Résumé
The oxidative addition of (2,2-dibromovinyl)ferrocene [Br2C=C(H)–Fc] (1) to [Pd(PPh3)4] yields the heterodinuclear σ-alkenyl complex trans-[{Pd(Br)(PPh3)2}–C(Br)=C(H)–Fc] (2). Nucleophilic attack of sodium thiolates on 1 unexpectedly affords the vinyl thioether derivatives (Z)-[(RS)(H)C=C(H)–Fc] (4a: R = Ph; 4b: R = tBu; 4c: R = Et). Complexes 4a and 4c can also be prepared by addition of NaSR across the triple bond of Fc–C≡C–H (3). Addition of an excess of NaSR to 1 affords the dithioether derivatives (Z)-[(RS)(H)C=C(SR)–Fc] (5a: R = Ph; 5b: R = p-tolyl; 5c: R = Et). An addition/elimination sequence is suggested to account for this surprising result. The yield of 5c is very low due to a competing formation of ethynylferrocene (3). Reaction of 5b with [Re(thf)(CO)3(μ-Br)]2 and [PtCl2(PhCN)2] leads to the heterodinuclear chelate complexes [Fc{C(S–p-tolyl)=C(H)(S–p-tolyl)}Re(Br)(CO)3] (6) and [Fc{C(S–p-tolyl)=C(H)(S–p-tolyl)}PtCl2] (7a), respectively. Metathesis of the fluxional compound 7a in the presence of NaI affords [Fc{C(S–p-tolyl)=C(H)(S–p-tolyl)}PtI2] (7b). The electrochemical properties of some of these complexes have been studied by means of cyclic voltammetry, and the molecular structures of 1, 2, 3, 4b, 4c and 6 have been determined by X-ray diffraction.