Organorhenium(VII) oxides such as methyltrioxorhenium(VII) (1) and its longer-chain alkyl derivatives form 1:1 and 1:2 adducts with nitrogen-donor Lewis bases. These compounds adopt well-defined structures in the solid state. In solution, they undergo exchange of both the metal-coordinated base ligands and the oxo ligands. The synthesis and crystal structure (X-ray diffraction study) of the amino-functionalized complex O3Re-CH2CH2CH2N(C5H10) (3a) is reported. Crystal data are as follows : monoclinic, space group P2(1)/c, a = 8.327(2) Angstrom, b = 11.516(1) Angstrom, c = 10.864(2) Angstrom, beta = 101.54(7)degrees R = 0.028 for 1747 reflections. Compounds of type 3a are intramolecular base adducts in the solid state, but rigid geometries in solution can only be observed at low temperatures.