2-DIMENSIONAL H-1 NOESY OF PD(II) PI-ALLYL COMPLEXES - THE CONCEPT OF REPORTER LIGANDS AND THE MOLECULAR-STRUCTURE OF [PD(ETA-3-CH2CCHCH2CH2CH2)(BIQUINOLINE)]CF3SO3

A series of [Pd(iD3-allyl)(nitrogen chelate)]CF3S03 complexes containing the coordinated /3-pinene allyl or the five-membered cyclic ΟΗ^ό-^ΟΗΟΙ^ΟΙ^όί^ allyl with biquinoline and phenanthroline (among others) as nitrogen chelate have been prepared and subjected to one- and two-dimensional Ή NMR studies. The 2-D nuclear Overhauser effect (NOE) results with phenanthroline and bipyridyl permit the determination of subtle aspects of their three-dimensional solution structure and specifically selective distortions in the hybridization of the allyl CH2 such that the syn proton moves slightly toward the metal and the anti proton significantly away from the palladium. Interligand NOEs may also be used to assign the coordinated face of the /3-pinene allyl ligand. Not all “reporter” ligands demonstrate NOE selectivity as shown by NMR as well as the molecular structure of the cyclic allyl [Pd(773-CH2CCHCH2CH2CH2)(biquinoline)](CF3S03), 3a, determined via X-ray diffraction methods. Complex 3a crystallizes in the space group P2Jn with α = 11.062 (1) Â, b = 14.595 (3) Â, c = 14.401 (1) Â, β = 94.33 (1)°, V = 2318.6 (8) A3, Ζ = 4. Relevant bond distances are as follows: Pd-N, 2.127 (2) and 2.121 (2) Â; Pd-C(ll), 2.129 (3) Â; Pd-C(12), 2.131 (2) Â; Pd-C(13), 2.168 (2) Â. The reporter protons, H(8) and H(8’), of the biquinoline are both ca. 2.5 Â from their respective ττ-allyl counterparts. This accounts for the substantial interligand NOEs but the lack of selectivity. © 1990, American Chemical Society. All rights reserved.