Synthesis of Two Isomeric Ferrocene Phosphanylcarboxylic Acids and their Pd^II Complexes with and without Auxiliary <i>ortho</i>‐Metalated C,E‐Ligands (E = N and S)

Abstract

Two homologous ferrocene phosphanylcarboxylic acids, viz., 1′‐[(diphenylphosphanyl)methyl]ferrocene‐1‐carboxylic acid ( HL 1 ) and [1′‐(diphenylphosphanyl)ferrocenyl]acetic acid ( HL 2 ), were synthesized and studied as ligands in Pd II complexes. The addition of these hybrid donors to [PdCl 2 (MeCN) 2 ] led to the bis‐phosphane complexes trans ‐[PdCl 2 ( HL 1 ‐κ P ) 2 ] and trans ‐[PdCl 2 ( HL 2 ‐κ P ) 2 ]. In contrast, the reactions of HL 1 and HL 2 with the Pd II acetylacetonate (acac) complexes [(L YC )Pd(acac)], where L YC = 2‐[(dimethylamino‐κ N )methyl]phenyl‐κ C 1 (L NC ) and 2‐[(methylthio‐κ S )methyl]phenyl‐κ C 1 (L SC ), proceeded under proton transfer and replacement of the acac ligand, giving rise to O,P‐bridged phosphanylcarboxylate dimers [L YC Pd(µ(P,O)‐ L 1 )] 2 and molecular chelates [L YC Pd( L 2 ‐κ 2 O , P )] 2 , respectively. The analogous reactions involving 1′‐(diphenylphosphanyl)‐1‐ferrocenecarboxylic acid (Hdpf) provided the macrocyclic tetramer [L NC Pd(µ(P,O)‐dpf)] 4 and the dimer [L SC Pd(µ(P,O)‐dpf)] 2 . The reactions of HL 1 with [Pd(acac) 2 ] only led to an ill‐defined, insoluble material, whereas those with HL 2 produced a separable mixture of the bis‐chelate complexes trans ‐[Pd( L 2 ‐κ 2 O , P ) 2 ], cis ‐[Pd( L 2 ‐κ 2 O , P ) 2 ], and [Pd(acac)( L 2 ‐κ 2 O , P )].