in those compounds is manifested by the formation of neopentyl iodide and neopentane in TPD experiments. Dosing of the 1,3-diiodo compound at 230 K leads to the formation of the expected cyclic 2,2-dimethyl propane-1,3-diyl intermediate, with the main ring perpendicular to the surface. Activation of the 1,1-isomer, on the other hand, leads to the formation of 2,2-dimethyl propane-1-yl-3-ylidene, presumably via gamma-H elimination from neopentylidene. The surface species that result from 1,1-diiodo neopentane are more reactive and dehydrogenate to a larger extent than those from the 1,3-diiodo analog, but both eventually convert to neopentylidyne. The implications of this chemistry to hydrocarbon catalytic processes such as oil reforming are discussed.