Molybdenum(V) on an Oxide String. Synthesis and Structure of the Novel Linear Trinuclear Complex {[MoO(TPP)][O−Mo(TPP)−O][MoO(TPP)]}ClO4

The syntheses and crystallographic characterization of the linear trinuclear complex [Mo3O4(TPP)3]ClO4 and the monomeric precursors [MoO(TPP)(OClO3)] and [MoO(TPP)(OH2)]ClO4 are described. The crystallographic analyses of [MoO(TPP)(OClO3)] and [MoO(TPP)(OH2)]ClO4 show that these similar complexes are typical oxomolybdenum(V)−porphyrin complexes whose only significant structural differences are related to their respective axial ligands. [Mo3O4(TPP)3]ClO4 is obtained by the controlled hydrolysis of [MoO(TPP)(OClO3)] or by the direct reaction of [MoO(TPP)(OClO3)] with {[MoO(TPP)]2O}. This hydrolysis product contains the novel [Mo3O4(TPP)3]+ ion, which has an unprecedented linear [OMo−O−Mo−O−MoO]7+ unit and three nearly parallel 24-atom porphyrin mean planes. The central porphyrin is found to be rotated 29.3° and 29.7° with respect to the two terminal porphyrin ligands, which are nearly eclipsed (twist angle 0.44°). The formation of [Mo3O4(TPP)3]ClO4 instead of the μ-hydroxo-bridged binuclear complexes obtain...