STRUCTURE AND RELATIVE STABILITY OF DIRHODIUM TETRACAMPHANATE ADDUCTSWITH 5-PYRIDO-1,4-BENZODIAZEPINES AND THEIR 4,5-DIHYDRO CONGENERS FIRST REPRESENTATIVES OF NONSYMMETRICAL BIDENTATE 1,4-BISNITROGEN LIGANDS

H-1-NMR Spectra of dirhodium tetracamphanate adducts with 5-pyrido-1,4 -benzodiazepin-2-ones 3-5 reveal different modes of complexation. Depe nding on the structure of the chelating pyridobenzodiazepine, two type s of kinetic and dynamic profiles are observed. Ligands 3 and 4, posse ssing a 1,4-bisnitrogen subunit with 4 pi electrons, behave as bidenta te ligands and form the kinetically stable 1:1 adducts, non-symmetric diastereomers 6A, 7A, which undergo fast isomerization into the thermo dynamically more stable 6B, 7B. Ligand 5 (4,5-dihydro derivative of 4) behaves as a pyridine derivative, forming the kinetically stable, sym metric 2:1 aduct 8, which very slowly isomerizes into non-symetric 1:1 aduct 9. The relative stability of 8 is attributed to the hydrogen bo nding N(4)-H-O(camphanyl), as well as to the low coordinating ability of the non-conjugated, pyramidal N(4) atom.