The 2:1 adducts of (benzoylmethylene)triphenylphosphorane with fumaric and terephthalic acids.

Co-crystals of the ylide (benzoylmethylene)triphenylphosphorane (BPPY) with either fumaric acid, viz. (benzoylmethylene)triphenylphosphorane-fumaric acid (2/1), C(26)H(21)OP.0.5C(4)H(4)O(4), or terephthalic acid, viz. (benzoylmethylene)triphenylphosphorane-terephthalic acid (2/1), C(26)H(21)OP.0.5C(8)H(6)O(4), have a stoichiometric ratio of 2:1 between the ylide and the corresponding dicarboxylic acid. In both adducts, the acid component lies across a centre of inversion. In neither case is the ylide protonated by the organic acid; instead the H atoms of the non-ionized dicarboxylic acid molecules participate in the formation of strong O-H...O hydrogen bonds with the benzoyl O atom of the ylide species. These structures are the first reported examples of co-crystals containing non-protonated BPPY.

Subtlety in the reactivity of a diketo phosphorus ylide towards mercuric halides: the unprecedented O-coordination of alpha-acetyl-alpha-benzoylmethylenetriphenylphosphorane to Hg(II).

The reactions of the title ylide with HgX2 (X = Cl, Br or I) lead to the regiospecific binding of the acetyl oxygen to soft Hg(II), producing a chloro complex with (2 + 2) coordination and isostructural dimeric bromo and iodo complexes containing halogen bridges with tetrahedral configurations around the metal centres.

N-(3-Chlorophenyl)-alpha-phenylnitrone: association with benzoic acid through hydrogen bonding

The identity of the title complex, C(13)H(10)ClNO.C(7)H(6)O(2), is confirmed to be a hydrogen-bonded adduct of benzoic acid and N-(3-chlorophenyl)-alpha-phenylnitrone. The two aromatic rings in the nitrone are trans about the C=N bond.