Bis‐Anagostic Structures in N,N’‐Chelate Ligand Complexes of Palladium(II)

• Published in: European journal of inorganic chemistry Vol. 2022; no. 12
• Main Authors: Sajjad, M. Arif, Schwerdtfeger, Peter, Cai, Yichao, Waters, Joyce M., Harrison, John A., Nielson, Alastair J.
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 27-04-2022
• Subjects: Aromatic compounds; bis-Anagostic interactions; Coordination compounds; Crystallography; Cyclometallation reactions; C−H bond activation; Density functional theory; Hydrogen bonds; Inorganic chemistry; Ligands; Mathematical analysis; NMR spectroscopy; Oxygen atoms; Palladium; Planar structures; Spectrum analysis
• ISSN: 1434-1948; 1099-0682
• DOI: 10.1002/ejic.202200027

Reaction of N,N’‐dibenzylidene‐2,2‐dimethylpropylenediamine with Pd(OAc)2 produces essentially one product which NMR spectroscopy indicates has a bis‐anagostic structure. A density functional theory (DFT) calculation shows that in the square planar structure, both aromatic rings lie above the coordination plane with close approaches of two ortho‐C−H bond hydrogens to both the Pd centre and the two acetato ligand coordinating oxygen atoms. N,N’‐dibenzylideneethylenediamine reacts with Pd(OAc)2 similarly where a bis‐anagostic structure is indicated by NMR spectroscopy and a DFT calculation shows an energy preference for an above plane positioning of the two aromatic rings. N,N,N’,N’‐tetrabenzylethylenediamine reacts with Pd(OAc)2 to give a structure which X‐ray crystallography shows two benzyl phenyl groups lie above and below the coordination plane respectively.
Chelating dibenzaldimine ligands on coordination to Pd(OAc)2 give 1H NMR spectra which indicate bis‐anagostic interactions of the aromatic ring ortho‐hydrogens with the palladium centre. DFT calculations show that in the solid state, both interactions occur above the coordination plane with one ortho‐hydrogen of each aromatic ring making close approaches to Pd and the adjacent acetato ligand coordinating oxygens.