Quintuply bonded [(H)L(iPr)Cr](2) reacts with alkynes RC≡CR (R = Me, Et, Ph, CF(3)) to form exclusively 1 : 1 adducts [(H)L(iPr)Cr](2)(RCCR). All products feature relatively short Cr-Cr distances (1.919-1.962 Å) and elongated C-C bonds (1.315-1.436 Å), consistent with [2+2] cycloaddition reactions. The hydrocarbon adducts are 4-membered metallacycles, the bridging alkynes of which are progressively skewed with respect to the Cr-Cr axis. In contrast, perfluoroalkyne adds across the metal ligand moiety.

Coordinative polymerization of fluorinated olefins is still a challenging task. We analyzed the catalytic properties of diimido chromium VI compounds computationally by density functional methods. It was found that reactivity predictions depend strongly on the density functional chosen for the computations. Therefore, DFT calculations were calibrated to high level wave function theory calculations. Then geometrical parameters, which can be tuned by a ligand, were scanned to elucidate their influence on the catalytic activity. Having arrived at an optimal parameter set, we randomly assembled chromium complexes from a fragments database and automatically checked for their activities. This led to the proposal of three exemplary catalyst candidates.