Synthesis of dichloro(phthalocyaninato)antimony(V) perchlorate, tetrafluoroborate, and hexafluorophosphate and electrochemical reinvestigation on the new complex salts

The titled new salts were synthesized by exchanging the unknown counter anion of [Sb(pc)Cl-2](+) salt (pc(2-) = phthalocyaninate, C32H16N82-), which was the first product of the reaction of phthalonitrile with antimony(III) trichloride, with perchlorate, tetrafluoroborate, and hexafluorophosphate. Elemental analytical data and infrared spectra of the new salts confirmed that these complexes are composed of one [Sb(pc)Cl-2](+) cation and one mononegative counter ion. The introduction of electrochemically inactive counter-anions exerted little effect on the electronic spectrum and the first and second pc-ring reduction potentials of the complex in dichloromethane, but has made it possible to observe the third and fourth reduction processes, which were not observed for the initial salt. Up to four successive reduction processes of a pc-ring were observed for the first time in a noncoordinating solvent. Although the (1) Delta(2)E(1/2) (half-wave potential interval between the first and second reduction processes; 0.45 V), and (3) Delta(4)E(1/2) (0.58 V) values for [Sb(pc)Cl-2](+) were typical of those for the known phthalocyanines, the (2) Delta(3)E(1/2) value (0.31 V) was much smaller. The anomaly in the spacing of the reduction processes for [Sb(pc)Cl-2](+) is discussed in terms of the lack of a significant Jahn-Teller distortion of the pc-ring upon reduction.