15N NMR studies on cyclopalladated Schiff's base complexes

0749-1581

Chemistry ; Analytical Chemistry and Spectroscopy

Wiley InterScience Backfile Collection 1832-2000

Chemistry and Pharmacology

15N NMR spectra for a series of cyclopalladated m- and p-substituted benzylidene Schiff's base complexes have been measured. The dominant factor affecting the nitrogen chemical shift is the ligand in the trans position to the coordinated nitrogen, and not the aryl ring substituent. Tertiary phosphine ligands trans to the 15N=CH moiety weaken the Pd-N bond more than oxygen, chlorine or nitrogen donors, thereby reducing the coordination chemical shift. The values for δ(15N) in the free and complexed ligands correlate linearly with one another.1H and 15N spectra of the geometric isomers [Pd(2a)Cl(pyridine)] and [Pd(2a)Cl(NHEt2)], where 2a = the 2′-cyclopalladated Schiff's base (5′-OCH3C6H3)CH=N(4-CH3C6H4), were assigned based on the local anisotropic effects of the Cl and nitrogen ligand. For the pyridine complex the assignment is supported by difference NOE, NOESY and COSY measurements.

2 Ill.

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