Tris(4-methoxyphenyl)stibine

Abstract

The C 3 -symmetrical molecule, tris(4-methoxyphenyl)stibine, C 21 H 21 O 3 Sb, crystallizes with one third of the molecule in the asymmetric unit. Bond lengths and angles of the Sb-C bonds lie in between those of the isostructural homologues C 21 H 21 O 3 Bi and C 21 H 21 O 3 As. The formation of dimers via six weak C-HÁ Á Á interactions is considered. Structure descriptionThe title compound, C 21 H 21 O 3 Sb, exhibits perfect C 3 -symmetry with one third of the molecule in the asymmetric unit. To our surprise, the structure of the title compound (Fig. 1) is not reported in the database (CSD; Groom et al., 2016), although we regularly observe it as a side product in our synthesis of asymmetric sulfides (Bö hm et al., 2018). To fill the gap in the row of homologues of the type C 21 H 21 O 3 E, with E being an element of group 14, the title compound is reported herein. It is isostructural with the homologues C 21 H 21 O 3 Bi (Hé bert et al., 2016) and C 21 H 21 O 3 As (Sobolev & Belsky, 1981). The lighter homologue C 21 H 21 O 3 P (Allman et al. , 1986;Bruckmann et al., 1995) crystallizes in the space group P2 1 /c while the lightest homologue C 21 H 21 O 3 N is, so far, not known in the CSD. The Sb-C bond distance and C-Sb-C angle observed here, 2.148 (2) Å and 95.8 (1) , lie between those of the neighbouring isostructural As and Bi homologues. However, the Sb-C bond distance is closer to that of the Bi derivative with the Bi-C distances being 0.103 Å longer, and the As-C distance 0.175 Å shorter, than that observed for the title compound. No strong intermolecular interactions were observed, Fig. 2. The distances between the C1-C6 centroid and atoms C5 or C3 of the next molecules [3.814 (2) and 3.849 (2) Å , respectively] indicate weak C-HÁ Á Á interactions, Table 1 and Fig. 3. It is noteworthy that two molecules are connected by six of these weak C-HÁ Á Á interactions via C3, forming discrete dimeric units with the antimony atom facing outwards.