Two Shared Icosahedral Metallacarboranes through Iron: A Joint Experimental and Theoretical Refinement of Mo?ssbauer Spectrum in [Fe(1,2-C2B9H11)2]Cs

Mo??ssbauer and X-ray photoelectron spectroscopies (XPS) are complemented with high-level quantum-chemical computations in the study of the geometric and electronic structure of the paramagnetic salt of the metallacarborane sandwich complex [Fe(1,2-C2B9H11)2]Cs = FeSanCs. Experimental 57Fe isomer shifts and quadrupole splitting parameters are compared with the theoretical prediction, with good agreement. The appearance of two sets of Cs(3d) doublets in the XPS spectrum, separated by 2 eV, indicates that Cs has two different chemical environments due to ease of the Cs(+) cation moving around the sandwich complex with low-energy barriers, as confirmed by quantum-chemical computations. Several minimum-energy geometries of the FeSanCs structure with the correspond-ing energies and Mo??ssbauer parameters are discussed, in particular the atomic charges and spin population and the surroundings of the Fe atom in the complex. The Mo??ssbauer spectra were taken at different temperatures showing the presence of a low-spin Fe atom with S = 1/2 and thus confirming a paramagnetic FeIII species.

Automated summary

High-level quantum-chemical computations were performed in combination with Mo??ssbauer and X-ray photoelectron spectroscopies to investigate the geometric and electronic structure of the paramagnetic salt [Fe(1,2-C2B9H11)2]Cs = FeSanCs. Comparisons between experimental 57Fe isomer shifts and quadrupole splitting parameters and theoretical predictions showed good agreement. The presence of two sets of Cs(3d) doublets in the XPS spectrum indicated the existence of two different chemical environments for Cs due to the easy movement of the Cs(+) cation around the sandwich complex.