CRYSTALLOGRAPHIC AND NMR-STUDIES ON CHIRAL PALLADIUM(II) ALLYL FERROCENE-BASED P,N COMPLEXES

Detailed crystallographic and NMR measurements are reported for severa l Pd(II) allyl complexes containing chiral ferrocene-based phosphinopy razole ligands, a(5)-C5H3(1-CH(CH3)(NN=C(R(1)CH=CR(2))-2-PPh(2))}, 1. Relative to similar BINAP, CHIRAPHOS, and diphosphine JOSIPHOS analogs , the major isomer of the beta-pinene allyl complex [Pd(eta(3)-C10H15) (1a)]CF3SO3, 2, R(1) = R(2) = H, shows a surprisingly large trans infl uence for the PPh(2) donor moiety, based on C-13 data. The solid-state structure for 2 shows normal bond lengths, although there are indicat ions that the allyl adjusts its position due to the relatively large P ,N ligand. The solid- and solution-state structures of [Pd(eta(3)-PhCH CHCHPh)(1g)]PF6, 3g, R(1) = adamantyl and R(2) = H (99% ee in the enan tioselective allylic amination), show the allyl ligand to be strongly rotated, thus placing the terminal allyl carbon proximate to the pyraz ole moiety, significantly below the coordination plane. These structur al results suggest that, for the enantioselective catalysis using liga nds 1, there is an ''early'' transition state.