Journal of the American Chemical Society, 1985

Note Added in Proof. We have recently found that W 4 ( p CSiMe3)2(OEt),4 crystallizes from hexane in a second monoclinic form. Crvstal data at -160 o c are as fo~~ows: a = 14.207 Data were corrected for absorption, although the correction may be poorly defined due to the very irregular shape of the fragment utilized. A final difference Fourier revealed several peaks of density 1.0 to 2.1 e/A3 within 1.0 A of the three metal atoms but was otherwise featureless.

Acta crystallographica, 1977

The structure of bis(q-cyclopentadienyl)-g-[(1,2,5-q : 1,4,5-q)-1,2-dimethyl-3-oxo-4,5-bis(trifluoromethyl)-1,4pentadiene-l,5-diyl]-dirhodium (Rh-Rh), (o-CsHs)2Rhz{/t-[(CH3CzCH3)CO(CF3CzCF3)]}, has been determined from 2161 diffractometer data and refined by least squares to R = 0.041. The compound is monoclinic, space group P2Jn, with a = 14.279 (5), b = 16-446 (6), c = 7.

Journal of Crystallographic and Spectroscopic Research, 1982

The crystal structure of [(775 -CsHs)2HfO]3"C6HsMe has shown that the compound is not isostructural with its zirconium analog. The title compound crystallizes in the orthorhombic space group Cmcm with well-refined parameters associated with the organometallic moiety and the toluene molecule, whereas [075 -C~Hs)2ZrO]3"C6HsMe has been reported to belong to the monoclinic space group P21/c with a badly disordered molecule of crystallization. The hafnium derivative exhibits unit cell constants a---12.322(3), b = 17.473(4), c = 17.836(4) A, and Z = 4 for De = 1.84 g cm -3 Full-matrix least-squares refinement gave a final R value of 0.062 for 1243 independent observed reflections. The trimer resides on a site of crystallographic mm symmetry. The 075 -CsHs)EHf units are bridged together by oxygen atoms at an average Hf-O distance ofL95(2) A.

Polyhedron, 1996

Abstraet-NdC13 reacted with C6H5CH2CsH4Na in the ratio 1:1 at-78'~C giving [C6H 5 CH2CsH4NdC12' nTHF], which then was reacted with CsHsK2/THF to yield the title complex [(CsHs)3(C6H5CH2CsH4)Nd2K(THF)3] (C6HsCH2CsH4 = benzylcyclopentadienyl). The crystal structure of the Nd complex was determined by X-ray diffraction and revealed that the benzyl group is coordinated to the potassium atom to form a new type of trinuclear complex [(~/s_ CsHs)Nd(#2-r/8-CsHsK(THF) (t/3-C6HsCH2-#2-/7 5-C5H4)Nd (THF)2(q 8-CsHs)].

Zeitschrift für Kristallographie - New Crystal Structures, 2002

Journal of Inorganic and Nuclear Chemistry, 1980

molar absorptivities in the visible region are greater than 167118]• For the iodide complex it is 1096 at 530nm. Finally, for the nickel heteropoly complex a band would be expected at approx. 400 nm for octahedral coordination and it would not be expected for tetrahedral coordination of the Ni(lI) ions[18]. The X-ray powder pattern of ammonium sodium nickel(ll)undecatungstogallate(Ill) was compared to a pattern of ammonium sodium undecatungstogallate(llI), (NH4)7Naz[H:GaO4WlIO36] • 15H20, which was taken on the same instrument at 26°C [21]. The crystallographic unit cell edges are essentially the same being 22.44 and 22.42 A, respectively. The line positions and intensities were also in excellent agreement, and there were no lines for those impossible combinations of h 2+k 2+12. Ammonium sodium nickel(ll)undecatungstogallate(lllt is thus a new isomorph of that series of heteropoly complex possessing Keggin-type anions [3, 7, 8]. Single-crystal X-ray structural work with ammonium sodium undecatungstogallate(lll)[10] and other of its isomorphs[3] have shown that the possible cubic system space group is Fm3m, F42m, F432, or F23. Each of these requires 8 units, with the characteristic four threefold axes of symmetry of a Keggin-type anion, in its crystallographic unit cell. Our experimental value of 8.15 for this parameter for ammonium sodium nickel(ll)undecatungstogallate(Ill) is thus in agreement•

