The Carter–Goddard–Malrieu–Trinquier model (better known as CGMT model) is a model in inorganic chemistry, used for the description and prediction of distortions in multiple bonding systems of main group elements.[1]
Theory
editThe model predicts that if the double bond is homolytically cleaved in a system R1 R2 M = MR3 R4, the two carbene analog fragments resulting therefrom can subsequently be present in both a singlet and a triplet state.[2] Independently, however, the basic state of the fragments may be a triplet or a singlet state. EA Carter and WA Goddard III showed that the binding energy EG results from the bond dissociation energy E int minus the sum of the singlet-triplet excitation energies ΣΔE S → T of the resulting fragments. E GBE = E int - ΣΔE S → T.[1]
This model was extended by G. Trinquier and J. P. Malrieu by the possibility to make statements about the geometry (characterized by the distance between the metal centers r, and the tilt angle θ) of a double bond system due to ΣΔE S → T. As can be seen in the illustration, a coplanar structure (θ = 0 °) is optimal for triplet fragments. For singlet fragments, however, there is a double donor-acceptor bond with an angle of θ close to 45 °.[1]
References
edit- ^ a b c Himmel, Hans-Jörg; Schnöckel, Hansgeorg (2003-02-03). "An Alternative Way of Characterising the Bonding in Compounds Featuring Main-Group Elements and with the Potential for Multiple Bonding: On the Dissociation of Binary Main-Group Hydrides". Chemistry – A European Journal. 9 (3): 748–755. doi:10.1002/chem.200390083. ISSN 1521-3765. PMID 12569467.
- ^ Carter, Emily A.; Goddard, William A. (March 1986). "Relation between singlet-triplet gaps and bond energies". The Journal of Physical Chemistry. 90 (6): 998–1001. doi:10.1021/j100278a006. ISSN 0022-3654.
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