The trianion Z(3-) obtained from 9-phenyl 2,3,7-trihydroxyfluor-6-one, ZH(3), affords dioxomolybdenum and dioxotungsten derivatives which contain [4 + 4] metallocycles of composition [(MO2)(4)Z(4)](4-) (M = Mo, W) in combination with a variety of counter cations. The syntheses, structures and ESMS of the following compounds are presented: compound 1, (MePPh3)(3)(NBu4)[(MoO2)(4)Z(4)]; compound 2, (MePPh3)(3)(NBu4)[(WO2)(4)Z(4)]; compound 3, (MePPh3)(4)[(WO2)(4)Z(4)]; compound 4, (PPh4)(2)(NBU4)(2){(MoO2)(4)Z(4)]; compound 5, (AsPh4)(3)(NBu4)[(MoO2)(4)Z(4)]; compound 6, (AsPh4)(2)-(NBu4)(2)[(WO2)(4)Z(4)]; compound 71 (Ph3PNPPh3) (NBU4)(3)-[(MoO2)(4)Z(4)]; compound 8, (Ph3PNPPh3)(NBu4)(3)[(WO2)(4)Z(4)]; compound 9, (NEt4)(NBu4)(3)[(MoO2)(4)Z(4)]. The metallocycles in all of these compounds have similar structures, with the four metal centers located at the corners of a square slightly distorted, to varying degrees, toward a rhombus and also toward a tetrahedron. Various cations are bound inside the anionic metallocycles. ESI mass spectrometry shows that the metallocycles remain intact in the gas phase, forming [(MO2)(4)Z(4)](4-), {X-[(MO2)(4)Z(4)]}(3-) and in some cases {X-2-[(MO2)(4)Z(4)]}(2-) where X is an organic cation.