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Thermodynamics of the Decomposition Processes of Donor–Acceptor Complexes MX 3 ⋅en⋅MX 3 and MX 3 ⋅en
Author(s) -
Trinh Cong,
Timoshkin Alexey Y.,
Frenking Gernot
Publication year - 2007
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.200600603
Subject(s) - chemistry , endothermic process , enthalpy , dissociation (chemistry) , iodide , halide , reductive elimination , standard enthalpy of formation , ethylenediamine , molecule , acceptor , thermochemical cycle , elimination reaction , inorganic chemistry , computational chemistry , medicinal chemistry , thermodynamics , catalysis , adsorption , organic chemistry , physics , condensed matter physics , hydrogen production
The structural and thermodynamic properties of the donor–acceptor (DA) complexes of Group 13 metal halides (MX 3 ) with ethylenediamine and their decomposition products have been studied theoretically at the B3LYP/LANL2DZ(d,p) level of theory. Gas‐phase dissociation into various components and HX elimination reactions are considered. Both processes are endothermic but favored by entropy. Complexes of 2:1 composition are predicted to be stable in the gas phase up to 640–1000 K. It is found that complexation with the second acceptor molecule lowers the HX elimination enthalpy; in turn, HX elimination increases DA bonding with a second MX 3 molecule. Exceptionally high values of the dissociation enthalpies (310–390 kJ mol −1 ) and HX elimination reactions (360–420 kJ mol −1 ) of the amido compounds MX 2 NHC 2 H 4 NH 2 and MX 2 NHC 2 H 4 NHMX 2 make them important intermediates in the decomposition processes. Dissociation reactions of the complexes are more favorable than HX elimination reactions; however, the subsequent oligomerization and cyclization processes of coordinationally unsaturated amido and imido compounds may facilitate HX elimination. Since HI elimination reactions are predicted to be the least endothermic, and aluminum‐containing compounds have the strongest M–N dissociation enthalpies, it is expected that compounds based on aluminum iodide are promising objects for experimental studies.