Molybdenum(V) on an Oxide String. Synthesis and Structure of the Novel Linear Trinuclear Complex {[MoO(TPP)][O-Mo(TPP)-O][MoO(TPP)]}ClO(4).

The syntheses and crystallographic characterization of the linear trinuclear complex [Mo(3)O(4)(TPP)(3)]ClO(4) and the monomeric precursors [MoO(TPP)(OClO(3))] and [MoO(TPP)(OH(2))]ClO(4) are described. The crystallographic analyses of [MoO(TPP)(OClO(3))] and [MoO(TPP)(OH(2))]ClO(4) show that these similar complexes are typical oxomolybdenum(V)-porphyrin complexes whose only significant structural differences are related to their respective axial ligands. [Mo(3)O(4)(TPP)(3)]ClO(4) is obtained by the controlled hydrolysis of [MoO(TPP)(OClO(3))] or by the direct reaction of [MoO(TPP)(OClO(3))] with {[MoO(TPP)](2)O}. This hydrolysis product contains the novel [Mo(3)O(4)(TPP)(3)](+) ion, which has an unprecedented linear [O=Mo-O-Mo-O-Mo=O](7+) unit and three nearly parallel 24-atom porphyrin mean planes. The central porphyrin is found to be rotated 29.3 degrees and 29.7 degrees with respect to the two terminal porphyrin ligands, which are nearly eclipsed (twist angle 0.44 degrees ). The formation of [Mo(3)O(4)(TPP)(3)]ClO(4) instead of the &mgr;-hydroxo-bridged binuclear complexes obtained from the hydrolysis of analogous mononuclear metalloporphyrin complexes is rationalized on the basis of the greater pi-acceptor ability of Mo(V). Crystal data for [MoO(TPP)(OClO(3)).0.9CH(2)Cl(2): a = 11.437(2) Å, b = 13.567(6) Å, c = 13.764(4) Å, alpha = 89.15(1) degrees, beta = 108.86(1) degrees, gamma = 103.96(2) degrees, triclinic, space group P&onemacr;, Z = 2, T = 293(2) K. Crystal data for [MoO(TPP)(OH(2))ClO(4).1.5C(7)H(8): a = 13.2138(7) Å, b = 13.5959(12) Å, c = 14.6676(11) Å, alpha = 74.292(8) degrees, beta = 69.114(8) degrees, gamma = 69.030(5) degrees, triclinic, space group P&onemacr;, Z = 2, T = 127(2) K. Crystal data for [Mo(3)O(4)(TPP)(3)]ClO(4).C(6)H(1)(4).3.4CH(2)Cl(2).4H(2)O: a = 26.428(6) Å, b = 18.683(6) Å, c = 28.692(4) Å, beta = 113.98(2) degrees, monoclinic, space group P2(1)/c, Z = 4, T = 127(2) K.