engleski

Structure and Relative Stability of Dirhodium Tetracamphanate Adducts with 5-Pyrido-1, 4-benzodiazepines and Their 4, 5-Dihydro Congeners-First Representatives of Non-Symmetric Bidentate 1, 4-Bisnitrogen Ligands

1H-NMR Spectra of dirhodium tetracamphanate adducts with 5-pyrido-1, 4-benzodiazepin-2-ones 3-5 reveal different modes of complexation. Depending on the structure of the chelating pyridobenzodiazepine, two types of kinetic and dynamic profiles are observed. Ligands 3 and 4, possessing a 1, 4-bisnitrogen subunit with 4p electrons, behave as bidentate ligands and form the kinetically stable 1:1 adducts, non-symmetric diastereomers 6A, 7A, which undergo fast isomerization into the thermodynamically more stable 6A, 7B. Ligand 5 (4, 5-dihydro derivatative of 4) behaves as a pyridine derivative, forming kinetically stable, symmetric 2:1 adduct 8, which very slowly isomerizes into non-symmetric 1:1 adduct 9. The relative stability of 8 is attributed to the hydrogen bonding N(4)-H-O(camphanyl), as well as to the low coordinating ability of the non-conjugated, pyramidal N(4) atom.

crystal-structure ; enantioselective cyclopropanation ; rhodium(ii) carboxylates ; chiroptical properties ; metal-complexes ; binding ; catalysis ; 2, 2'-bipyridine ; hydrogenation ; carboxamides

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