Cycloaddition reactions with α,β-unsaturated carbene complexes of the Fischer-type bearing the carbene carbon atom and the double bond incorporated in the same ring are described. Pentacarbonyl(2H-benzopyran-2- ylidene)chromium(0) complexes (2a-c) and pentacarbonyl(4-methoxy-3,3-dimethyl-2-oxacyclopentylidene)- chromium(0) (3) show a rather low reactivity towards 1,3-dipoles and 1,3-dienes. The reactions with diazomethane are regioselective but not chemoselective; compounds 2 and 3 show two sites of attack: the α,β carbon-carbon and the carbon-metal double bond. The crystal and molecular structures of 2a and 3 have been elucidated by single crystal X-ray analysis. Crystals of 2a are monoclinic, space group P21/c, a=7.614(3), b=14.033(3), c=12.766(3) Å, β=95.24°, V=1358.3(7) Å Z=4; crystals of 3 are triclinic, space group P1, a=6.553(1), b=9.408(1), c=10.620(1) Å α=92.70(1), β=92.30(1), γ=92.12(1)°, V=653.0(1), Å3, Z=2. Final agreement indices for 2a and 3 are R=0.034 and 0.033, respectively. Vibrational properties of the Cr(CO)5 moiety were interpreted by FT-IR and FT-Raman spectroscopy. Electronic spectra and π electron distribution were interpreted by resonance Raman spectroscopy.
A STUDY OF THE REACTIVITY AND STRUCTURE OF CYCLIC ALPHA,BETA-UNSATURATED FISCHER-TYPE CARBENE COMPLEXES / E. LICANDRO, S. MAIORANA, A. PAPAGNI, A. GEROSA, F. CARIATI, S. BRUNI, M. MORET, A. VILLA. - In: INORGANICA CHIMICA ACTA. - ISSN 0020-1693. - 220:1-2(1994), pp. 233-247. [10.1016/0020-1693(94)03875-9]
A STUDY OF THE REACTIVITY AND STRUCTURE OF CYCLIC ALPHA,BETA-UNSATURATED FISCHER-TYPE CARBENE COMPLEXES
E. LicandroPrimo
;S. MaioranaSecondo
;F. Cariati;S. Bruni;
1994
Abstract
Cycloaddition reactions with α,β-unsaturated carbene complexes of the Fischer-type bearing the carbene carbon atom and the double bond incorporated in the same ring are described. Pentacarbonyl(2H-benzopyran-2- ylidene)chromium(0) complexes (2a-c) and pentacarbonyl(4-methoxy-3,3-dimethyl-2-oxacyclopentylidene)- chromium(0) (3) show a rather low reactivity towards 1,3-dipoles and 1,3-dienes. The reactions with diazomethane are regioselective but not chemoselective; compounds 2 and 3 show two sites of attack: the α,β carbon-carbon and the carbon-metal double bond. The crystal and molecular structures of 2a and 3 have been elucidated by single crystal X-ray analysis. Crystals of 2a are monoclinic, space group P21/c, a=7.614(3), b=14.033(3), c=12.766(3) Å, β=95.24°, V=1358.3(7) Å Z=4; crystals of 3 are triclinic, space group P1, a=6.553(1), b=9.408(1), c=10.620(1) Å α=92.70(1), β=92.30(1), γ=92.12(1)°, V=653.0(1), Å3, Z=2. Final agreement indices for 2a and 3 are R=0.034 and 0.033, respectively. Vibrational properties of the Cr(CO)5 moiety were interpreted by FT-IR and FT-Raman spectroscopy. Electronic spectra and π electron distribution were interpreted by resonance Raman spectroscopy.Pubblicazioni consigliate
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