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(C 5 H 4 PR) 2 (4, R = -OC 10 H 6 (μ-S)C 10 H 6 O-) 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 -κP,κP}] (5) or cis-[MCl2{Fe(C5H4PR) 2 -κP,κP}] (6, M = Pd"; 7, M = Pt"), respectively. However, treatment of 4 with CuX (X = Cl, Br, and I) produces binuclear complexes, [Cu 2 (μ-X)2(MeCN){Fe(C5H4-PR) 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(PPh 3 )OTf gives the mononuclear chelate complex [Ag(OTf)PPh3{Fe(C5H4PR) 2 -κ-P,κP}] (11), whereas treatment with 2 equiv of AuCl(SMe 2 ) 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 x 10 5 ).