The thioether-functionalized metalloligand ferrocenyl-bis(phosphonite), Fe(C5H4PR)2 (4, R = −OC10H6(μ-S)C10H6O−) is synthesized in three steps starting from ferrocene, and its coordination behavior toward various transition-metal derivatives is described. The reactions of 4 with [Rh(CO)2Cl]2 or M(COD)Cl2 afforded the chelate complexes, cis-[Rh(CO)Cl{Fe(C5H4PR)2-κP,κP}] (5) or cis-[MCl2{Fe(C5H4PR)2-κP,κP}] (6, M = PdII; 7, M = PtII), respectively. However, treatment of 4 with CuX (X = Cl, Br, and I) produces binuclear complexes, [Cu2(μ-X)2(MeCN){Fe(C5H4PR)2-κP,κP}] (8, X = Cl; 9, X = Br; 10, X = I) where the sulfur atom on one side of the ligand is involved in a weak interaction with the copper center. Reaction of 4 with 1 equiv of Ag(PPh3)OTf gives the mononuclear chelate complex [Ag(OTf)PPh3{Fe(C5H4PR)2-κP,κP}] (11), whereas treatment with 2 equiv of AuCl(SMe2) produces the dinuclear gold complex [Au(Cl){Fe(C5H4PR)2-κP,κP}Au(Cl)] (12). The crystal structures of 10 and 12 are reported, where a strong metallophilic interaction is observed between the closed-shell metal centers. The palladium complex 6 catalyzes the Suzuki cross-coupling reactions of aryl bromides with phenylboronic acid with excellent turnover numbers (TON up to 1.36 × 105).

Council of Scientific & Industrial Research (CSIR) - India