Cobalt and chromium compounds of the composition [M(chxn) 3 ]Cl 3 (chxn ~trans-1,2-diaminocyclohexane) have been used as building blocks to synthesize ternary salts. Chirality of the cations allows control of the nature of the products. Joint crystallisation of Co(III) and Cr(III) complexes of the same configuration, i.e. both derived from either the same enantiomer or the racemate of the chiral chelating ligand, results in either homochiral or heterochiral solid solutions. Complex salts [M(rac-chxn) 3 ]Cl 3 ?H 2 O (M ~Co, Cr) crystallise in the tetragonal racemic space group I4 ¯2d. The preferred formation of this heterochiral structure offers the oppurtunity to synthesize an ordered solid of predictable geometry via the quasi-racemate approach: when Co(III) and Cr(III) cationic complexes of opposite chirality are cocrystallised, no solid solutions but a well-ordered ternary salt is obtained. X-Ray diffraction reveals a t 2 group-subgroup relationship between the racemic parent structure and the mixed crystals. The latter crystallise in the orthorhombic space group I2 1 2 1 2 1 with lattice parameters reflecting the different size requirements of trivalent cobalt and chromium cations.

Square planar complexes of the type [2-(1-aminoethyl)phenyl-kappa(2)C(1),N]chloro(py-kappaN)palladium(II)(py = pyridine derivative) have been prepared by cyclopalladation of 1-phenylethylamine. When opposite enantiomers of the chiral amine and different pyridine ligands were coordinated to the metal, quasiracemic complexes were obtained. The racemisation speed of solutions containing equimolar amounts of such quasiracemic complexes was used to test the compounds for inertness: slow ligand exchange was found for methylated pyridines. Enantiomerically pure complexes of opposite chirality with the electron rich ligands 2,6-collidine and 2,4,6-lutidine were successfully cocrystallised: they form a well-ordered binary solid in which four independent molecules, two of each constituent, are related by pseudo symmetry operations. This quasiracemate as well as its components and the true racemates of the latter were characterised by single crystal X-ray diffraction. The heterochiral crystals, both the cocrystal as well as the racemates, show better space filling than the homochiral solids.

An improved synthesis of (R,R)‐ and (S,S)‐hexane‐2,5‐diol is presented. The (S,S)‐derivative was converted into a cyclic sulfate, which on treatment with NaPH2 in liquid ammonia ultimately gave the secondary (R,R)‐2,5‐dimethylphospholane. This phospholane can be introduced into the side chain of chiral tricarbonylchromium and ferrocene derivatives to give new bidentate ligands of the Josiphos and Daniphos type. Both the ferrocene‐ and tricarbonylchromium‐based diphosphanes have been characterized by X‐ray diffraction analysis. A discussion of their structural features is included. The new ligands were successfully applied to the enantioselective hydrogenation of itaconic acid esters. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

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s13.m42.o1 Structural manipulation of hydrogen-bonded networks -inclusion of metal centres and chromophores and response to loss of symmetry.