The singlet-triplet energy separation in silylene

MCSCF calculations followed by large scale configuration interaction, comparable with the best done for isovalent methylene, give a singlet-triplet splitting in silylene of 21.0±1 kcal/mol. The singlet is the lower energy state. Structural parameters for the as yet unobserved triplet are r e=1.48±0.005 Å and θe=118. 5±1°. © 1986 American Institute of Physics.