Stereoretentive Ligand Exchange Reactions of N‑Fused Porphyrin Ruthenium(II) Complexes

The ligand exchange reactions of the ruthenium­(II) complex of N-fused tetraphenylporphyrin, Ru­(NFp)­(CO)₂Cl (<b>2</b>), with various anions were investigated. The chloride ligand of the isomers <b>2a</b>–<b>c</b> was stereoretentively exchanged with bromide (Br^–), iodide (I^–), and acetate (AcO^–) anions in toluene at 100 °C, structures of which were confirmed by ¹H NMR as well as single crystal X-ray diffraction analysis. The silver (AgOAc, AgOTf) and boron (NaBPh₄) reagents also afforded the corresponding stereoretentive products. On the other hand, the reaction with NaBH₄ afforded the hydride complex Ru­(NFp)­(CO)₂H (<b>7</b>) with low stereospecificity, showing a higher reactivity of <b>2c</b> than other isomers. The ligand dissociation mechanism was proposed with the help of theoretical calculations on the plausible five-coordinated intermediates