Controlling the site selectivity is a recognized challenge for migrating the C=C bonds over extended carbon skeletons, due to the thermodynamic similarities of positionally isomerized products. Mn-7 allows for the highly regioselective monoisomerization of longer-chain alkenes, even though further migration could be thermodynamically more favourable. Both 1-octene (1p) and 1-dodecene (1t) were isomerized to corresponding 2-alkenes in excellent yield albeit with moderate E:Z ratios. The monoisomerization process is also compatible with functionalities (1r-1t), including cycloalkyl and phenyl.