Structure and Thermal Stability of the Benzo-15-Crown-5 with Lanthanum (III) Bromide Complex.

The reaction of benzo-15-crown-5 (C14142005) ligand with La(NO3)3.7H20 in the presence of HBr has resulted in the production of an exotic sandwich complex, (LaC28H36Br401011â¢38d. The crystal system is triclinic with space group P1, a = 12.5834(14) A, b = 13.5816(16) A, c = 13.8403(16) A, a = 70.751(2)°, fl = 66.773(2)° and y = 67.631(2)0. The cation comprises of the lanthanum atom coordinated to two crowns via three oxygen atoms from each crown in a 7/3-sandwich fashion. The two phenyl groups of the crown are brorninated. The La-Ougand bond d lengths are between 2.857(7) and 2.949(7) A. The trianion (3Brf- is linear with BrâBr bond lengths of _ 2.518(2) and 2.560(2) A respectively. The molecule is stabilized by intermolecular interactions of the type CâHBr to form dimers and are arranged parallel to be face. Keywords: lanthanum, benzo-15-crown-5, hydrogen bonding, bromination, x-ray structur