Synthesis and characterization of nickel(II) maltolate complexes containing ancillary bisphosphine ligands

Abstract

Cationic nickel(II) complexes containing chelating O,O′-donor maltolate or ethyl maltolate ligands in conjunction with bidentate bisphosphine ligands Ph₂P(CH₂) _n PPh₂ were prepared by a one-pot reaction starting from nickel(II) acetate, bisphosphine, maltol (or ethyl maltol), and trimethylamine, and isolated as their tetraphenylborate salts. An X-ray structure determination of [Ni(maltolate)(Ph₂PCH₂CH₂PPh₂)]BPh₄ shows that the maltolate ligand binds asymmetrically to the (slightly distorted) square-planar nickel(II) center. The simplicity of the synthetic method was extended to the synthesis of the known platinum(II) maltolate complex [Pt(maltolate)(PPh₃)₂]BPh₄ which was obtained in high purity.

Keywords:

• Nickel complexes
• Maltol complexes
• Phosphine ligands
• X-ray crystal structure

Acknowledgments

We thank the University of Waikato for financial support of this work, Julia Lin and Bevan Jarman for NMR spectra, and Dr Tania Groutso (University of Auckland) for collection of the X-ray data set.