CRYSTAL AND MOLECULAR-STRUCTURES OF BIS(1,3-DI-TERT-BUTYLCYCLOPENTADIENYL)CERIUM CHLORIDE AND BOROHYDRIDE - 1ST EXAMPLE OF THE BRIDGING TETRADENTATE BH4-GROUP WITH 2 MU-3-HYDROGENS - MU-ETA-4-[(MU-3-H)2B(MU-2-H)2]

Interaction between CeCl3 and two equivalents of (C5H3Bu(t)2)Na leads to the complex [(eta-5-C5H3Bu(t)2)2Ce(mu-2-Cl)]2 (I). Crystals of I are rhombic, a = 13.032(3), b = 24.629(5), c = 17.044(3) angstrom, space group Pbnb, Z = 4, d = 1.630 g cm-3. Complex I reacts with one equivalent of LiBH4 to afford {(eta-5-C5H3Bu(t)2)2Ce[mu: eta-4-(eta-3-H)2B(mu-2-H)2]}2 (II) which is isostructural to I. Two BH4 groups in complex II are tetradentate and contain two mu-3- and two mu-2-bridging hydrogens. Cerium has a 20e environment.