Transition metal chalcogenide and pnictide nanocrystals are of interest for optoelectronic and catalytic applications. Here, we present a generalized route to the synthesis of these materials from the silylative deoxygenation of metal oxides with trimethylsilyl reagents. Specific nanophases produced in this way include Ni3S2, Ni5Se5, Ni2P, Co9S8, Co3Se4, CoP, Co2P, and heterobimetallic (Ni/Co)9S8. The resulting chalcogenide nanocrystals are hollow, likely due to differential rates of ion diffusion during the interfacial phase transformation reaction (Kirkendall-type effect). In contrast, the phosphide nanocrystals are solid, likely because they form at higher reaction temperatures. In all cases, simultaneous partial decomposition of the deoxygenating silyl reagent produces a coating of amorphous silica around the newly formed nanocrystals, which could impact their stability and recyclability.