Synthesis and characterization of mono- and bi-metallic derivatives of Groups 4 and 5 with 2,5-dimethoxy-1,4-benzoquinone

Abstract

The ligating properties of 2,5-dimethoxy-1,4-benzoquinone, C₈H₈O₄1 towards metallic Lewis acids and organometallics in low oxidation states has been investigated. The title compound reacts with Group 4 tetrahalides to give adducts of formula MCl₄(C₈H₈O₄) (M = Ti 4a; M = Zr 4b) and (TiCl₄)₂(C₈H₈O₄) 5. Moreover, bis-cyclopentadienyl derivatives of titanium(II) (TiCp₂L₂; L = CO, PMe₃) and vanadium(II) (VCp₂) react with 1 affording both 1 : 1 and 2 : 1 derivatives of general formula MCp₂(C₈H₈O₄) (M = Ti 10; M = V 7), (MCp₂)₂(C₈H₈O₄) (M = Ti 11; M = V 6). The molecular structure of 6 has been determined by X-ray diffraction showing the presence of bimetallic units, with two [VCp₂] fragments bonded to a quinonoid oxygen atom of a bridging 2,5-dimethoxy-1,4-benzenedialcoholato. The derivatives [(MCp₂)₂(C₈H₈O₄)][BPh₄]_n (M = Ti, V; n = 1 12a, b; n = 2 12c, d) have been prepared by oxidation of (MCp₂)₂(C₈H₈O₄) (M = Ti 11; M = V 6) with a stoichiometric amount of [FeCp₂][BPh₄]. The reaction of the vanadium derivative VCp₂(C₈H₈O₄) 7 with TiCl₄ affords the heterobimetallic compound VCp₂(C₈H₈O₄)TiCl₄8. The magnetic properties of the 1 : 1 and 2 : 1 species are reported.