Knowledge Bank

The rotational spectrum of a novel monobridged isomer of $Si2H4$, denoted here as $H2SiHSiH$, has been detected by means of Fourier transform microwave spectroscopy in a supersonic molecular beam through the discharge products of silane. On the basis of high-level coupled cluster theory, this isomer is calculated to lie only 7 kcal/mol above disilene $(H2SiSiH2)$, the most stable isomeric arrangement of $Si2H4$, and to be fairly polar, with a calculated dipole moment of $\mu =1.14$ D. The rotational spectrum of $H2SiHSiH$ exhibits closely-spaced line doubling, characteristic of a molecule undergoing high-frequency inversion motion; at the CCSD(T) level of theory the barrier height to inversion is calculated to be 10-11 kcal/mol. Because of its favorable energetics and high polarity with respect to either disilene or silylsilylene, monobridged $Si2H4$ is a good candidate for radioastronomical detection in sources such as $IRC+10216$ where other large silicon-bearing molecules have already been discovered.