Theoretical study of the metathesis-like reaction between ditungsten hexaalkoxides and alkynes

Density-functional calculations have been carried out on a metathesis-like reaction between W2 (OR)6 (R = alkyl) and alkynes to give tungsten alkylidyne complexes. Two possible pathways have been taken into consideration: (i) a parallel approach between the reactants to give 1,2-ditungstenacyclobutadiene; (ii) a perpendicular approach to yield a ditungstenatetrahedrane which then flattens giving a 1,3-ditungstenacyclobutadiene. The electronic structure of the compounds involved in the reaction, as well as several energy profiles corresponding to the formation and decomposition of these species, have been investigated in order to study the thermodynamics and kinetics of the metathesis-like reaction. The inclusion of relativistic effects is crucial in order to understand how the reaction proceeds.