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Theoretical Study on the Reactivities of Stannylene and Plumbylene and the Origin of their Activation Barriers
Author(s) -
Su MingDer
Publication year - 2004
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200400413
Subject(s) - endothermic process , exothermic reaction , chemistry , carbene , singlet state , reactivity (psychology) , molecule , computational chemistry , transition state , crystallography , atomic physics , excited state , physics , catalysis , organic chemistry , medicine , alternative medicine , adsorption , pathology
The potential energy surfaces corresponding to the reactions of heavy carbenes with various molecules were investigated by employing computations at the B3LYP and CCSD(T) levels of theory. To understand the origin of barrier heights and reactivities, the model system (CH 3 ) 2 X+Y (X=C, Si, Ge, Sn, and Pb; Y=CH 4 , SiH 4 , GeH 4 , CH 3 OH, C 2 H 6 , C 2 H 4 , and C 2 H 2 ) was chosen for the present study. All reactions involve initial formation of a precursor complex, followed by a high‐energy transition state, and then a final product. My theoretical investigations suggest that the heavier the X center, the larger the activation barrier, and the less exothermic (or the more endothermic) the chemical reaction. In particular, the computational results show that (CH 3 ) 2 Sn does not insert readily into CH, SiH, CH, GeH, or CC bonds. It is also unreactive towards CC bonds, but is reactive towards C≡C and OH bonds. My theoretical findings are in good agreement with experimental observations. Furthermore, a configuration mixing model based on the work of Pross and Shaik is used to rationalize the computational results. It is demonstrated that the singlet–triplet splitting of a heavy carbene (CH 3 ) 2 X plays a decisive role in determining its chemical reactivity. The results obtained allow a number of predictions to be made.