Showing papers by "Thomas F. Koetzle published in 1998"

Neutron Diffraction Study of [Nd(AlMe4)3]⋅0.5 Al2Me6 at 100 K: The First Detailed Look at a Bridging Methyl Group with a Trigonal‐Bipyramidal Carbon Atom

Abstract: Weak agostic Nd⋅⋅⋅H interactions and Nd-C bonds are involved in the bonding of the bridging methyl groups in the title compound (see sketch on the right): Two of the three H atoms of the methyl group are directed at the Nd center. The C atoms have distorted trigonal-bipyramidal geometry with the Nd atom and one of the H atoms (HA ) as axial ligands, and the Al atom and the other two H atoms (HB and HC ) in equatorial positions. The Al2 Me6 "solvate" molecule is disordered.

False Minima in X-ray Structure Solutions Associated with a “Partial Polar Ambiguity”: Single Crystal X-ray and Neutron Diffraction Studies on the Eight-Coordinate Tungsten Hydride Complexes, W(PMe3)4H2X2 (X = F, Cl, Br, I) and W(PMe3)4H2F(FHF)

Abstract: The molecular structures of the eight-coordinate tungsten hydride complexes W(PMe3)4H2X2 (X = F, Cl, Br, I) and W(PMe3)4H2F(FHF) have been determined by single-crystal X-ray diffraction; W(PMe3)4H2Cl2 and W(PMe3)4H2F(FHF) have also been analyzed by single-crystal neutron diffraction, thereby accurately locating the positions of the hydride ligands. The structures of all of these complexes are similar and are based on a trigonal dodecahedron, with a distorted tetrahedral array of PMe3 ligands in which two of the PMe3 ligands are displaced over the halide substituents. However, the initial structures derived for both W(PMe3)4H2Cl2 and W(PMe3)4H2F(FHF) did not exhibit the aforementioned geometry, but were based on an arrangement in which the two transoid-PMe3 ligands are displaced toward the two cis-PMe3 groups, rather than tilted toward the chloride ligands. Interestingly, the unexpected structures for W(PMe3)4H2Cl2 and W(PMe3)4H2F(FHF) were discovered to be the result of an artifact due to the presence of ...