Arsine and its fluoro, chloro derivatives: a computational thermochemical study

Abstract

The structures, vibrational frequencies, enthalpies of formation and dissociation energies of arsine, arsenic hydrides and their fluoro, chloro derivatives have been studied using density functional B3LYP/cc-pVDZ, ab-initio MP2/cc-pVDZ and composite CBS-QB3 and CBS-Q methods. Computed standard enthalpies of formation at 298 K by atomisation scheme are compared with reported values. Bond dissociation energies at 0 K are calculated for all possible thermal dissociation of the molecular species in gas phase, from which the energetically most favourable dissociation pathways are predicted. The calculated enthalpies of formation and bond dissociation energies are correlated with the nature of bonding in arsine and its fluoro, chloro derivatives. Energy barriers at 0 K are calculated and transition states are located for the molecular fragment elimination of the thermal dissociation reactions.

Arsenic(III) chloride ammonolysis

“…The experimentally determined value of the As-Cl bond dissociation energy in an AsCl 3 molecule is 73.0 kcal/mol [11], which is well consistent with our calculations ( Table 4). The As-Cl bond in AsCl 3 is less strong than the As-H bond in AsH 3 (76.4 kcal/mol [6]). The dissociation energy increases in going to a more electronegative substitu ent that has a small atomic radius (116.3 kcal/mol [6]).…”

“…The As-Cl bond in AsCl 3 is less strong than the As-H bond in AsH 3 (76.4 kcal/mol [6]). The dissociation energy increases in going to a more electronegative substitu ent that has a small atomic radius (116.3 kcal/mol [6]). In our case, the As-NH 2 bond dissociation energy is far lower than the As-Cl bond dissociation energy and remains virtually unchanged in going from Cl 2 AsNH 2 to As(NH 2 ) 3 (Table 3).…”

“…Bagchi et al [6] used the MP2/cc pVDZ complex method to determine the As-Cl bond dissociation energy in an AsCl 3 molecule and obtained an underes timate, namely 65.6 kcal/mol. The experimentally determined value of the As-Cl bond dissociation energy in an AsCl 3 molecule is 73.0 kcal/mol [11], which is well consistent with our calculations ( Table 4).…”

“…Those methods are comparatively robust even when applied to many electron systems such as arsenic compounds [6]. Table 1 displays the geometrical parameters of arsenic chlorides, amides, and imides as calculated by B3LYP/6 311+G(d,p).…”

“…The geometrical parameters of the initial com pounds, intermediates, transition states (TSs), and final products were determined by the density func tional (DFT) method using the B3LYP functional and the 6 311+G(d,p) valence split basis set with diffu sion and polarization functions [4,6]. This method was also employed to calculate the IR frequencies for arsenic compounds and transition states.…”