Potential of Mixed Dipnictogen Molybdenum Complexes in the Self-Assembly of Thallium Coordination Compounds

The coordination chemistry of the homo- and heterodipnictogen tetrahedrane complexes [{CpMo(CO)₂}₂(μ,η^2:2-EE')] (E, E' = P, As, Sb) (A-F) toward Tl[BArF₂₄] ([BArF₂₄]^- = [B(3,5-C₆H₃(CF₃)₂)₄]^-) was studied. Controlled by the used tetrahedranes A-F, and thus depending on the respective pnictogen atoms, the monomers [Tl(η²-A)][BArF₂₄] ([A]Tl) and [Tl(η²-B)][BArF₂₄] ([B]Tl), the double substituted [Tl(η¹-C)₂][BArF₂₄] ([C]Tl) or the even higher aggregated compounds [Tl₂(η²-D)₃(μ,η^2:1-D)(μ,η^1:1-D)][BArF₂₄]₂ ([D]Tl), [Tl₂(η²-E)₂(μ,η^2:1-E)₃] [BArF₂₄]₂ ([E]Tl) and [Tl₂(η²-F)₃(μ,η^2:1-F)₃][BArF₂₄]₂ ([F]Tl) were obtained. Utilization of [BArF₂₄]^- promises additional stabilization of Tl^I via η⁶-coordination of two of its aryl rings as found in compounds [A]Tl, [B]Tl and [C]Tl. Within the series of reactivity of A-F, the heavier congeners D, E and F tend to form larger aggregates in which σ(E-E') bond contributions to the coordination behavior were observed. Interatomic distances suggest the presence of Tl···Tl interactions in [E]Tl and [F]Tl. The features of the respective coordination compounds were studied in the solid-state as well as in solution. For the latter at least a partial dissociation of the assemblies in solution was indicated. The isolated solid-state aggregates are the first examples of heterodipnictogen units as ligands in self-assembled Tl^I-based coordination compounds.