Synthesis, transition metal chemistry and catalytic reactions of ferrocenylbis(phosphonite), [Fe{C5H4P(OC6H3(OMe-o)(C3H5-p))2}2]

Abstract

The new metalloligand ferrocenylbis(phosphonite), [Fe(C₅H₄PR₂)₂ (R = OC₆H₃(OMe-o)(C₃H₅-p))], (2), is synthesized by the reaction of bis(dichlorophosphino)ferrocene Fe(C₅H₄PCl₂)₂ (1) with 4-allyl-2-methoxyphenol. The reactions of 2 with H₂O₂ and elemental sulfur or selenium afforded bischalcogenides, [Fe{C₅H₄P(E)(OC₆H₃(OMe-o)(C₃H₅-p))₂}₂] (3, E = O; 4, E = S; 5, E = Se), in good yield. The bis(phosphonite) reacts with group 6 metal carbonyls and group 10 metal dichloride precursors to produce the chelate complexes [{M(CO)₄}Fe{C₅H₄P(OC₆H₃(OMe-o)(C₃H₅-p))₂}₂}] (6, M = Mo; 7, M = W) and [(MCl₂)Fe{C₅H₄P(OC₆H₃(OMe-o)(C₃H₅-p))₂}₂] (8, M = Pd; 9, M = Pt). The palladium(II) complex [(PdCl₂)Fe{C₅H₄P(OC₆H₃(OMe-o)(C₃H₅-p))₂}₂] (8) is an efficient catalyst for the Suzuki–Miyaura cross-coupling reactions (TON up to 1.5 × 10⁵). The reaction of 2 with one equivalent of [RuCl₂(η⁶-p-cymene)]₂ yielded the binuclear complex [{Ru₂Cl₄(η⁶-p-cymene)₂}Fe{C₅H₄P(OC₆H₃(OMe-o)(C₃H₅-p))₂}₂] (12) in good yield. Treatment of 2 with copper chloride in a 1 : 1 or 1 : 2 molar ratio resulted in the formation of a binuclear complex, [{(CuCl)Fe{C₅H₄P(OC₆H₃(OMe-o)(C₃H₅-p))₂}₂}₂] (13), whereas a similar reaction of 2 with CuBr and CuI in a 1 : 2 or 1 : 2.5 molar ratio yielded the novel butterfly-like deca-nuclear complexes [Cu₅(μ-X)₅{Fe{C₅H₄P(OC₆H₃(OMe-o)(C₃H₅-p))₂}₂}₂]₂ (14, X = Br; 15, X = I). The reaction of 2 with two equivalents of [AuCl(SMe₂)] afforded the digold complex [(AuCl)₂Fe{C₅H₄P(OC₆H₃(OMe-o)(C₃H₅-p))₂}₂] (16), with the ligand exhibiting bridged-bidentate mode of coordination. Additionally, some complexes were studied by cyclic voltammetry. The crystal structures of complexes 8, 9, 12, 15 and 16 were determined using X-ray diffraction studies.