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Organometallic paramagnetic camphor complexes. EPR investigation of their formation and structures
Author(s) -
Rebmann Andreas,
Mäurer Manfred,
Scheffler Klaus,
Stegmann Hartmut B.
Publication year - 1992
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1260300914
Subject(s) - chemistry , electron paramagnetic resonance , radical , diastereomer , paramagnetism , moiety , tin , photochemistry , ligand (biochemistry) , crystallography , stereochemistry , nuclear magnetic resonance , organic chemistry , biochemistry , physics , receptor , quantum mechanics
Photochemical reactions of camphor and other diones with carbonylmanganese or aryltin compounds lead to paramagnetic complexes. The radicals derived from Mn 2 (CO) 10 and Mn 2 (CO) 8 (PR 3 ) 2 are formulated as sixcoordinate complexes with different structures depending on the organic moiety, and they are characterized by their EPR and ENDOR data. Under the same conditions, the tin compounds form five‐coordinate complexes in which the organic ligand occupies one equatorial and one axial position in the bipyramidal structure. Consequently, two permutation isomers are expected if camphor quinone is used as a scavenger for the photolytically generated tin radicals, independent of the structure of the trapped species. These two species can be detected by ENDOR and triple resonance experiments if the interconversion is slow with respect to the EPR time scale. Diastereomeric complexes are obtained by the formation of a second chiral centre, at the tin atom, in the course of the reaction. However, these isomers cannot be distinguished by ENDOR spectroscopy under the conditions applied.