Infrared spectrum of matrix isolated ClSiO and ab initio calculations

Abstract

Articles you may be interested inEffect of matrix on IR frequencies of acetylene and acetylene-methanol complex: Infrared matrix isolation and ab initio study

BAC-MP4 Predictions of Thermochemistry for Gas-Phase Compounds in the Si−H−O−Cl System

“…Stewart and Gordon also calculated the heat of formation for Cl 2 SiO, obtaining −121.2 kcal mol -1 from the semiempirical MNDO-PM3 method and −110.1 kcal mol -1 from a calculation at the MP2/6-31G(d) level; the latter value is in very good agreement with the BAC-MP4 prediction. Bond lengths and angles predicted by DFT methods are in good agreement with the HF/6-31G(d) geometry reported here; both indicate a bent structure for ClSiO and a short Si−O bond in Cl 2 SiO consistent with double-bond character. − …”

“…Both values are considerably more negative than the BAC-MP4 prediction, as well as calculated values reported by others. Heats of formation for these molecules were calculated by Junker and Schnöckel using density functional theory (DFT; B3LYP/TZVPP), yielding values (298 K) of −105.2 kcal mol -1 6 and −39.96 kcal mol -1 , , respectively. Their value for Cl 2 SiO is about 6 kcal mol -1 more positive than that of the BAC-MP4 model, while DFT prediction for ClSiO is in good agreement with it.…”

“…The high temperatures used indicate that a large number of silicon-containing species may be involved, including silicon oxyhalides and compounds containing multiple silicon atoms. − In contrast with silane oxidation/combustion, which has been extensively studied, very little is known about the thermochemistry and kinetics of species involved in SiCl 4 oxidation. Thermodynamic data (heats of formation, entropies, and heat capacities) for silicon oxyhalides are almost totally unavailable; in the Si−O−Cl system of monomeric silicon compounds, only two oxychloride species have been characterized: ClSiO , and Cl 2 SiO. − Reaction rates relevant to SiCl 4 oxidation in the literature largely concern either qualitative observations or global reaction rates. ,− Several investigations of the pyrolysis of chlorinated silanes have recently appeared, − however, and reaction rates of SiCl 2 and SiCl 3 with molecular oxygen have been reported. The overall lack of information represents a major barrier to the construction of mechanisms composed of elementary chemical reactions.…”

“…Theoretical methods are now fully capable of providing molecular thermochemistry with sufficient accuracy for modeling purposes (±2 kcal mol -1 ). The literature contains several reports describing ab initio quantum-chemistry predictions of chlorinated silane thermochemistry; − only a few applications to silicon oxychlorides are reported, however. ,, In this paper we present the results of applying the bond additivity correction method at the level of fourth-order Møller−Plesset perturbation theory (BAC-MP4) to the prediction of thermochemical data for Si−H−O−Cl compounds. Prior to this investigation, we employed this method to predict thermochemistry for compounds in the related Si−H−Cl, , Si−O−H, and Si−C−O−H systems.…”

2 Matrix isolation

“…In a solid argon matrix at 16 K Cl atoms and SiO molecules react to form the hitherto unknown ClSiO molecule. 215 This displays n(SiO) and n(SiCl) bands at 1160.9 and 509.4 cm 21 . It is a non-linear molecule with a ClSiO bond angle around 125° and an Si-Cl bond which is significantly weaker than that in Cl 2 SiO.…”