The formation of adducts involving the bidentate Lewis acid 1,2-bis(chloromercurio)tetrafluorobenzene (1) and small electron rich organic molecules has been investigated. Compound 1 does not form stable adducts with aliphatic aldehydes and can be crystallized in base-free form from acetaldehyde. The X-ray crystal structure of 1 reveals the existence of a highly cross-linked supramolecular structure in which the individual molecules are associated by Hg‚‚‚Cl and Hg‚‚‚F interactions. By contrast, 1 forms an adduct (2) with benzaldehyde. In this adduct, the benzaldehyde molecule acts as a terminal ligand and coordinates one of the mercury centers through the formation of a long Hg-O bond of 2.68(1) Å. The supramolecular structure of 2 is that of a layered compound in which the monomers are held by numerous intermolecular Hg‚‚‚Cl and Hg‚‚‚F contacts. Arene-fluoroarene interactions are also present and involve the aromatic ring of benzaldehyde, which stacks with neighboring tetrafluorophenylene units (centroid distances ) 3.58 and 3.77 Å). Interestingly, compound 1 forms chelate complexes with acetonitrile (3) and propylene oxide (4). As shown by X-ray single-crystal analyses of 3 and 4, the electron rich organic derivatives interact simultaneously with the two mercury centers via formation of long coordination bonds (Hg-N ) 2.82(1) and 2.93(1) Å in 3; Hg-O )2.71(2) and Hg(2)-O ) 2.77(2) Å in 4). As observed in the structure of 2, compound 3 and 4 form layered solids in which the monomers interact by Hg‚‚‚Cl and Hg‚‚‚F contacts. Finally, compound 1 readily catalyzes the polymerization of propylene sulfide.

Incremental addition of DMF or DMSO to a solution of 1,2-bis(chloromercurio)tetrafluorobenzene (3) in acetone results in a change of the 199Hg NMR chemical shift of 3. The titration curves thus obtained can be fitted and indicate the formation of the 1:1 host−guest complexes 3·μ 2 -DMF (4) and 3·μ 2 -DMSO (5). The stability constants of 4 and 5 have been determined and are respectively equal to 1.8 (±0.2) M-1 and 8.0 (±0.8) M-1. The X-ray crystal structures of 4 and 3·μ 2 -acetone (6) have been determined. In the structure of 4, the carbonyl oxygen atom is coordinated to three mercury atoms and has a distorted-tetrahedral geometry. In 6 however, the acetone oxygen is coordinated to only two mercury atoms and exhibits a trigonal-planar geometry. While it is difficult to detect any metrical changes undergone by the organic substrates upon chelation, the IR carbonyl stretching frequency of 4 (νCO 1635 cm-1) and 6 (νCO 1639 cm-1) indicates that the carbon oxygen bond is weakened. Accordingly, the 13C CP/MAS NMR carbonyl carbon chemical shifts of 4 (167 ppm) and 6 (215 ppm) provide evidence for a substantial polarization of the carbonyl. By comparison of the 13C CP/MAS NMR carbonyl carbon chemical shift, the Lewis acidity of 3 toward acetone can be evaluated to be just inferior to that of MgCl2. Finally, both 4 and 6 have complex and highly networked supramolecular structures which result from intermolecular Hg···Cl and Hg···F or Hg···O contacts.

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Dimethyl sulfoxide templates the assembly of 1,2-bis(chloromercurio)tetrafluorobenzene (1) into an internally Lewis acidic microporous solid of composition 1 small middle dot(DMSO)(3) (2). The channels of 2 contain both chelated and solvate DMSO molecules (omitted in the drawing for clarity), which can be partly exchanged with water molecules. The hydration-dehydration of the resulting compound is reversible.