Synthesis and derivatization of naphthylcalcium halides as well as degradation in THF solution

The direct synthesis of 1-naphthyliodide and -bromide with calcium powder yields (thf)4Ca(Naph)I (1) and [(thf)3Ca(Naph)Br]2 (2), respectively. The metathesis reaction of 1 with KN(SiMe3)2 gives (thf)3Ca(Naph)–N(SiMe3)2 (3). In 2 and 3 very small Ca–C bond lengths of 252.8(4) and 251.4(6) pm, respectively, are observed. These compounds slowly decompose in THF solution via ether cleavage reactions. From this degradation, [(thf)4CaBr2] · naphthalene (4) crystallizes from THF solutions. Furthermore, decomposition of 1 in THF solution yields ethene and naphthalene whereas intermediate ethenolate undergoes subsequent degradation to an acetylide.

Graphical abstractThe direct synthesis of calcium powder with naphthylbromide yields [(thf)3Ca(Naph)Br]2 with bridging bromide anions whereas naphthylchloride shows no reactivity towards calcium. The bulky N(SiMe3)2 ligand leads to monomeric (thf)3Ca(Naph)–N(SiMe3) with strong agostic bonds between calcium and one trimethylsilyl group.Figure optionsDownload full-size imageDownload as PowerPoint slide