Electronic Interactions in Iminophosphorane Superbase Complexes with Carbon Dioxide

Abstract

Iminophosphoranes or phosphazenes are an important class of compounds with increasing use in synthetic organic chemistry as neutral organic superbases exhibiting low nucleophilicity. Their electronic structure and therefore their properties strongly depend on substitution, but there have been very few theoretical studies devoted to this topic, and more specifically to the formation of electron donor-acceptor complexes of iminophosphoranes with electrophiles. In this work, we have investigated the interaction with carbon dioxide at different ab initio levels. Carbon dioxide usually behaves as a Lewis acid and the reaction with iminiphosphoranes has been described as a nonconventional aza-Wittig process leading to isocyanates. The reaction can be conducted in supercritical CO conditions (carbon dioxide acts as both solvent and reactant), which is a promising strategy in the context of green chemistry. Our calculations have been carried out at the CCSD(T)/aug-cc-pVTZ//MP2/aug-cc-pVTZ level for model systems and at the M06-2X/6-611+G(d,p) level for a larger species used in experiments. The electronic interactions and the interaction energies are analyzed and discussed in detail using the natural bond orbital method. Proton affinities and gas-phase basicities are provided as well.

Solvent and Substituent Effects on the Phosphine + CO2 Reaction

“…There are numerous studies related with CO2 including in catalysis [25], processing polymers [26], engineering [27], absorption processes [28,29], crop development [30], fuels [31], lasers [32], and combustion research [33]. Also, the CO2 molecule has been the subject of investigation from the theoretical point of view [29,34,35]. Our previous studies concerning A•••B complexes with B being CO2 are reported in references [36][37][38][39][40][41].…”

Growth Pattern, Stability, and Properties of Complexes of C2H5OH and nCO2 (n = 1–5) Molecules: A Theoretical Study

“…The usage of supercritical carbon dioxide (scCO 2 ) was early discovered with extensive applications in nanomaterials, chemical engineering, food science, and pharmaceuticals. , Besides the understanding of thermodynamic, kinetic, and critical properties of scCO 2 reactions, the solubility and intermolecular interactions involving scCO 2 are the research subfields that attract great scientific attention because of practical applications. − Comprehensive insight into the interactions involving CO 2 at the molecular level has an important influence on improving technological applications based on scCO 2 . Numerous studies on complexes of organic molecules and CO 2 were conducted to unveil the nature of intermolecular interactions between these molecules. − The >C/SO···C tetrel bond was addressed as the bonding feature of binary complexes formed by carbonyl/sulfoxide compounds and CO 2 . ,, This feature was also investigated for larger complexes with 2–3 CO 2 molecules. , …”