Based on the optimized reaction conditions the substrate scope and limitations were investigated. In order to achieve sufficient conversion for a broad variety of substrates the reaction time was extended to 18 h. Starting with aromatic substrates the desired 1,2-isomerized compound were obtained in high yields. Allylbenzene derivatives featuring strong electron donating groups (e.g. -OTMS) to weak electron donating groups (e.g. alkyl moieties) or electron withdrawing groups (e.g. single or multiple fluorine atoms) were all converted successfully to the desired alkenes. A good performance on annulated systems is demonstrated by the isomerization of 1-allylnaphthalene (6a). Halides, ethers and trimethylsilylethers (Table and) were tolerated as well as the presence of a thiophene and furan moieties (Table and). However, it should be noted that 40 °C were required for these heteroaromatic systems. Excellent E-selectivity could be observed for the above-mentioned substrates. No conversion could be observed for unprotected 40 °C a Reaction conditions: Alkene substrate (0.5 mmol), Mn4 (2.5 mol%) and 1,4-dioxane as internal standard (0.13 mmol) in THF-d8 (0.5 mL) at 25 °C for 18 h. Conversion, yield and E/Z ratio was determined by GC-MS and 1 H NMR spectroscopy. n.d. = not detected. phenols such as eugenol (Table ). While high reactivity was achieved for aliphatic systems, a drop in selectivity was observed (Table and). This effect increased to a mere 55:45 E/Z ratio for trimethyl(pent-1-en-3-yloxy)silane (Table ). Gratifyingly, more bulky olefins such as allyladamantane and allyltrimethylsilane underwent facile isomerization to yield 19a and 20a in high yields (Table ). In comparison to the model substrate 1-allyl-4-fluorobenzene a slight decrease in catalytic performance was noted but high E/Z ratios were achieved. A rather drastic decrease in selectivity was noted for the mesityl substrate 10a (Table ). Although excellent yield was upheld, a strong interference of the methyl groups can be presumed from the E/Z ratio being lowered to about 3:2. The conversion of vinylcyclohexane to the trisubstituted olefin ethylidenecyclohexane (Table , 17a) was explored. At room temperature a conversion of 40 % was not exceeded even with an extended reaction time of 36 h. However, heating to 40 °C for 18 h afforded 17a in 99 % yield.