Bernd Klingert’s scientific contributions

The title metallocenium salts form crystalline 2:1 host:guest inclusion compounds with-cyclodextrin, [(5-C5H5)2M]PF6 2-CD 8H2O (1, M = Fe;2, M = Co;3, M = Rh). The X-ray crystal structures of1 and3, and the lattice constants, crystal system and space group of2 have been determined. Crystal data: triclinic, space groupP1 (No. 1),Z = 1;1,a = 13.865 (2) ,b = 13.839 (2) ,c = 15.520 (2) , = 91.43 (2), = 85.81 (2), = 120.22 (2), andR F = 0.089 for 4257 observed MoK reflections [I > 3(I)];2,a = 13.810 (2) ,b = 13.872 (2) ,c = 15.560 (2) , = 93.99 (2), = 87.06 (2), = 120.04 (2);3,a = 13.756 (1) ,b = 13.863 (1) ,c = 15.561 (2) , =94.39 (1), = 86.92 (1), = 119.89 (1), andR F = 0.061 for 11142 observed MoK reflections [I > 3(I)]. In the crystals of1 and3, two -cyclodextrin molecules are arranged head-to-head to form a dimer by means of intermolecular hydrogen bonding across the secondary hydroxyl faces of adjacent -CD monomers. The dimers are stacked along the crystallographicc axis to form a channel-type structure. The metallocenium cation is encapsulated within the cavity of the dimer, while the PF 6 – anion is located outside the cavity, being centered between the primary hydroxyl faces of adjacent dimers. Eight water molecules of hydration per asymmetric unit reside in the spaces between the -CD columns. In view of the almost identical crystal data for2 a similar structure can be assumed for the cobaltocenium adduct.

Inclusion compounds of a range of cyclopentadienyl (arene)iron(II) sandwich complexes, structurally related ferrocenes and (tetramethylcyclobutadiene) cobalt complexes with α-, β- or γ-cyclodextrin (α-, β-, γ-cd) have been prepared. Complexes bearing sterically demanding ring ligands were selectively included in β- or γ-cd. X-Ray crystallographic studies of seven new α-cd adducts demonstrate that the molecular packing of the α-cd macrocycles in channel-type structures depends on the size and shape of the guest complexes. Crystal structure determinations of two of the β-cd adducts reveal a channel type structure similar to that of the corresponding α-cd adducts, although in these cases the exact orientation of the guest molecules could not be determined due to disorder.

The mixed-sandwich complex [(η5-C5H5)Fe(η6-C 6H6)]PF6 forms crystalline 2:1 host:guest inclusion compounds with α- and β-cyclodextrin (α-CD, β-CD) respectively. The compounds have been characterized by UV-Vis, circular dichroism, and CP/MAS 13C NMR spectroscopy. The crystal structure of the α-cyclodextrin adduct has been determined by single-crystal X-ray diffraction. [(η5-C5H5)Fe(η6-C 6H6)]PF6. 2α-CD·8H2O: triclinic, space group P1, a = 13.815 (1) Å, b = 13.929 (1) Å, c = 15.639 (2) Å, α = 94.23 (1)° β = 87.15 (1)°, γ = 119.81 (1)°, V = 2603.9 Å3, and Dcalcd = 1.55 g cm-3 for Z = 1. The parameters could be refined by the full-matrix least-squares method to the final R value of 0.083 for 9965 reflections with I > 2σ(I). In the crystal, two α-cyclodextrin molecules form a head-to-head dimer by means of intermolecular hydrogen bonding across the secondary hydroxyl faces of adjacent α-cyclodextrin monomers. The [(η5-C5H5)Fe(η6-C 6H6)]+ cation is encapsulated within the cavity of the dimer and is tilted by an angle of 39° (C5H5)/40° (C6H6) against the mean planes of the α-CD molecules. The cyclopentadienyl and the benzene rings are parallel; Fe-centroid distances to the C5H5 and the C6H6 rings are 1.66 and 1.57 Å, respectively. The PF6- anion is located at the center of the primary hydroxyl side of the α-cyclodextrin molecule that includes the benzene ring. The dimers are stacked along the crystallographic c axis to form a channel-type structure. Eight water molecules of hydration per asymmetric unit fill the intermolecular space between the α-cyclodextrin dimers, forming a hydrogen-bond network within the crystal.