Reactions of 2-(diphenylphosphinomethyl)aniline, H2L2, with (NBu4)[ReOCl4] yield different oxo rhenium(V) complexes depending on the conditions applied. This comprises monomeric compounds such as [ReOCl3(H2L2)] (1), [ReOCl2(OMe)(H2L2)] (2), or [ReO2(H2L2)(2)]Cl (5) as well as the dimeric mu-oxo complex [{ReOCl2(H2L2)}(2)]O] (3) and the oxo-bridged trimer [{ReOCl(H2L2)}O](3) (4). The latter compound represents the first example of a hitherto unknown trinuclear, cyclic oxo(V) core. [{ReOCl(H2L2)}O](3) contains a tensed 6-membered metallacycle, which readily undergoes rearrangements and reactions with additional ligands. Compounds of the compositions 5 and [ReO2(H2L2)(H2L1)]Cl (6) were isolated either from the decomposition of 4 in CH2Cl2/n-pentane or from reactions with 2-(diphenylphosphino)aniline, H2L1.