Nonvalent interactions in the crystal structures of (Et4N)2[Mo3S7Br6] and (Et4N)(H9O4)[Mo3S7Cl6] clusters

Crystal structures of (Et₄N)₂Mo₃S₇Br₆] (I) and (Et₄N)(H₉O₄)Mo₃S₇Cl₆] (II) clusters belonging to the class of Mo₃S ₇ ⁴⁺ were determined by X-ray diffraction analysis. Crystals I are orthorhombic a=19.106(3), b=12.930(2), c=29.887(5) Å, V=7383(2) ų, space group Pbca, Z=8, d_calc=2.253 g/cm³, R(F)=0.0402, wR(F²)=0.0587 for 2493 F_hkl>4σ. Crystals II are monoclinic, a=17.106(3), b=18.882(4), c=11.006(2), Å, β=126.13(3)°, V=2871.2(9) ų, space group Cc, Z=4, d_calc=2.147 g/cm³, R(F)=0.0181, wR(F²)=0.0445 for 2307 F_hkl>4σ. Structure I has an anion dimer with 3S_ax…Cl=3.258(4)–3.404(4) Å; the dimer is similar to that observed in the structures of A₂M₃X₇Hal₆], A=Ph₄P⁺, Ph₃EtP⁺, and PPN⁺. In structure II, infinite chains of anions bonded by 3S_ax…Cl contacts of 3.183(3)–3.394(3) Å were found. A similar phenomenon was established earlier for the structure of (Et₄N)(H₉O₄)Mo₃S₇Br₆] (III), which is not isostructural to II. Compounds II and III also differ in the structure of the H₉O₄ ⁺ cation: infinite helix in II and pyramid in III.