Synthesis and reactions of heterodinuclear organopalladium complex having an unsymmetrical PN ligand

Novel heterodinuclear organopalladium complexes having an unsymmetrical PN ligand (Et2NC2H4PPh2-κ2N,P)RPd–MLn (MLn = Co(CO)4; R = Me (2a), Ph (2b), MLn = MoCp(CO)3; R = Ph (3b)) are synthesized by metathetical reactions of PdRX(Et2NC2H4PPh2-κ2N,P) (X = I, NO3) with Na+[MLn]−. Reversible dissociation of the Pd–N bond in 3b is revealed by variable temperature NMR studies. Reactions of 2a and 2b with CO yield corresponding acyl complexes (Et2NC2H4PPh2-κ2N,P)(RCO)Pd–Co(CO)4 (R = Me (5a), Ph (5b)). Rate of CO insertion for 2a and 2b is significantly faster than those for mononuclear methylpalladium complex, PdMeI(Et2NC2H4PPh2-κ2N,P) (1a), and methylpalladium–cobalt complex with a 1,2-bis(diphenylphosphino)ethane (dppe) ligand, (dppe-κ2P,P′)MePd–Co(CO)4 (6a). 5a smoothly reacts with nucleophiles such as diethylamine, methanol and benzenethiol to give corresponding amide, ester and thioester, respectively. These reactions of 5a are also significantly faster than those of corresponding mononuclear analogues and the similar heterodinuclear complexes with symmetrical bidentate ligands such as 1,2-bis(diphenylphosphino)ethane or N,N,N′,N′-tetramethylethylenediamine ligand.

Graphical abstractReactions of novel heterodinuclear organopalladium–cobalt complexes having an unsymmetrical PN ligand (Et2NC2H4PPh2-κ2N,P)RPd–MLn (MLn = Co(CO)4; R = Me, Ph) with CO yield corresponding acyl complexes (Et2NC2H4PPh2-κ2N,P)(RCO)Pd–Co(CO)4 (R = Me, Ph). Rate of CO insertion was significantly faster than those for mononuclear methylpalladium complex, PdMeI(Et2NC2H4PPh2-κ2N,P) and methylpalladium–cobalt complex with a 1,2-bis(diphenylphosphino)ethane (dppe) ligand, (dppe-κ2P,P′)MePd–Co(CO)4.Figure optionsDownload full-size imageDownload as PowerPoint slide