Crystal engineering based on preferred mirror image recognition in square planar Pd(ii) complexes

Unexpected solids from enantiopure cationic palladium complexes and racemic anions: A structural study of chiral non-discrimination

“…One might perhaps argue that our cations are ''not very chiral'' as their enantiomers ''only'' differ in the orientation of the methyl substituent in the cyclopalladated amine. However, in the organopalladium residues presented in this work as well as in a number of quasiracemic crystals which were synthesized in an entirely different context [27,28] and contain neutral molecules with related ligands, the assignment of chirality was always unambiguous, and the difference between the enantiomers proved sufficient to ensure ordered structures.…”

(S)-[2-(1-Aminoethyl)phenyl]chloro(3-chloropyridine)palladium(II) acetone 0.25-solvate

“…The mean planes through the atoms directly bonded to palladium and the heteroaromatic ring subtend a dihedral angle which is quite variable, with values of 57.51 (13), 52.47 (12), 53.14 (12) and 66.86 (12) . The large number of symmetrically independent residues per asymmetric unit indicates inefficient crystal packing in the complex; indeed, the overall space filling amounts to only 68.4%, which is low by comparison with chemically related complexes (Calmuschi, Alesi & Englert, 2004;Calmuschi & Englert, 2005). Attempts to cocrystallize this compound with related compounds of opposite chirality have, to date, resulted only in disordered binary crystal structures.…”

One of the most complex “small molecule structures” ever reported: 16 independent molecules in the asymmetric unit for an ortho-palladated primary amine

“…[2][3][4][5][6] Ortho-palladated primary amines have been made generally accessible by Vicente et al 7 and have proven suitable building blocks for this crystal engineering purpose. 8,9 In the context of these studies, we have prepared a variety of organopalladium compounds (see ESI).w [10][11][12][13][14][15][16][17][18][19][20][21] All complexes of this kind are unspectacular with respect to their content of the asymmetric unit. Z 0 , the number of independent molecules, varies between 1 and 4.…”

“…Compounds 1 and 2 were synthesized according to published procedures. [7][8][9] Suitable crystals of all compounds were obtained by slow evaporation of the solvent at room temperature over periods ranging from 10 days to 3 weeks. Solvents: MeOH/H 2 O = (1/1) for 1, acetonitrile for 1Á0.5 MeCN and 2Á0.5 MeCN.…”

“…The overall packing coefficients for the three compounds amount to 66.4% (1), 67.7% (1Á0.5 MeCN) and 66.2% (2Á0.5 MeCN) and are in agreement with results obtained on related compounds. 8,9 We do not claim to fully understand the driving force behind the exceptional crystal chemistry of 1. According to Kitaigorodskii's close packing principle 38 and standard considerations concerning lattice energy, molecules arrange in the solid state in a way to maximize density and minimize free volume.…”