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)2 Cl (2), with various anions were investigated. The chloride ligand of the isomers 2a-c was stereoretentively exchanged with bromide (Br- ), iodide (I- ), and acetate (AcO- ) anions in toluene at 100 °C, structures of which were confirmed by1 H 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)2 H (7) with low stereospecificity, showing a higher reactivity of 2c than other isomers. The ligand dissociation mechanism was proposed with the help of theoretical calculations on the plausible five-coordinated intermediates.