Supramolecular Assemblies of Polyphosphorus Ligands Based on Weak Tl–P and In

A systematic investigation of the coordination behavior of P_n complexes towards the main group Lewis acids Tl⁺ and In⁺ is presented. While the reaction of the tetrahedral P₂ complex [{CpMo(CO)₂}₂(μ,η²:η²-P₂)] (A1) with Tl[TEF] ([TEF] = [Al{OC(CF₃)₃}₄]⁻) leads to the formation of the dicationic complex [Tl₂(A1)₆]²⁺ (1) with a central six-membered Tl₂P₄ ring, the analogous reaction with In[TEF] leads instead to a tetranuclear [In₄(A1)₈]⁴⁺ complex (3) exhibiting a weak In^I–In^I interaction in the solid state. When the Cp^*-analogous P₂ complex [{Cp^*Mo(CO)₂}₂(μ,η²:η²-P₂)] (A2) is reacted with Tl[TEF] the dinuclear complex [Tl₂(A2)₄]²⁺ (2) is formed, containing only four P₂ ligands but also featuring a six-membered Tl₂P₄ ring motif. From the reactions of the cyclo-P₃ complexes [CpM′(CO)₂(η³-P₃)] (M′ = Cr (B1), Mo (B2)) with In[TEF] and Tl[TEF], a series of four isostructural one-dimensional coordination polymers (4a–d) are obtained which exhibit a novel bridging coordination mode of the cyclo-P₃ ligands in the solid state. Additionally, the mixed P_mS_n ligand complex [(Cp^*Mo)₂(μ,η³:η³-P₃)(μ,η²:η²-PS)] (C) was reacted with Tl[TEF] to afford a novel one-dimensional coordination polymer (5), which shows an unprecedented bridging σ-1,3-coordination mode of ligand C towards Tl⁺. The compounds were analyzed by single-crystal X-ray structure determination, elemental analysis, and mass spectrometry, as well as by multinuclear NMR and IR spectroscopy. All products are readily soluble in CH₂Cl₂, despite in many cases being polymeric in the solid state. Multinuclear NMR spectroscopy suggests a highly dynamic coordination behavior in solution, including fast equilibria between different monomeric species, which is also supported by DFT calculations. The one-dimensional polymers 4c and 4d reveal a triplet in the ³¹P{¹H} MAS NMR spectrum at room temperature, which could be explained by fast rotation of the P₃ rings in the solid state.