Thioether-functionalized ferrocenyl-bis(phosphonite), Fe{(C5H4)P(-OC10H6(μ-S)C10H6O-)}2:: Synthesis, coordination behavior, and application in suzuki-miyaura cross-coupling reactions

The thioether-functionalized metalloligand ferrocenyl-bis(phosphonite), Fe(C5H4PR)(2) (4, R = -OC(10)oH(6)(mu-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)(2)Cl](2) or M(COD)Cl-2 afforded the chelate complexes, cis-[Rh(CO)Cl{Fe(C5H4PR)(2)-kappa P,kappa P}] (5) or cis-[MCl2{Fe(C5H4PR)(2)-kappa P kappa P}] (6, M = Pd-II; 7, M = Pt-II), respectively. However, treatment of 4 with CuX (X = Cl, Br, and 1) produces binuclear complexes, [CU2(mu-X)(2)(MeCN){Fe(C5H4PR)(2)-kappa P,kappa P}] (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)-kappa P kappa P}] (11), whereas treatment with 2 equiv of AuCl(SMe2) produces the dinuclear gold complex [Au(Cl){Fe(C5H4PR)(2)-kappa P kappa P}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 x 10(5)).