The structures and isomerization of silylenoid Ph2SiLi(OBu-t) were studied by density functional theory at B3LYP/6-31G(d) level. Four equilibrium structures and four isomeric transition states were located. Based on the B3LYP/6-31G(d) optimized geometries, the corresponding harmonic vibrational frequencies of transition states were obtained. The stability, reactivity and existence of various equilibrium structures were discussed. (C) 2004 Elsevier B.V. All rights reserved.