The molecular structure, equilibrium conformation and barrier to internal rotation in decachloroferrocene, Fe(η-C5Cl5)2, determined by gas electron diffraction

Abstract

The molecular structure of decachloroferrocene has been determined by gas electron diffraction supported by quantum chemical calculations. The equilibrium conformation has staggered ligand rings and D(5d) symmetry. The barrier to internal rotation is, however, only 0.8(2) kJ mol⁻¹. This barrier is so low that even at room temperature the vast majority of molecules in the gas phase would have sufficient thermal energy to undergo virtually non-hindered internal rotation. While the eclipsed equilibrium conformation of unsubstituted ferrocene is determined by attractive dispersion interaction between the two cyclopentadienyl ligands, the staggered equilibrium conformation of Fe(η-C₅Cl₅)₂ is due to steric repulsion between Cl atoms at different rings. The ligands are non-planar: the C-Cl bonds are bent 3.7(3)° out of the plane of the C₅ ring away from the metal atom. The Fe-C, C-C and C-Cl bond distances (r(a)) are: 205.0(4) pm, 143.4(3) pm and 170.2(4) pm respectively.

Encapsulation of small magnetic clusters in fullerene cages: A density functional theory investigation within van der Waals corrections

“…For all TM m @C n systems, the smallest TM-C distances are in the range from 2.08 to 2.30Å, which is typical for the bond lengths of Fe, Co, and Ni atoms with C atoms in metal complexes, e.g., 2.06Å for Fe-C in Fe(C 5 Cl 5 ) 2 . 58 For most cases, the TM atoms bind to the center of the hexagonal or pentagonals, which maximizes the coordination number of the TM atoms.…”

Synthesis and Spectroscopic Characterization of the Four Complete Series [(C5XnH5‐n)Fe(CO)2R] (X= Cl, Br; R= Me, Ph; n= 1–5). Molecular and Crystal Structures of [(C5X5)Fe(CO)2R]

“…However, the distances from Fe to the cyclopentadienyl ring centroids as well as the carbonyl C−O bonds are slightly longer in the phenyl compounds. There are no other crystal structures containing a [Fe(C 5 Cl 5 )] unit, however, there is a gas phase electron diffraction study of [(C 5 Cl 5 ) 2 Fe] [23] . In this compound the average C−Cl distance is 1.702(4) Å and the iron‐centroid distance is 1.648 Å.…”

“…There are no other crystal structures containing a [Fe(C 5 Cl 5 )] unit, however, there is a gas phase electron diffraction study of [(C 5 Cl 5 ) 2 Fe]. [23] In this compound the average CÀ Cl distance is 1.702(4) Å and the iron-centroid distance is 1.648 Å. Two different studies describe crystal structures containing a [Fe(C 5 Br 5 )] unit: one is about pentabromoferrocene, [19d] the other on nona-and decabromoferrocene.…”

meso-Bis{η5-1-[1-(dimethylamino)ethenyl]-3-(trimethylsilyl)cyclopentadienyl}iron(II) and the cobalt(II) analogue

“…Conformational preferences appear to be even more delicately balanced by the interannular repulsive interactions, metal-ring distances, substitutents on the Cp rings etc. (Okuda, 1991;Phillips et al, 2010).…”