- SUBSTITUTED DERIVATIVES OF TRIS(BUTADIENE)-MOLYBDENUM AND -TUNGSTEN; THE MOLECULAR STRUCTURES OF (CH2=CMeCMe=CH2)3M (M = Mo, W)
-
Tris(substituted butadiene) complexes of molybdenum and tungsten have been prepared by the reduction of the metal halides with anthracene-activated magnesium in the presence of the appropriate diene.An X-ray diffraction study has shown tris(2,3-dimethylbutadiene)molybdenum and its tungsten analogue to be isomorphous, with each unit displaying a long-short-long bond alternation, and having short metal to terminal carbon atom distances, in marked contrast to the unsubstituted complexes.
- Bogdanovic, Borislav,Boennemann, Helmut,Goddard, Richard,Startsev, Anatolii,Wallis, Julian M.
-
-
Read Online
- UV PHOTOELECTRON SPECTRAL AND THEORETICAL STUDIES ON TRIS(BUTADIENE)-MOLYBDENUM AND -TUNGSTEN
-
The UV photoelectron spectra of tris(butadiene)molybdenum and -tungsten have been recorded and assigned with the assistance of extended Hueckel molecular orbital calculations.The spectra and calculations indicate substantial electron transfer from the metal to the ligand.The molecular orbital calculations have also indicated why these molecules adopt a trigonal prismatic rather than a octahedral geometry about the metal atom.The unusual C-C bond lengths in these complexes have been confirmed by a redetermination of the structure of tris(butadiene)molybdenum by X-ray crystallographic techniques and are discussed in the light of the calculations.
- Green, Jennifer C.,Kelly, M. Ruth,Grebenik, Peter D.,Briant, Clive E.,McEvoy, Neil A.,Mingos, D. Michael P.
-
-
Read Online
- Magnesium butadiene as a reagent for the preparation of transition-metal butadiene complexes: Molecular structure of bis(η-butadiene)[1,2-bis(dimethylphosphino)ethane]hafnium
-
The conveniently prepared reagent Mg(C4H6)·2THF reacts readily with transition-metal halides, forming butadiene complexes. Thus Hf(η-C4H6)2(dmpe), Ti(η-C4H6)2(depe), Ti(η-C4H6)2[(MeO)2PC 2H4P(OMe)2], Ti(η-C4H6)2(diphos), and Zr(η-C4H6)2(dmpe) are formed when MCl4 (M = Ti, Zr, Hf) and the appropriate bidentate phosphine (dmpe = 1,2-bis(dimethylphosphino)ethane, depe = 1,2-bis(diethylphosphino)ethane, diphos = 1,2-bis(diphenylphosphino)ethane) are treated with Mg(C4H6)·2THF. Similarly, NbCl4(dmpe)2, WCl6, and FeCl2 or FeCl3 adducts of trimethylphosphine react with the reagent, affording NbCl(C4H6)(dmpe)2, W(η-C4H6)3, and Fe(η-C4H6)(PMe3)3, respectively. Ti(C4H6)2(diphos) polymerizes ethylene. Hf(η-C4H6)2(dmpe) is triclinic, space group P1, with a = 13.274 (2) A?, b = 14.952 (2) A?, c = 9.319 (1) A?, α = 97.14 (1)°, β = 101.82 (1)°, γ = 109.76 (1)°, Z = 4, and ρ(calcd) = 1.742 g cm-3. The complex has no crystallographically imposed symmetry but has a structure based on a distorted C2 octahedral geometry. The Zr-C4H6 arrangement is η4 but distorted toward a 1,4-η2-C4H6 structure, reflecting substantial π interaction.
- Wreford,Whitney
-
p. 3918 - 3924
(2008/10/08)
-