Bernd Klingert

Fluorine-containing organozinc reagents. II: The crystal structure of (1,1-dichloro-2,2,2-trifluoroethylzinc chloride)•2(dimethylformamide)

Abstract The DMF complex of 1, 1-dichloro-2, 2, 2-trifluoroethylzinc chloride, a key intermediate in the one pot synthesis of CF 3 CCl 2 -substituted alcohols, has been isolated and its structure determined by 13 C NMR spectroscopy and by X-ray diffraction. This is the first X-ray structural study of a perhalogenated alkylzinc halide and the results show the DMF complex to be monomeric.

Molecular encapsulation of transition metal complexes in cyclodextrins. Part 2. Synthesis and crystal structures of 2:1 adducts between α-cyclodextrin and metallocenium hexafluorophosphates [η5-C5H5)2M]PF6(M = Fe, Co, Rh)

The title metallocenium salts form crystalline 2:1 host:guest inclusion compounds withα-cyclodextrin, [(η5-C5H5)2M]PF6 · 2α-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) Å,b = 13.839 (2) Å,c = 15.520 (2) Å,α = 91.43 (2)°,β = 85.81 (2)°,γ = 120.22 (2)°, andRF = 0.089 for 4257 observed MoKα reflections [I > 3δ(I)];2,a = 13.810 (2) Å,b = 13.872 (2) Å,c = 15.560 (2) Å,α = 93.99 (2)°,β = 87.06 (2)°,γ = 120.04 (2)°;3,a = 13.756 (1) Å,b = 13.863 (1) Å,c = 15.561 (2) Å,α =94.39 (1)°,β = 86.92 (1)°,γ = 119.89 (1)°, andRF = 0.061 for 11142 observed MoKα reflections [I > 3δ(I)]. In the crystals of1 and3, two α-cyclodextrin molecules are arranged head-to-head to form a dimer by means of intermolecular hydrogen bonding across the secondary hydroxyl faces of adjacent α-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 PF6− 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 α-CD columns. In view of the almost identical crystal data for2 a similar structure can be assumed for the cobaltocenium adduct.

Molecular encapsulation of transition metal complexes in cyclodextrins. Part 3. Structural consequences of varying the guest geometry in channel-type inclusion compounds

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.