Synthesis of Two Isomeric Ferrocene Phosphanylcarboxylic Acids and their PdII Complexes with and without Auxiliary ortho‐Metalated C,E‐Ligands (E = N and S)

Abstract

Two homologous ferrocene phosphanylcarboxylic acids, viz., 1′‐[(diphenylphosphanyl)methyl]ferrocene‐1‐carboxylic acid (HL1) and [1′‐(diphenylphosphanyl)ferrocenyl]acetic acid (HL2), were synthesized and studied as ligands in PdII complexes. The addition of these hybrid donors to [PdCl2(MeCN)2] led to the bis‐phosphane complexes trans‐[PdCl2(HL1‐κP)2] and trans‐[PdCl2(HL2‐κP)2]. In contrast, the reactions of HL1 and HL2 with the PdII acetylacetonate (acac) complexes [(LYC)Pd(acac)], where LYC = 2‐[(dimethylamino‐κN)methyl]phenyl‐κC1 (LNC) and 2‐[(methylthio‐κS)methyl]phenyl‐κC1 (LSC), proceeded under proton transfer and replacement of the acac ligand, giving rise to O,P‐bridged phosphanylcarboxylate dimers [LYCPd(µ(P,O)‐L1)]2 and molecular chelates [LYCPd(L2‐κ2O,P)]2, respectively. The analogous reactions involving 1′‐(diphenylphosphanyl)‐1‐ferrocenecarboxylic acid (Hdpf) provided the macrocyclic tetramer [LNCPd(µ(P,O)‐dpf)]4 and the dimer [LSCPd(µ(P,O)‐dpf)]2. The reactions of HL1 with [Pd(acac)2] only led to an ill‐defined, insoluble material, whereas those with HL2 produced a separable mixture of the bis‐chelate complexes trans‐[Pd(L2‐κ2O,P)2], cis‐[Pd(L2‐κ2O,P)2], and [Pd(acac)(L2‐κ2O,P)].