Lewis-base adducts of dichlorodioxomolybdenum (VI) and dimethyldioxomolybdenum (VI) react in an equilibrium reaction with excess t-butylhydroperoxide (TBHP) under the formation of a seven-coordinated molybdenum (VI) complexes displaying a η1-alkylperoxo- ligand. HCl/CH4 elimination or the protonation of the Lewis-base ligand is not observed, the TBHP hydrogen atom is instead transferred to one of the terminal oxo ligands under the ...