Synthesis and Molecular Structure of trans‐[RhCl2(tBu2PPh)2]: a Rare Example of a Mononuclear Rhodium(II) Complex

During the reaction of [{Rh(μ‐Cl)(coe)2}2] (1) (coe = cis‐cyclooctene) with the tertiary phosphane tBu2PPh in a nitrogen atmosphere the square planar rhodium(II) complex trans‐[RhCl2(tBu2PPh)2] (2) was identified as a side product in moderate yield. 2 was synthesized in a defined manner in higher yields using a known procedure starting from [{Rh(μ‐Cl)(coe)2}2], tBu2PPh (molar ratio Rh:P of 1:2), and N‐chlorosuccinimide as the oxidizing agent in THF at room temperature. The molecular structure of 2 was determined by X‐ray crystallography. Additionally, to further confirm the molecular structure of trans‐[RhCl2(tBu2PPh)2], extensive DFT calculations were undertaken, which gave further evidence for its molecular structure. In contrast to the remarkable stability of 2 in the solid state, the investigation of solutions of this compound afforded hints at a dynamic equilibrium, which renders more difficult the collection of adequate NMR spectroscopic data for the title complex.