Hindered Ligand Movements in Transitionmetal Complexes, XXI [1] Isomerism and Dynamics of cis-Dicarbonyl-bis(η4-2-methyl-l,3-butadiene)tungsten(0) Gehinderte Ligandbewegungen in Übergangsmetall-Komplexen, XXI [1] Isomerie und Dynamik von cis-Dicarbonyl-bis(η4-2-methyl-1.3-butadien)wolfram(0)

Kreiter, Cornelius G.
Özkar, Saim
cis-Dicarbonyl-bis(2-methyl-l,3-butadiene)molybdenum(0) (1) and -tungsten(O) (2) were prepared photochemically from tricarbonylmesitylene-molybdenum(O) and aceto-nitrile-pentacarbonyl-tungsten(O), respectively, as thermolabile yellow oils. 2 is obtained as a mixture of two diastereomeric pairs of enantiomers 2a (2a') and 2c (2c'). From XH and 13C NMR spectroscopic data 2 a (2a') is shown to have C2 symmetry, whereas 2 c (2c') is asymmetric. The NMR signals of 2 c (2 c') are temperature dependent due to an intramolecular 2c^±2c'-isomerization (A G+25o = 47 kJ • mol-1). A trigonal prismatic transi-tion state with Cs symmetry explains the D-NMR spectroscopic results. The NMR signals of 2 a (2a') are temperature dependent, too. This is taken as evidence for a ligand move-ment which brings 2a (2a') on the way to a third diastereomeric form 2b' (2b), with no detectable population. The molybdenum complex 1 forms only the isomers la (la') with C2 symmetry.
Zeitschrift fur Naturforschung - Section B Journal of Chemical Sciences


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Citation Formats
C. G. Kreiter and S. Özkar, “Hindered Ligand Movements in Transitionmetal Complexes, XXI Isomerism and Dynamics of cis-Dicarbonyl-bis(η4-2-methyl-l,3-butadiene)tungsten(0) Gehinderte Ligandbewegungen in Übergangsmetall-Komplexen, XXI Isomerie und Dynamik von cis-Dicarbonyl-bis(η4-2-methyl-1.3-butadien)wolfram(0),” Zeitschrift fur Naturforschung - Section B Journal of Chemical Sciences, vol. 38, no. 11, pp. 1424–1430, 1983, Accessed: 00, 2023. [Online]. Available: https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84921232118&origin=inward.