Aryl and aryne complexes of chromium, molybdenum, and tungsten. X-Ray crystal structures of [Cr(2-MeC6H4)(µ-2-MeC6H4)(PMe3)]2, Mo(η2-2-MeC6H3)(2-MeC6H4)2(PMe2Ph)2, and W(η2-2,5-Me2C6H2)(2,5-Me2C6H3)2-(PMe3)2

Abstract

The interaction of CrCl₃(thf)₃(thf = tetrahydrofuran) and 2-methylphenyl-lithium gives the chromium(IV) tetra-aryl Cr(2-MeC₆H₄)₄, which reacts with PMe₃ to give the dimeric chromium(II) complex [Cr(2-MeC₆H₄)(µ-2-MeC₆H₄)(PMe₃)]₂ as a minor product along with Cr(2-MeC₆H₄)₂(PMe₃)₂. Both can be made also by arylation of Cr₂(O₂CMe)₄ in the presence of PMe₃. The interaction of W(OPh)₆ and the 2-methylphenyl and 2,5-dimethylphenyl Grignard reagents gives the corresponding tungsten(IV) tetra-aryls. The interaction of PMe₂Ph and Mo(2-MeC₆H₄)₄ and of PMe₃ with W(2,5-Me₂C₆H₃)₄ gives, respectively, the aryne complexes Mo(η²-2-MeC₆H₃)(2-MeC₆H₄)₂(PMe₂Ph)₂ and W(η²-2,5-Me₂C₆H₂)(2,5-Me₂C₆H₃)₂(PMe₃)₂ whose X-ray structures indicate that they are best formulated as having metallacyclopropene rings. Spectroscopic and electrochemical data are given and X-ray crystal structures of three compounds are reported.