SYNTHESIS, SPECTROSCOPY, AND CRYSTAL-STRUCTURE OF A NEW STABLE BISCYCLOPENTADIENYL URANIUM(IV) DICHLORIDE CONTAINING 2 C5H4-RINGS INTERLINKED BY A METAL-COORDINATED 2,6-BIS(METHYLENE)PYRIDYL UNIT

Reaction of the new disodium salt: Na2[2,6-C5H3N(CH2C5H4)2 (2; 2,6-C5H3N = 2,6-pyridyl) with UCl4 in THF affords the reddish-green, mononuclear Cp2U(IV)Cl2-derivative (Cp = eta-5-C,H5): mu-(2,6-CH2C5H3NCH2}(eta-5-C5H4)2U(IV)Cl2 (1). According to a single-crystal X-ray study, 1 involves a notably strong U-N bond (U-N(av): 2.62(1) angstrom) along with two nonequivalent Cl ligands (U-Cl: 2.615(3) and 2.636(3) angstrom). The low-temperature H-1 NMR spectrum of the paramagnetic complex is in full accord with the solid state structure 1. Up to room temperature, the dissolved molecules of 1 show no fluxionality on the NMR time scale, although the two CH2 proton resonances appear to undergo coalescence.