A variable-low-temperature scanning tunneling microscope (STM) was used to observe oxygen (O-2), ethylene (C2H4), and acetylene (C2H2) molecules on a Ag(110) surface and the various complexes that were formed between these two hydrocarbons and oxygen at 13 K. Ethylene molecule(s) were moved to the vicinity Of O-2 either by STM tunneling electrons at 13 K or thermally at 45 K to form (C2H4)(x)-O-2 (X = 1-4) complexes stabilized by C-H center dot center dot center dot O hydrogen bonding. Acetylene-oxygen complexes involving one or two acetylene molecules were observed.