The crystal structure of bis(acetylacetonato)lead(II) and the structure of the acetylacetone solvated lead(II) ion in solution have been determined by single-crystal X-ray diffraction and large-angle X-ray scattering (LAXS), respectively. The acetylacetone is deprotonated and acts as a bidentate anionic ligand (acac-) in the solid Pb(acac)2 compound. The lead(II) ion binds four oxygen atoms strongly in a nearly flat pyramidal configuration with Pb-O bond lengths in the range 2.32-2.37 A, and additionally three oxygens from neighboring complexes at 3.01-3.26 A. Acetylacetone acts as a solvent (Hacac) at dissolution of lead(II) trifluoromethanesulfonate forming a pentasolvate with a mean Pb-O bond distance of 2.724(5) A. The 6s2 lone electron pair on the lead(II) ion becomes stereochemically active in the crystalline acetylacetonate complex, while it is inactive in the solvate in solution. The solution was also analysed using IR and 1H NMR spectroscopy.

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Crystal structures of 3,3,5,5-tetramethylglutarimide [3,3,5,5-tetramethylazacyclohexane-2,6-dione] (8) and the product of its reaction with phenyllithium, 2-hydroxy-2-phenyl-3,3,5,5-tetramethyl-6-piperidone (9), have been determined by X-ray structural methods [(8), monoclinic, P21/c, a = 7.715 (2), b = 11.136 (2), c = 11.707 (2) Å, \beta = 105.63 (3)°; (9), triclinic, P\overline 1, a = 6.1685 (6), b = 11.1475 (10), c = 11.526 (2) Å, \alpha = 117.100 (10), \beta = 103.390(10), \gamma = 91.288 (7)°]. Molecular structures of three different glutarimides are discussed. Their energy optimal structures were determined with the use of ab initio calculations. The results of crystallographic and theoretical studies show that the conformational changes in glutarimide introduced by substitution with methyl groups resulted in electron-charge distribution changes. These differences in charge distribution are the reason for the observed variation in yields of the reaction of glutarimides with phenyllithium.

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