Crystallographic and NMR studies on chiral palladium(II) allyl ferrocene-based P,N complexes

Detailed crystallographic and NMR measurements are reported for several Pd(II) allyl complexes containing chiral ferrocene-based phosphinopyrazole ligands, CpFe{eta(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 influence for the PPh(2) donor moiety, based on C-13 data. The solid-state structure for 2 shows normal bond lengths, although there are indications that the allyl adjusts its position due to the relatively large P,N ligand. The solid- and solution-state structures of [Pd(eta(3)-PhCHCHCHPh)(1g)]PF6, 3g, R(1) = adamantyl and R(2) = H (99% ee in the enantioselective allylic amination), show the allyl ligand to be strongly rotated, thus placing the terminal allyl carbon proximate to the pyrazole moiety, significantly below the coordination plane. These structural results suggest that, for the enantioselective catalysis using ligands 1, there is an ''early'' transition state.