The adsorption of tetrakis(dimethylamido)titanium, TDMAT, on ammonia-saturated Si(100) surfaces at 300 K is followed by infrared (IR) spectroscopy, temperature-programmed desorption (TPD), and density functional calculations. Experimental observations suggest the occurrence of a surface transamination reaction, where an approaching TDMAT molecule reacts with a surface NH X site, eliminating dimethylamine and attaching Ti to the surface N atom. Density functional calculations show that the reaction is thermodynamically possible, and the comparison of predicted vibrational frequencies to spectroscopic features further supports a surface transamination process. The reaction of TDMAT with Si-H surface sites is not found experimentally in agreement with calculations predicting a process less favorable thermodynamically. Since the transamination reaction investigated here can be viewed as the first step in the atomic layer deposition of TiN on silicon, the conditions required for this first step toward the formation of a well-defined Si/TiN interface are discussed. © 2007 American Chemical Society.