Crystalline samples of rare earth carbodiimides were synthesized by solid-state metathesis reactions of rare earth trichlorides with lithium cyanamide in sealed silica ampules. Two distinct structures were determined by single-crystal X-ray diffraction. The structure determined for Sm2(CN2)3 [C2/m, Z = 2, a = 14.534(2) A, b = 3.8880(8) A, c = 5.2691(9) A, beta = 95.96(2) degrees , R1 = 0.0267, and wR2 = 0.0667] was assigned for RE2(CN2)3 compounds with RE = Y, Pr, Nd, Sm, Gd, Tb, Dy, Ho, and Er, and the structure determined for Lu2(CN2)3 [R32, Z = 3, a = 6.2732(8) A, c = 14.681(2) A, R1 = 0.0208, and wR2 = 0.0526] was assigned for the smallest rare earth ions with RE = Tm, Yb, and Lu by powder X-ray diffraction. Both types of crystal structures are characterized by layers of [NCN](2-) ions whose arrangements can be derived from the motif of a closest packed layer of sticks. These layers alternate with layers of rare earth ions in a one-by-one sequence. Different tilting arrangements of the N-C-N-axes relative to the stacking directions (c) and different arrangements of RE3+ ions within metal atom layers account for the two distinct structures in which Sm3+ and Lu3+ ions adopt the coordination numbers 7 and 6, respectively.
A cyclic carbonyl ylide with a trans-annulated cyclopentane ring was generated by a Rh(2)(OAc)(4)-catalyzed reaction from a diazoketone precursor and trapped with allyl propiolate. The 1,3-dipolar cycloaddition led to the stereoselective formation of an oxygen-bridged polycycle. Via Curtius degradation, the cycloadduct was transformed to the ring skeleton typical of the sesquiterpene family of guaianolides.
Black single crystals of LiNb6Cl15 were obtained from reactions of Nb powder, NbCl5 and LiCl in sealed niobium tubes at 850°C. The heavy atom structure of LiNb6Cl15 (Ia3d (no. 230), Z = 16, a = 2055.5(2) pm at 100 K, R(F) = 0.028, R(F2) = 0.053) is isotypic with the structure of Ta6Cl15. The [Nb6Cl12]2+ clusters in the structure are three‐dimensionally interconnected via three additional Cla−a. These bridge all vertices of niobium clusters, consistent with [Nb6Cl12iCl 6/2a−a]− (the NbCla–aNb angles are 140°). At low temperatures the lithium ions are disordered over one‐third of sites (48 f), occupying cavities inside of two distorted corner‐sharing tetrahedra of chloride. These positions for lithium represent the narrowest sections of infinite channels in the structure built up by chloride. An increased lithium ion mobility is obtained above 170 K by 7Li‐NMR measurements.
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