Investigation and Application of Aryl Carbon-Halogen Bond Cleavage with Rhodium and Iridium Porphyrin Complexes.

摘要

This thesis focuses on the reaction scopes, mechanistic investigations and applications of base-promoted aryl carbon-halogen (Ar-X) bond cleavage with iridium and rhodium porphyrin complexes. This thesis is divided into four parts: (1) Ar-X (X = Cl, Br, I) bond cleavage with Rh(ttp)Cl; (2) competitive Ar-F and Ar-Cl bond cleavage with iridium and rhodium porphyrins; (3) fluorine substituent effect on the M-Ar (M = Ir, Rh) bond strength; and (4) synthesis of iridium porphyrin BODIPY complexes.;Part I describes the reaction scopes and mechanism of Ar-X (X = I, Br, Cl) bond cleavage with Rh(ttp)Cl (ttp = 5,10,15,20-tetratolylporphyrinato dianion). Under basic conditions, both electron-rich and electron-deficient ArX undergo Ar-X bond cleavage to give Rh(ttp)Ar in good yields. [special characters omitted].;The mechanistic investigations suggest that RhIII(ttp)Cl first undergoes ligand substitution by OH- to give Rh III(ttp)OH, which forms [RhII(ttp)]2 through reductive dimerization. RhII(ttp) radical, which is in equilibrium with [RhII(ttp)]2, cleaves the Ar-X (X = I, Br, Cl) bond through metalloradical ipso-substitution and gives RhIII(ttp)Ar and X radical. X radical recombines with another RhII(ttp) radical to generate RhIII(ttp)X, which gives back RhIII(ttp)OH through ligand substitution by OH -. [special characters omitted].;Part II describes the competitive Ar-F and Ar-X (X = Cl, Br) bond cleavage reactions of fluorochlorobenzenes with iridium and rhodium porphyrin complexes. Mechanistic studies suggest that M(por)- is the intermediate for the Ar-F bond cleavage while MII(por) is the intermediate for the Ar-X bond cleavage. By taking advantage of the difference in mechanisms of the Ar-F and Ar-X bond cleavages, the selectivity of bond cleavage can be controlled by varying the reaction conditions. The Ar-F bond cleavage is favored in a polar solvent with a stronger base at lower temperatures with M(por)- precursor, and the Ar-X bond cleavage is favored under non-polar conditions with a weaker base and at higher temperatures. [special characters omitted].;Part III describes the meta-fluorine substituent effect on strengthening the M-Ar (M = Ir, Rh) bond of M(ttp)ArF. M(ttp)Ar F with meta-fluorine substituent are the most stable isomers among the isomeric Ar-H bond cleavage products. At 250 °C for 30 days, the three isomers of Ir(ttp)C6H4F reached an equilibrium with o : m : p = 0 : 5 : 1. The theoretical calculations also suggest that Ir(ttp)(3-fluorophenyl) is of lower energy than Ir(ttp)(2-fluorophenyl) and Ir(ttp)(4-fluorophenyl). The ortho-fluorine substituent exhibits steric effect which weakens the M-Ar bond. The meta-fluorine, which is more electron-withdrawing than para-fluorine, enhances the polarity of the M-C( ipso) bond and thus strengthens the M-Ar bond. [special characters omitted].;Part IV describes the application of Ar-I bond cleavage with Ir(ttp)(CO)Cl in synthesizing iridium porphyrin boron-dipyrromethene (BODIPY) complexes, which are potential photosensitizers for biological imaging and photodynamic therapy. The clinically interested iridium porphyrin BODIPY complexes have been prepared by a radical process of metalloradical with BODIPY. [special characters omitted].