Hexaethylbenzene complexes of ruthenium and manganese — X-ray crystal structures and NMR spectra of [(HEB)2Ru2(µ-Cl)3][C5(CO2Me)5], [(HEB)Ru(H2O)3][BF4]2, (HEB)RuCl2[P(OMe)3], trans-RuCl2(PMe3)4, and (HEB)Mn(CO)2Br

Abstract

Hexaethylbenzene (HEB) and [(p-cymene)RuCl2]2 react in the melt to yield [(HEB)RuCl2]2 (6), the NMR spectra of which reveal the presence of [(HEB)2Ru2(µ-Cl)3]Cl in solution. In [(HEB)2Ru2(µ-Cl)3][C5(CO2Me)5] (7), the cation has D3h symmetry with alternating proximal and distal ethyl groups. Bridge cleavage of 6 with trimethyl phosphite or with trimethylphosphine gives (HEB)RuCl2[P(OMe)3] (9) or (HEB)RuCl2(PMe3) (10), respectively. The latter reaction also yields RuCl2(Me3P)4 (11), whose structure represents a relatively rare example of a crystallographically characterized trans isomer of this type. In 9, five of the ethyl ligands are distal, whereas in 10 all six substituents are distal. Attempts to prepare the sandwich dication [(HEB)2Ru]2+ gave instead [(HEB)Ru(H2O)3](BF4)2 (8), whose NMR and X-ray data reveal the 1,3,5-distal–2,4,6-proximal arrangement of ethyls both in the solid state and in solution. (HEB)Mn(CO)2Br (13) likewise adopts the 1,3,5-distal–2,4,6-proximal structure in the solid state but, surprisingly, there is no evidence for slowed ethyl rotation in solution.Key words: hexaethylbenzene conformations, hindered rotations, crystallography, NMR, ruthenium, manganese.