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The vast majority of racemic solutions of chiral compounds apparently crystallize at room temperature in non-Sohncke space groups as racemic crystals. However, kryptoracemic crystals composed of nearly enantiomeric pairs occasionally crystallize at room temperature, or appear as low-temperature phases, in Sohncke space groups. As a complement to the previously published catalog of organic kryptoracemates [Fábián & Brock (2010). Acta Cryst. B66, 94-103], 1412 chiral organometallic crystal structures have now been extracted from the Cambridge Structural Database and analyzed. 26 are listed herein as credible kryptoracemates. The possible influence of temperature is discussed, together with some problems in characterizing and classifying these structures.

The reaction of diphenylcyclopropenone with tetrakis(triphenylphosphine)platinum(O) is described, and the results of an X-ray crystallographic study of the product are reported.

The barriers to rotation of the aryl groups of m-nitrophenyladamantylpiperidine and m-nitrophenylcyclohexylpiperidine have been studied by variable-temperature NMR spectroscopy. NMR spectra of the free bases and salts of phenyladamantylpiperidine and phenylcyclohexylpiperidine (phencyclidine) and an X-ray crystal structure of the adamantane derivative verify the preferred conformations of these molecules in solution and the solid state. Force-field calculations provide additional information on the energetics of conformational processes in these molecules.