Collect. Czech. Chem. Commun. 2003, 68, 2309-2321

Multireference Brillouin-Wigner Coupled Cluster Singles and Doubles (MRBWCCSD) and Multireference Doubles Configuration Interaction (MRD-CI) Calculations for the Bergman Cyclization Reaction

Oscar Rey Puiggrosa, Jiří Pittnera,*, Petr Čárskya,*, Philipp Stampfussb and Wolfgang Wenzelb

a J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Dolejškova 3, 182 23 Prague 8, Czech Republic
b Research Centre Karlsruhe, Institute for Nanotechnology, P.O. Box 3640, D-76021 Karlsruhe, Germany


We used the Bergman cyclization reaction of hex-3-ene-1,5-diyne to 1,4-didehydrobenzene (p-benzyne) as a benchmark system to assess the accuracy of recently developed multireference Brillouin-Wigner coupled cluster singles and doubles method (MRBWCCSD) in comparison with the multireference doubles configuration interaction (MRD-CI) calculations using the same geometry and basis set. Activation and reaction enthalpies were calculated. We found good agreement between experiment and theory at the MRCI+Q/CCSD(T) level of theory, provided a sufficiently large polarized basis set is used (cc-pVTZ). The MRBWCCSD theory gives results of a somewhat lower accuracy, presumably because of the absence of T3 clusters in the cluster expansion.

Keywords: Bergman reaction; Enediynes; Multireference coupled clusters; Multireference configuration interaction; p-Benzyne; Ab initio calculations.

References: 62 live references.