Synthesis of a Palladium Dimer Supported by a C‑Bound Trifluoroacetonate Bridge Formed by Cleavage of a Hexafluoroacetylacetonate Ligand

• Published in: Organometallics Vol. 43; no. 17; pp. 1904 - 1911
• Main Authors: Byrne, Paul, Burgoon, Hugh, Koester, Jessica, Chen, Wei-Yuan, Ziegler, Christopher J., Tuca, Emilian, DiLabio, Gino A., Rhodes, Larry F.
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 09.09.2024
• ISSN: 0276-7333; 1520-6041
• DOI: 10.1021/acs.organomet.4c00263

Palladium­(II) hexafluoroacetylacetonate (Pd­(Hfacac)2) is known to form adducts of bases, such as lutidine (2,6-dimethylpyridine). When treated with approximately 3 equiv of lutidine, Pd­(Hfacac)2 yields a 1:1 complex as reported in the literature, Pd­(O,O-Hfacac)­(C-Hfacac)­(lutidine), 1. However, when the amount of excess lutidine is increased, a new complex, 2, is formed. A single-crystal X-ray structure of 2 proves it is a rare example of a dimeric palladium complex containing two Pd­(Hfacac)­(lutidine) fragments bridged by a dianionic trifluoroacetonate ligand, μ-CHC­(O)­CF3. The formation of 2 is accompanied by a white precipitate determined to be a mixture of trans-Pd­(O2CCF3)2(lutidine)2 (3), confirming the fate of the missing trifluoroacetate fragment from the cleavage of the Hfacac ligand, and [lutidinium]­[Hfacac] (4). Subsequent experiments revealed the determinative role that water played in this reaction. The mechanism of cleavage of the Hfacac ligand was explored by DFT methods.