(2,2‐Dibromovinyl)ferrocene as a Building Block for the Assembly of Heterodinuclear Complexes – Preparation of an σ‐Alkenylpalladium Complex and Dimetallic Dithioether Complexes

The oxidative addition of (2,2‐dibromovinyl)ferrocene [Br 2 C=C(H)–Fc] ( 1 ) to [Pd(PPh 3 ) 4 ] yields the heterodinuclear σ‐alkenyl complex trans ‐[{Pd(Br)(PPh 3 ) 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 = t Bu; 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 [PtCl 2 (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)}PtCl 2 ] ( 7a ), respectively. Metathesis of the fluxional compound 7a in the presence of NaI affords [Fc{C(S– p ‐tolyl)=C(H)(S– p ‐tolyl)}PtI 2 ] ( 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. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)