Synthesis and characterization of chromium(I) bis(η6-toluene) derivatives containing sterically demanding anions

The reaction of Cr(η6-CH3C6H5)2 with 1-benzoyl-6-hydroxy-6-phenyl fulvene, dbcpH, and with pentakis (methoxycarbonyl)cyclopentadiene, pcmcpH, proceeds with evolution of dihydrogen and the formation of the ionic derivatives [Cr(η6-CH3C6H5)2][X] ([X]− = 1,2-dibenzoylcyclopentadienyl, [dbcp]−, pentakis (methoxycarbonyl)cyclopentadienyl, [pcmcp]−), which have been characterized by IR and EPR spectroscopies, X-ray diffraction and electrochemical techniques. The sterically demanding anions do not affect the structural and electronic properties of the View the MathML sourceCr(η6-CH3C6H5)2+ cations in solution but strongly influence crystal packing. In fact, a rare cis-eclipsed conformation of the toluene rings is found for [Cr(η6-CH3C6H5)2][dbcp] · THF, whereas two independent complexes are observed in the unit cell of [Cr(η6-CH3C6H5)2][pcmcp], one with toluene rings in a cis-eclipsed conformation and the other in a staggered conformation (projections of methyl groups form an angle of 151°).