Synthesis and structure of diiron propane-1,3-dithiolate complex with AsPh3 ligand: siteselectivity of the AsPh3 ligand

Abstract

This article reports the synthesis, structure, and site selectivity of the AsPh3 ligands of two Fe2 propane-1,3-dithiolate (PDT) complexes with the AsPh3 ligand. The reaction of Fe2(CO)6(μ-PDT) 1 with 1.0 equivalent AsPh3 at ambient temperature in the presence of Me3NO resulted in a new diiron complex, Fe2(CO)5(AsPh3)(μ-PDT) 2, as red crystals (63%). The reaction of 1 with 5.0 equivalents of AsPh3 under identical conditions gave 2 in 58% yield and Fe2(CO)4(AsPh3)2(μ-PDT) 3 in low yield (11%) as red crystals. The Me3NO-assisted reaction of 2 with five equivalents of AsPh3 gave 3 in moderate yields (42%). Both complexes contain two fused six-membered metallaheterocycles defined by Fe(S‒C‒C‒C‒S), one of them has a chair conformation, and the other attains in a boat conformation. The bulky AsPh3 ligand selectively coordinated the Fe atoms to the apical site, which is sterically less crowded, as ascertained by the crystal structure. The DFToptimized geometry of 2 was similar to its X-ray structure, and the simulated structure parameters were in good agreement with the experimental values. The optimized geometry of 2 was more stable than its isomeric model 4, where the AsPh3 ligand occupies the basal coordination site, by 1.31 kcalmol- 1. The HOMO and LUMO of 2 were more stable than those of model 4. The calculated Wiberg bond indices (WBI) values for the Fe‒Fe and Fe‒As bonds in 2 are higher than those for the structural model 4.

J. Bangladesh Acad. Sci. 50(2); 259–268: June 2026