Gehinderte Ligandbewegungen in Übergangsmetallkomplexen, XLII [1]: Photoreaktionen von Hexacarbonyl-μ-η5:5-fulvalen-dimolybdän und -diwolfram mit konjugierten Dienen / Hindered Ligand Movements in Transition Metal Complexes, XLII [1]: Photoreactions of Hexacarbonyl-μ–η5:5-fulvalene-dimolybdenum and -ditungsten with Conjugated Dienes

Autor: Cornelius G. Kreiter, Wolfgang Conrad, Reiner Exner
Rok vydání: 1993
Předmět:
Zdroj: Zeitschrift für Naturforschung B. 48:1635-1650
ISSN: 1865-7117
0932-0776
DOI: 10.1515/znb-1993-1124
Popis: Photochemical reactions of hexacarbonyl-μ-η5:5-fulvalene-dimolybdenum (1) with 1,3-butadiene (a), 2-methyl-1,3-butadiene (b), E-1,3-pentadiene (c), 2,3-dimethyl-1,3-butadiene (d), and E-3-methyl-1,3-pentadiene (e) yield the corresponding tetracarbonyl-η4-s-cisdiene-μ-η5:5-fulvalene-dimolybdenum complexes 3a-3e. In addition to 3a also η4-s-trans1,3-butadiene-tetracarbonyl-μ-η5:5-fulvalene-dimolybdenum (4) is formed. Similarily hexacarbonyl-μ-η5:5-fulvalene-ditungsten (2) forms with a and b tetracarbonyl-η4-s-cis-diene-μ-η5:5-fulvalene-ditungsten (5a, 5b) and bis(η4-s-cis-1,3-butadiene)-dicarbonyl-μ-η5:5-fulvalene-ditungsten (6). The complexes 3b —3e and also 5b are obtained as mixtures of the o- and u-isomers. Only for tetracarbonyl-η4-cis-2,3-dimethyl-1,3-butadiene-μ-η5:5-fulvalene-dimolybdenum (3d) an interconversion of the o- and u-isomers is observed with an energy barrier of ΔG183 # = 73.9 kJ/mol. Both isomers of 3d show hindered inversions with energy barriers of ΔG# 313 = 66.1 kJ/mol (u-3d) and ΔG183 # = 36.4 kJ/mol (o-3d). For o-3d the crystal and molecular structure was determined by an X-ray diffraction analysis. Hexacarbonylµ — η5:5-bis(cyclopentadiendiyl)methane-dimolybdenum (7), hexacarbonyl-μ-η5:5-bis(cyclopentadiendiyl)ethane-dimolybdenum and hexacarbonyl-μ-η5:5-bis(cyclopentadiendiyl)propane-dimolybdenum do not react with conjugated dienes. Upon UV irradiation 7 looses CO and forms by dimerization octacarbonyl-bis(μ-η5:5-(cyclopentadiendiyl-cyclopentadien-triyl)methane)-dihydrido-tetramolybdenum (8).
Databáze: OpenAIRE
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