Thioether-functionalized ferrocenyl-bis(phosphonite), Fe{(C5H4)P(-OC10H6(micro-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=-OC10H6(micro-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-kappaP,kappaP}] (5) or cis-[MCl2{Fe(C5H4PR)2-kappaP,kappaP}] (6, M=PdII; 7, M=PtII), respectively. However, treatment of 4 with CuX (X=Cl, Br, and I) produces binuclear complexes, [Cu2(micro-X)2(MeCN){Fe(C5H4PR)2-kappaP,kappaP}] (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-kappaP,kappaP}] (11), whereas treatment with 2 equiv of AuCl(SMe2) produces the dinuclear gold complex [Au(Cl){Fe(C5H4PR)2-kappaP,kappaP}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 1.36x10(5)).