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RESEARCH PRODUCT

ChemInform Abstract: Theoretical and Spectroscopic Studies on Imino-Carbon Palladated Pyridine-2-carbaldimines.

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Abstract Ab initio LCAO-MO-SCF calculations on the model compounds C 5 H 4 N-2-C(R 1 )=NH [R 1 = H ( 2c ) and R 1 = trans -PdCl(PH 3 ) 2 ( 4c )] indicate that the E - trans conformation is favored over the E - cis one by 16.9 kJ mol −1 for 2c and by 25.0 kJ mol −1 for 4c . One of the factors which stabilizes the E-trans arrangement for 4c is a weak bonding interaction between the palladium center and the pyridine nitrogen. On going from 2c to 4c a slight charge enrichment on the pyridine carbons and a more pronounced one on the nitrogen atoms is computed, whereas the charge density of the imino carbon atom is decreased. In 4c no π contribution to the PdC bond is observed. Protonation of the organic moiety of 4c in the E-cis configuration gives rise to a weak PdC π overlap population and to a decreased energy separation between π* 5 ( LUMO ) and the highest energy occupied π MO (π 4 ) of the pyridine-2-carbald-imino moiety. The theoretical results are qualitatively related to structural and spectroscopic data (electronic, IR and 13 C NMR ) of pyridine-2-carbaldimines and the corresponding imino-carbon palladated derivatives.