PREPARATION AND CRYSTAL-STRUCTURES OF THE CE(IV) BETA-DIKETONATES, [CE(TMHD)(4)] AND [CE(PMHD)(4)] (TMHD = 2,2,6,6-TETRAMETHYLHEPTANE-3,5-DIONATE AND PMHD = 1-PHENYL-5-METHYLHEXANE-1,3-DIONATE)

The cerium(IV) beta-diketonate compounds [Ce(beta-diketk)(4)] [where b eta-diket = tmhd (2,2,6,6-tetramethylheptane3-5-dionate) 1, pmhd (1-ph enyl-5-methylhexane-1,3-dionate) 2] were prepared by reacting cerium(I V) ammonium nitrate [CAN; Ce(NH4)(2)(NO3)(6)] with the respective Na(b eta-diket) compound in ethanol, and structurally characterized by sing le crystal X-ray diffraction. Compound I crystallizes in the triclinic space group P (1) over bar with a = 12.472(4), b = 19.972(5), c 21.43 6(3) Angstrom, alpha = 97.05(7), beta = 90.16(2), gamma 106.55(3)degre es V = 5076(2) Angstrom(3), Z = 4, T = 150(2) K. Compound 2 crystalliz es in the monoclinic space group P2(1)/n. with a = 14.817(6), b = 17.1 23(6), c = 19.146(3) Angstrom, beta = 105.46(4)degrees, V = 4682(3) An gstrom(3), Z = 4, T = 150(2) K. Crystals of 1. contain two independent [Ce(tmhd)(4)] molecules, with four chelating tmhd ligands bonded to e ach metal in a distorted dodecahedral arrangement; the cerium atom in 2 is also bonded to four chelating pmhd ligands but in this case the c oordination geometry is closer to square antiprism. Both complexes are air and moisture stable. Sublimation studies reveal that 1 sublimes a lmost quantitatively, while 2 is comparatively involatile.