Metal complexes of [2n]cyclophanes and their mixed valence ions
The possibility of synthesizing one—dimensional, u—electron delocalized, polymers of [2]cyclophane_transition metal complexes has been explored by preparing model monomer units of selected [2]cyclophane— ruthenium complexes and examining their properties. Bis(6—hexamethyl— benzene)(n10_[24](l,2,4,5)cyclophane)diruthenium(o/II) bis(tetrafluoro— borate) (14) is found to be a Class II mixed—valence compound exhibiting an unusual two—electron intervalence transfer. The discovery of [2n]_ cyclophanes having three benzene decks undergoing simultaneous u—electron interaction raises the further possibility of synthesizing two—dimensional, 6 666 network polymers. Tris(0 —hexamethylbenzene)(0 : : —[23](l,4)cyclophane— l,9,17—triene)triruthenium(II) tris(tetrafluoroborate) (19) has been prepared and the properties of its mixed—valence ions have been examined. With the completion of syntheses of all twelve of the possible, symmetrically—bridged, [2]_ cyclophanes their physical and chemical properties, as well as their geometry, have been examined in detail (ref. 1). The outstanding characteristic of the [2 ]cyclophanes, as revealed particularly from photoelectron and ESR studies (ref. 2 and 3), is the interaction of the two aromatic decks to give one overall u—electron system. This u—electron delocal— ization over the whole of the molecule is also observed with multilayered [2nlcYclophanes (ref. 4), as in the, example of 1 having six benzene decks. Extending 1 to provide a polymer molecule (la) having one u—electron system delocalized over a great many benzene decks would be of much interest, although at present such a synthesis appears to be prohibitively difficult. An alternate approach to a u—electron delocalized [2 ]cyclophane polymer might be a polymer having monomer units of [2]cyclophane—transition metal complexes, as shown by 2. Such