Premium
Solvent stabilization of the edge inversion transition state in tetrahedral molecules
Author(s) -
Dixon David A.,
Arduengo Anthony J.
Publication year - 1988
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.560340814
Subject(s) - chemistry , tetracoordinate , molecule , ab initio , transition state , crystallography , ground state , tetrahedron , ab initio quantum chemistry methods , molecular orbital , computational chemistry , planar , atomic physics , catalysis , organic chemistry , physics , computer graphics (images) , computer science
The edge inversion process in phosphoric acid, PO(OH) 3 has been studied by large scale ab initio molecular orbital theory. Edge inversion of the tetrahedral ground state via a square‐planar transition state requires 69.5 kcal/mol (MP‐2). Addition of two NH 3 solvent molecules to the vacant NLUMO stabilizes the transition state by 45 kcal/mol (MP‐2). The value for ΔH(300K) for the reaction 2NH 3 + PO(OH) 3 → PO(OH) 3 · (NH 3 ) 2 is 24.1 kcal/mol (MP‐2). The complex with two NH 3 molecules is an intermediate. Addition of one NH 3 to PO(OH) 3 leads to an energy lowering of the planar form of 31 kcal/mol. This structure is now a transition state. The value for ΔH(300K) for the reaction NH 3 + PO(OH) 3 → PO(OH) 3 · NH 3 is 38.6 kcal/mol (MP‐2). The complex of PF 3 O with two NH 3 molecules was studied and is an intermediate. The value for ΔH(300K) for the reaction 2NH 3 + POF 3 → POF 3 · (NH 3 ) 2 is only 3.3 kcal/mol (MP‐2). Electron‐donor solvents clearly will stabilize the edge inversion transition state for tetracoordinate main group compounds.