Synthesis and ESR-characterization of radical anion complexes of lanthanum. X-ray crystal structure of the mixed bipy, bipy(-1) complex of lanthanum(III) [LaI2(bipy)(bipy)(DME)]: Evidence for an inter-ligand charge transfer

The reaction of [LaI2(THF)(3)](2)[C10H8] with excess of 2,2'-bipyridine (bipy) in DME or THF results in the formation of mixed radical anion ligand/neutral ligand complexes [LaI2(bipy(0))(bipy(-1))(L)(n)] with (L)(n)=(DME) (1) and (THF)(2) (2), whereas a reactant ratio of 1:2 generates the mono-bipy complex [LaI2(bipy)(DME)(2)] (3). ESR and IR spectroscopic data show a fast shuttle electron transfer (SIET) between the neutral and the radical anion of bipy in 1 and 2. The X-ray structure shows 1 to be monoclinic, space group P2/c, Z=2, with a=10.0320(12), b=9.7510(11), c=16.296(8) Angstrom, beta=90.43(2)degrees. The structure was refined to R=0.0360 for 2562 observed reflections (I >2 sigma(I)). It shows the lanthanum atom eight-coordinated by two iodine, two oxygen and four nitrogen atoms.