A Novel Type of [Mo3O9(L*)]5− Anion in the Structure of an Ammonium−Guanidinium Salt of a MoVI Complex with 1-Hydroxyethylidenediphosphonic Acid (H4L)

The synthesis and X-ray analysis of (NH₄)₂[C(NH₂)₃]₃[MoO₃O₉(L^*)] 2.5H₂O have been carried out (L* = L5⁻); the trinuclear anion has an unusual structure with a different number of terminal oxygen atoms in the ’yl’ groups at the molybdenum atoms (two MoO₂ groups and the MoO₃ group), where pairs of MoO₆ octahedra share a common face or vertex; the structure of the [Mo₃O₉(L^*)]⁵⁻ anion is similar to that of one half of the [Mo₆O₁₇(L₂*)]⁸⁻ hexanuclear anion, in which the central bridging oxygen atom O_c is substituted by a terminal O_t.