Isotopically selective infrared photodissociation of (trans-2-chloroethenyl)dichloroborane

We have prepared (2-chloroethenyl) dichloroborane and measured its dipole moment at 1.06 ± 0.05 D. Comparison of this value with ab initio quantum mechanical calculations indicates that the trans isomer has been obtained. Infrared absorptions (12 torr and room temperature) occur at 615 m, 816 s, 960 s, 992 m, 1113 s, 1147 m, 1226 s, 1572 s, and 1627 m . cm
^-1
. Absorptions in the 960-992 cm
^-1
range are tentatively assigned to the ν
as
mode of the BCl
2
group and can be excited by a tuned CO
2
laser. Multiple photon absorption in this region results in isotopically selective decomposition of the compound with a quantum efficiency that suggests a chain reaction. Multiple photon isomerization which would avoid chain reactions and the resultant isotopic scrambling, was not definitively observed.