Naphthalene complexes. Part 1. Metal vapour preparation of bis(η6-naphthalene)chromium(0) and its arene replacement reactions
Bis(η6-naphthalene)chromium(0), formed in high yield from chromium atoms and naphthalene in solution at –80 °C, is a thermally stable but very reactive compound. Two-electron donor ligands displace one naphthalene ring [L = PF3, P(OMe)3, or PMe3] or both naphthalene rings (L = CO, CNBut, or CNC6H11) in rapid reactions at room temperature. The product [Cr(C10H8)(PMe3)3] is susceptible to further displacement of naphthalene by CO at 0 °C. The reaction of chromium atoms with 1,4-dimethylnaphthalene is stereospecific. More than 95% of the product is the isomer of [Cr(C10H8Me2)2] in which the unsubstituted ring is bonded to the metal. Bis(1-methylnaphthalene) chromium exists as a mixture of 10 isomers which can be distinguished on the basis of their 1H n.m.r. spectra.