One Step Forward to “Stapled” Bis(phthalocyanine) Metal Complexes:  Synthesis, Characterization, and Redox Properties of Bis(phthalocyaninato)niobium(IV). X-ray Crystal Structure of the Monoelectronically Oxidized Species [Pc₂Nb](I₃)(I₂)_0.5(ClNP)_3.5 (ClNP = 1-Chloronaphthalene)

Bis(phthalocyaninato)niobium(IV) has been prepared and isolated as a monosolvate, [Pc₂Nb]·ClNP (ClNP = 1-chloronaphthalene). It is a light-brown, stable-to-air Nb(IV) (d¹) paramagnetic sandwich-like species, which, upon oxidation by I₂ under mild conditions, undergoes a metal-centered monoelectronic oxidation to give the diamagnetic Nb(V) (d⁰) [Pc₂Nb]⁺ fragment, with formation of saltlike species of formula [Pc₂Nb](I₃)(I₂)0.5(ClNP)_3.5 (I). The structure of I has been elucidated by single-crystal X-ray work. Crystals are triclinic:  formula C₆₄H₃₂N₁₆Nb·I₃·0.5I₂·3.5C₁₀H₇Cl, M = 2194.8, a = 17.702(3) Å, b = 18.708(3) Å, c = 13.504(2) Å, V = 4267.5(13) ų, α = 106.00(2)°, β = 93.39(2)°, γ = 83.26(1)°, Z = 2, space group P1̄. The structure of the [Pc₂Nb]⁺ fragment, “stapled” by two inter-ligand C−C σ bonds (C11A−C11B and C31A−C31B = 1.574(15) Å), together with its color and UV−visible spectral behavior, allows a straightforward assignment of the same “stapled” structure to the unoxidized [Pc₂Nb]. The present niobium sandwiched materials reiterate the peculiar structural findings shown only by the previously reported [Pc₂Ti].