Synthesis of mononuclear, dinuctear and oligomeric rigid-rod acetylide complexes of rhodium, and the molecular structure of [Rh(PMe3)4(CC–p-C6H4–CC)Rh(PMe3)4]

Abstract

Reaction of two equivalents of [Rh(PMe₃)₄]Cl with HCC–X–CCH (X = none, p-C₆H₄, p-C₆F₄, p-C₆H₄-C₆H₄-p) yields the dinuclear acetylide bridged dications cis-cis-[Rh(PMe₃)₄(H)(CC–X–CC)Rh(PMe₃)₄(H)]²⁺[ Cl^–]₂, whereas reaction of [Rh(PMe₃)₄(Me)] with HCC–X–CCH (X =p-C₆H₄, p-C₆H₄–C₆H₄-p) yields neutral mononuclear, dinuclear or oligomeric rigid-rod complex mer-trans-[Rh(PMe₃)₃(H)(CC–X–CCH)₂], [Rh(PMe₃)₄(CC–X–CC)Rh(PMe₃)₄] or mer-trans-[–Rh(PMe₃)₃(H)–CC–X–CC–]_n, depending upon the stoichiometry employed (1 : 2, 2 :1, or 1 :1 respectively); the crystal and molecular structure of the dinuclear Rh^I complex [Rh(PMe₃)₄(CC–C₆H₄–CC)Rh(PMe₃)₄] has been determined by X-ray diffraction, and soluble rigid-rod oligomers have been isolated from reactions employing the PBuⁿ₃ ligand.