Crystal structure of 4,4'-bis(4-chloro-1-phenyl-3-methyl-5-pyrazolonyl).

have been prepared and applied for the separation of the platinum-group metals, such as Pt, Pd, Ir and Rh, or tervalent lanthanides via solvent extraction.1–4 They are able to extract most metal ions at a lower pH than a related compound, βdiketones. We tried to prepare a novel derivative with an ethoxy group as an electron-releasing substituent, 1-phenyl-3methyl-4-ethoxyacetyl-5-pyrazolone, to evaluate the substituent effects on the acyl groups.5 The reaction of pyrazolone with ethoxyacetic chloride was carried out under the ordinary conditions mentioned below. As shown in Fig. 1, however, the product which precipitated in the resulting solution was not our desired compound, the ethoxyacetyl derivative of pyrazolone (1 in Fig. 1), but a chlorinated dimer of pylazolone, 4,4′-bis(4chloro-1-phenyl-3-methyl-5-pyrazolonyl) (2 in Fig. 1). In this paper, we describe the preparation of the titled compound and its characterization by an X-ray structure determination. A 1,4-dioxane solution (300 cm3) of 1-phenyl-3-methyl-5pyrazolone (15.2 g, 0.087 mol) and ethoxyacetyl chloride (11.8 g, 0.096 mol) was refluxed for 2 h with calcium hydroxide (13.5 g, 0.18 mol) and cooled to room temperature. Dilute hydrochloric acid (ca. 2 M, 200 cm3) was added. The acidic aqueous solution was poured into chloroform (200 cm3). The resulting compound was extracted to chloroform and the chloroform solition was evaporated under reduced pressure. An oily solid remained and was allowed to stand for at least one month in the dark to obtained pale-yellow prismatic crystals. A yellow prismatic crystal of the titled compound having approximate dimensions of 0.35 × 0.20 × 0.20 mm was mounted in a glass capillary. The non-hydrogen atoms were refined anisotropically. Hydrogen atoms were included at the calculated positions, but not refined. Neutral atom scattering factors were taken from International Tables for X-ray Crystallography, Vol. IV. The values for anomalous dispersion effects and mass attenuation coefficients were taken from International Tables for Crystallography, Vol. C. Other crystal and experimental data are given in Table1. The molecular structure of the titled compound is shown in Fig. 2, together with the atomic labeling scheme. The final atomic parameters are given in Table 2. The selected bond distances and bond angles are listed in Tables 3 and 4, respectively. The molecule consists of two 4-chloro-1-phenyl3-methyl-5-pyrazol-4-yl moieties, which are structurally analogous. Both of the two five-membered rings are 353 ANALYTICAL SCIENCES FEBRUARY 2001, VOL. 17 2001 © The Japan Society for Analytical Chemistry