Preparation and Properties of Cyclopentadienyl Ruthenocenium Complexes with 1,2-Disubstituted Benzene Ligands: Competition between Chelate Coordination and Sandwich Coordination

The reactions of [CpRu­(NCMe)3]+ and 1,2-disubstituted
benzene ligands (L) bearing donor substituents were examined to investigate
the consequence of competing coordination modes. 1,2-C6H4(OMe)2 and 1,2-C6H4(SMe)­(OMe) produce [CpRu­(η6-L)]+-type
sandwich complexes with a η6 coordination mode, whereas
1,2-C6H4(SMe)2 forms the chelate
complex [CpRu­(κ2-L)­(NCMe)]+, due to the
coordination ability of the donor atoms. 1,2-C6H4(NMe2)2 and 1,2-C6H4(SMe)­(NMe2) produce the sandwich complexes or the chelate complexes
([CpRu­(κ2-L)­(NCMe)n]+; n = 0 or 1) depending on the reaction conditions.
The chelate complexes are the kinetic products and are thermally transformed
into the sandwich complexes in solution. The hexafluorophosphate (PF6) and bis­(trifluoromethylsulfonyl)­amide (Tf2N)
salts were isolated, and their thermal properties were investigated.
The Tf2N salts of the sandwich complexes are room-temperature
ionic liquids. The molecular structures were determined crystallographically.