Synthesis and crystal structure of an encapsulated fragment of MoO2 in the unique Mo8 oxo-cluster compound [Mo8O8Cl6(µ3-O)4(OH)2(µ-OH)4(µ-OEt)4(HOEt)4] and its relevance to the sol–gel synthesis of molybdenum oxides

Abstract

Reaction of the dimeric oxomolybdenum(V) complex [Cl₂OMo(µ-OEt)₂(µ-HOEt)MoOCl₂]1 with SbF₃ in toluene followed by overlaying with light petroleum followed an unexpected course to give crystals of the complex [Mo₈O₈Cl₆(µ₃-O)₄(OH)₂(µ-OH)₄(µ-OEt)₄(HOEt)₄]2 in low yield. The crystal structure of 2[triclinic, space group P, a= 10.803(5), b= 11.159(6), c= 11.659(6)Å, α= 69.66(3), β= 64.06(3), γ= 66.258(24)°, Z= 1, R= 0.058, wR₂= 0.143] has been determined and reveals a new structural type for an M₈ cluster which is closely related to the distorted rutile structure adopted by MoO₂. Incorporating two Mo₄ layers connected with each other by a layer of four bridging oxygen atoms in a centrosymmetric arrangement, it serves as a model for intermediates in the sol–gel synthesis of molybdenum oxides.