Syntheses and Characterization of the New Homoleptic Indium-Polysulfide Complexes [In₂S₂₇]⁴⁻, [In₂S₁₄]²⁻, and [In₂S₁₆]²⁻

The reaction of InCl₃ with K₂S₅ and Ph₄PCl in a 2:5:4 mole ratio in DMF afforded thin pale yellow crystals of (Ph₄P)₄[In₂S₂₇] (I). I crystallizes in the triclinic space group P1̅ (No. 2) with a = 12.276(3) Å, b = 21.849(8) Å, c = 10.852(2) Å, α = 99.57(2)°, β = 112.44(2)°, γ = 79.28(3)°, V = 2628(1) ų (at −90 °C), and Z = 1. The [In₂(s₄)₂(S₆)₂(s₇)]⁴⁻ anion consists of In³⁺ centers in trigonal bipyramidal coordination. Each In atom is chelated by two bidentate polysulfide S₄²⁻ and S₆²⁻ ligands forming a [In(S₄)(S₆)]⁻ unit. Two [In(S₄)(S₆)]⁻ units are bridged by an S₇²⁻ chain forming a dimer. A similar reaction of InCl₃ with K₂S₅ and Ph₄PCl in a slightly different mole ratio of 1:2:1 in DMF afforded pale yellow crystals of (Ph₄P)₂{[In₂S₁₄]_0.5[In₂S₁₆]_0.5} (II). II crystallizes in the triclinic space group P1̅ (No. 2) with a = 10.906(2) Å, b = 11.892(2) Å, c = 21.554(3) Å, α = 89.81(1)°, β = 97.46(1)°, γ = 92.25(1)°, V = 2769(1) ų (at −80 °C), and Z = 2. II is a cocrystallizate of [In₂S₁₄]²⁻ and [In₂S₁₆]²⁻ anions with equal occupancies. The two anions contain tetrahedral In³⁺ centers. The In atoms are bridged by an S²⁻ and an s₅²⁻ ligand to form an eight-membered [In₂S(s₅)]²⁺ ring core in an extreme cradle configuration. The remaining two coordination sites on each In atom are occupied by a S₄²⁻ chelating ligand on one side and a S₄²⁻ or a S₆²⁻ chelating ligand disordered on the other. These complexes show no absorption peaks in the UV/vis region of the spectrum. The solid-state far-IR spectra of the compounds exhibit strong absorptions in the 500−100-cm⁻¹ region due to the S-S and M-S stretching vibrations. Thermal gravimetric analysis data for these compounds are reported.