Fluxional Behavior of Palladium(II) and Platinum(II) Complexes Containing both a Metal–Aryl Bond and a Pyrazole-derived Ligand

• Published in: Bulletin of the Chemical Society of Japan Vol. 51; no. 11; pp. 3209 - 3212
• Main Authors: Onishi, Masayoshi, Sugimura, Koji, Hiraki, Katsuma
• Format: Journal Article
• Language: English
• Published: Tokyo The Chemical Society of Japan 01.11.1978; Chemical Society of Japan
• ISSN: 0009-2673; 1348-0634
• DOI: 10.1246/bcsj.51.3209

New (acetophenone oximato, 2-C,N)- and (benzophenone oximato, 2-C,N)palladium(II) complexes containing poly(1-pyrazolyl)borato ligand (BPz4 or HBPz3, Pz=1-pyrazolyl) or poly(1-pyrazolyl)methane (CPz4 or HCPz3) were prepared and investigated by means of 1H-NMR spectroscopy. For the BPz4 complexes, the tumbling motion of the BPz4 ligand averaged the environments of all four pyrazolyl groups to give spectroscopic equivalence above 65 °C, and was virtually frozen at ca. −9°C. With regard to the HBPz3, CPz4, and HCPz3 complexes, all pyrazolyl groups were equivalent at high temperature exhibiting stereochemical nonrigidity. The well-defined slow-exchange limiting spectra were not obtained at ca. −34 °C. In addition, new (acetophenone oximato, 2-C,N)platinum(II) complexes involving the BPz4 or HBPz3 ligand were prepared. The bidentate coordination of the BPz4 ligand in the BPz4 platinum(II) complex was stereochemically rigid in the range of 29 to 110 °C in DMSO-d6. Three pyrazolyl groups in the HBPz3 platinum(II) complex were equivalent at 85 °C in DMSO-d6, while the fluxional motion was fairly restricted at room temperature.