Synthesis and catalytic properties of palladium() complexes with P,π-chelating ferrocene phosphinoallyl ligands and their non-tethered analogues

• Published in: Dalton transactions : an international journal of inorganic chemistry 2024-05, Vol.53 (2), p.8722-8731
• Main Authors: Škoch, Karel, Antala, Jakub, Císa ová, Ivana, Št pni ka, Petr
• Format: Article
• Language: English
• Subjects: Acetates; Alcohols; Aliphatic amines; Catalysts; Chelation; Chemical synthesis; Cross coupling; Palladium; Phosphines; Structural analysis
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/d4dt00961d

Hybrid phosphines usually combine a phosphine moiety with another heteroatom secondary donor group in their structures while compounds equipped with hydrocarbyl π-donor moieties remain uncommon. This contribution reports the synthesis and structural characterization of the first P/π-allyl-chelating complexes that were obtained using the structurally flexible and redox-active ferrocene unit as the scaffold, viz . [PdCl(R 2 PfcCHCHCH 2 -η 3 :κ P )] ( 1 R ; R = Ph and cyclohexyl (Cy); fc = ferrocene-1,1′-diyl). These compounds were synthesized from the respective phosphinoferrocene carboxaldehydes R 2 PfcCHO via reaction with vinylmagnesium bromide to generate 1-(phosphinoferrocenyl)allyl alcohols, which were subsequently acetylated. The resulting allyl acetates reacted smoothly with [Pd 2 (dba) 3 ]/[Et 3 NH]Cl (dba = dibenzylideneacetone) to produce the target compounds. Complexes 1 R and their nontethered analogues [PdCl(η 3 -C 3 H 5 )(FcPR 2 -κ P )] ( 5 R ; Fc = ferrocenyl) were evaluated as pre-catalysts for the Pd-catalysed allylic amination of cinnamyl acetate with aliphatic amines and Suzuki-Miyaura-type cross-coupling of 4-tolylboronic acid with benzoyl chloride. In these reactions, better results were achieved with compounds 5 R (particularly with 5 Ph ), presumably because they form more stable LPd(0)-type catalysts. Palladium( ii ) complexes with P,η 3 -chelating phosphinoallyl ligands and their non-tethered analogues were prepared and tested in Pd-catalysed allylic amination and Suzuki-Miyaura reactions.