Synthesis of chromium(0) and molybdenum(0) bis (n6-arene) derivatives and their monoelectronic oxidation to [M(n6-arene)2]+ cations

M(¿6-arene)2 species (M = Cr, arene = 1,3,5-Me3C6H3; M = Mo, arene = 1,3,5-Me 3C6H3, 1,3,5-iPr3C 6H3), have been prepared by a modified Fischer-Hafner synthesis or by metal vapour techniques. The reaction of Cr(¿6-1, 3,5-Me3C6H3)2 with the fulvene derivatives pentacarbomethoxycyclopentadiene (pcmcpH), 1-benzoyl-6-hydroxy-6- phenylfulvene (dbcpH), or 1-benzoyl-3-nitro-6-hydroxy-6-phenylfulvene (dbncpH) proceeds with evolution of dihydrogen and formation of the ionic derivatives [Cr(¿6-1,3,5-Me3C6H3) 2][E], where E = pcmcp, dbcp, or dbncp. Mo(¿6-arene) 2 derivatives (arene = toluene, 1,3,5-Me3C 6H3, 1,3,5-iPr3C6H 3) are oxidized to [Mo(¿6-arene)2] + by pcmcpH. The crystal and molecular structures of [M(¿6-1,3,5-R3C6H3) 2][pcmcp] (M = Cr, R = Me; M = Mo, R = Me, iPr) have been solved by X-ray single crystal diffraction. © The Royal Society of Chemistry 2006.