SYNTHESIS AND ESR-CHARACTERIZATION OF RADICAL-ANION COMPLEXES OF LANTHANUM - X-RAY CRYSTAL-STRUCTURE OF THE MIXED BIPY, BIPY(-1) COMPLEX OFLANTHANUM(III) [LAI2(BIPY)(BIPY)(DME)] - EVIDENCE FOR AN INTERLIGAND CHARGE-TRANSFER

The reaction of [LaI2(THF)(3)](2)[C10H8] with excess of 2,2'-bipyridin e (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 gen erates the mono-bipy complex [LaI2(bipy)(DME)(2)] (3). ESR and IR spec troscopic data show a fast shuttle electron transfer (SIET) between th e neutral and the radical anion of bipy in 1 and 2. The X-ray structur e 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 structu re 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 o xygen and four nitrogen atoms.