Theoretical investigation of the structure and vibrational spectrum of the electronic ground state (X)over-tilde(1A′) of HSiCl

The transient HSiCl (monochlorosilylene) is a species for which structure and spectroscopic properties are almost unexplored by quantum chemical methods. In this work, CCSD and CCSD(T) methods in conjunction with Dunning's hierarchy of basis sets are used to investigate both aspects of this biradical. The CCSD(T)/cc-pCVTZ method using analytical second derivatives of the energy in combination with second order perturbation theory to evaluate the anharmonicity shows to be an efficient strategy to calculate its fundamental vibrational frequencies. Especially remarkable for its anharmonic nature is the calculated value for vi (Si-H stretching) which is only 4 cm(-1) bellow than the observed transition. The experimental structure is investigated by analyzing the experimental rotational constants. This latter goal was accomplished reporting high-level ab initio r(e)-structures as well as empirical structural parameters using CCSD(T)/cc-pCVTZ vibrational corrections of the experimental rotational constants.