Journal of Crystallographic and Spectroscopic Research, 1984

The crystal structure of (r/5-CsHs)2Hf(r/I-NC4H4)2 has been determined from X-ray data measured by counter methods. The title compound is is 9 with (r/5-CsHs)2Zr(r/1-NC4H4)2, and crystallizes in the monoclinic space group P2i/c (C~h, No. 14) with unit cell constants a = 9.605(3), b = 8.174(3), c = 19.487(4) A, 13 = 90.85(3) ~ and Z = 4 for Dc = 1.91 gcm -3. Full-matrix least-squares refinement gave a final R value of 0.068 for 2154 independent observed reflections. The two cyclopentadienyl rings are ~75-coordinated to the hafnium atom at an average Hf-C(r/5-) distance of 2.51(1) A. The Hf-Ncentroid (o-pyrrolyl) angles average 166 ~

Organometallics, 1985

The new compound Ga(C5Hd3 has been prepared and fully characterized by elementai analyses, cryoscopic molecular weight measurements, IR and 'H NMR data, Lewis acid-base studies, and an X-ray structural study. The new tricyclopentadienyl derivative is a colorless, volatile, pentane-soluble, crystalline solid, which decomposes very slowly at room temperature and more rapidly at 45 "C to form a yellow, pentane insoluble solid. An X-ray structural study of G B ( C~H~)~ demonstrates that the compound crystallizes in the monoclinic space group R 1 / n with unit cell dimensions a = 10.904 A, b = 8.928 (6) A, c = 13.533 (8) A, j3 = 92.19 (5)O, and d d d = 1.34 g for Z = 4. Full-matrix least-squares refinement led to a final R value of 0.057 for 371 observed reflections. The crystal consists of discrete isolated moelcules of Ga(C5H5I3, separated by normal van der Waals distances. There are no abnormally short intermolecular contacts.

Journal of Organometallic Chemistry, 1990

The verbenone-derived cyclopentadienyl compound ( 1S,8S)-7,7,9,9-tetramethyltricyclo[6.1.1.02~6]deca-2,fi-dienyllithium (VCpLi) yielded a 3:2 mixture of exo and endo deuterio quench products upon reaction with DzO at -78 "C in THF. Stereochemical identification was achieved by NMR analysis of Diels-Alder addition products. Reaction of VCpLi with Me3SiC1 under the same Conditions gave rise to a 9:l exo:endo product mixture. Silatropic shifts were observed in these quench products. According to NMR analysis, VCpLi consists nearly exclusively of the exo-Li monomer in THF at +26 "C. However, at -80 "C a ternary equilibrium of an exo-Li monomer, an exo,exo-Li sandwich dimer, and an endo,endo-Li sandwich dimer in a 5.1:2.8:1.0 molar ratio has been detected. Thermodynamic parameters for the monomer-dimer equilibrium are AH" = -3.6 f 0.2 kcal/mol and ASo = -15.6 f 0.9 eu. Due to ring current effects, unusual upfield 6Li chemical shifta are observed: 6 (ppm) = -7.83 (exo monomer), -12.22 (exo,exo dimer), and -12.25

J Chem Crystallography, 1982

The X-ray structure determination of (r;LCsHs)Ta(~LC2H4)C12(PMe2Ph)2 has revealed that the compound crystallizes in the orthorhombic space group Fdd2 with a = 21.098(9), b = 29.848(9), c = 7.694(3) A, and Dc = 1.70g cm -3 for Z = 8. Least-squares refinement based on 893 independent observed reflections resulted in a final R value of 0.026. The molecule resides on a crystallographic two-fold axis, with disordered ethylene and cyclopentadienyl groups. The Ta-C1 and Ta-P separations are 2.473(4) and 2.649(3) A, respectively. Since the two carbon atoms of the ethylene molecule are indistinguishable from two of the cyclopentadienyl carbon atoms, the Ta-C bond lengths are 2.37(1) and 2.39(2) A for the ethylene and for two of the cyclopentadienyl carbon atoms. The other three Ta-C(cyclopentadienyl) distances are much longer: 2.54(3), 2.54(3), and 2.62(3) A. In order to achieve 18 e-at the tantalum atom, the cyclopentadienyl ligand must be viewed in an r/Lbonding mode. The variation of the Ta-C lengths is thus considered to be steric in origen. The carbon atoms of the CsH~ group are planar to 0.03 A.