The first osmium(II), ruthenium(II) and iron(II) complexes of [3_n]cyclophanes (n = 2-4): synthesis and electrochemical study

摘要

(#eta#~6-C_6H_6)(#eta#~6-[3_n]Cyclophane)Ru(II) [BF_4]_2 and corresponding Os(II) [PF_6]_2, as well as bis(#eta#~5-C_5H_5)(#eta#~6,#eta#~6-[3_n]cyclophane)Fe(II)Fe(II) [PF_6]_2 ([3_n]cyclophane = [3_2](1,4)cyclophane 2, [3_3](1,3,5)cyclophane 3, [3_4](1,2,3,5)cyclophane 4, [3_4](1,2,4,5)cyclophane 5) have been synthesized and characterized. The complexation shifts of the ~1H-NMR signals of the metal-bound aromatic protons (H_b) are ca. 0.5-0.7 and 0.1-0.4 ppm for Fe(II) and Ru(II) complexes, respectively, whereas those of Os(II) complexes are ca. -0.2-0.1 ppm. The complexation shifts of the ~(13)C-NMR signals of the tertiary aromatic carbons of the metal-bound benzene ring are ca. 39-42 and 45-50 ppm for Ru(II) and Os(II) complexes, respectively. Thus the ~1H- and ~(13)C-NMR chemical shifts of the metal-bound aromatic hydrogens and carbons are strongly influenced by the anisotropy effect of the metal. The Pu(II) complexes showed electrochemically reversible responses. In the case of Os(II) complexes, a well-defined cathodic peak was also observed, but the rising portion of the corresponding anodic peak was somewhat deviated from the ordinary CV profile. In both cases, the redox process was attributed to the two-electron one-step mechanism, M(II) <-> M(0) (M = Ru and Os). An analysis of the redox properties of the Ru(II) and Os(II) complexes suggested that the Os(II)[3_4](1,2,4,5)cyclophane complex would be the most suitable subunit of an anticipated one-dimensional organometallic polymer.