Synthesis and crystallographic studies of crown thioether complexes of bismuth(III)

Abstract

The pale yellow bismuth(III)–crown thioether complexes BiCl₃·[12]aneS₄1 and BiCl₃·[15]aneS₅·0.5MeCN 2 have been prepared and characterised. An X-ray crystal structure determination of 1 shows the central bismuth atom bonded to three chlorine atoms, Bi–Cl mean 2.571 Å, Cl–Bi–Cl 90.9(1)–94.3(1)°, and all four sulfur atoms of the [12]aneS₄ macrocycle, Bi–S 2.987(3)–3.206(3)Å, in an approximate half-sandwich structure. The four sulfur atoms are exactly coplanar and the bismuth atom sits in a central location over the ring at a distance of 1.87 Å from this plane. This is the first genuine example of endo complexation for [12]aneS₄ involving a p-block element. Compound 1 crystallises in the monoclinic space group P2₁/n with a= 7.985(4), b= 12.956(7), c= 15.278(9)Å, β= 101.47(4)° and Z= 4. 2099 Observed reflections [I/σ(I) 2.0] gave in the final refinement R= 0.037. The structure of BiCl₃·[15]aneS₅·0.5MeCN 2 shows full co-ordination of the [15]aneS₅ macrocycle to the BiCl₃ unit in a half-sandwich arrangement, with two independent identical molecules, Bi–Cl mean 2.565(7)Å, Bi–S 3.057(7)–3.433(7)Å, Cl–Bi–Cl 86.5(2)–93.0(2)° acetonitrile is trapped as lattice solvate. The ligand undergoes a conformational change (exo- to endo-dentate) on complex formation. Compound 2 crystallises in the orthorhombic space group Pbca with a= 16.972(9), b= 15.418(8), c= 30.60(2)Å, and Z= 16. 2951 Observed reflections [I/σ(I) 2.0] gave in the final refinement R= 0.0545. The resulting conformations of the macrocyclic ligands are discussed in terms of gauche/anti preferences and structural comparisons are drawn between 1 and 2 and their oxocrown counterparts.