SYNTHESIS AND NMR-SPECTROSCOPY OF CYCLOPALLADATED TERTIARY PHOSPHITE COMPLEXES - X-RAY CRYSTAL-STRUCTURE OF PD(ETA-5-C5H5)(P(OPH)2(OC6H4))

A series of cyclopalladated tertiary phosphite complexes of structure [Pd(µ-Cl)(P(OR1)2(OC6H3R2))]2 (2), with R1 being either Ph or Et, has been prepared and studied with use of31P,13C, and1H NMR methods. For 2a (R1 = Ph, R2 = H) there are two isomers that have been assigned to the sym-cis and sym-trans structures and that are in equilibrium as shown by31P 2-D exchange NMR spectroscopy. For the platinum analogue of 2a, the exchange can be shown to be intramolecular, again via 2-D exchange NMR spectroscopy. An analysis of the13C NMR characteristics for 2 and some mononuclear derivatives obtained with use of PPh3, AsPh3, C≡NBut, diphos, CH3CN, and η5-C5H5 suggests that the low-field shift of the palladated carbon arises from the nature of the Pd ̶ C bond and not a ring effect. Various approaches to the syntheses of 2 are discussed, and cyclopalladation of P(OEt)2(NMePh) is presented. The molecular structure of Pd(η5-C5H5)(P(OPh)2(OC6H4)) has been determined by X-ray diffraction. The complex crystallized in the space group P212121, with a = 9.197 (4) Å, b = 10.807 (3) Å, c = 20.718 (3) Å, V = 2059 (2) Å3, and Z = 4. The structure was refined to R = 0.045. Relevant bond distances (Å) and angles (deg) are as follows: Pd‒P = 2.150 (2), Pd‒C(2) = 2.026 (6), Pd‒C(19) = 2.347 (9), Pd‒C(20) = 2.301 (7), Pd‒C(21) = 2.346 (7), Pd‒C(22) = 2.283 (7), Pd‒C(23) = 2.300 (7); P‒Pd‒C(2) = 80.2 (2). The dihedral angle between the P‒Pd‒C(2) and η5-C5H5 planes is 87.1°. © 1990, American Chemical Society. All rights reserved.