Variants of Solid‐State and Solution Structures of (η 3 ‐Allyl)‐ {2‐[2′‐(diphenylphosphino)phenyl]‐4,5‐dihydrooxazole‐ P , N }palladium(II) hexafluorophosphates and tetraphenylborates

Crystal and solution structures of the enantiomerically pure and the racemic pairs of (η 3 ‐allyl) {2‐[2′‐(diphenylphosphino)phenyl]‐4,5‐dihydro‐4‐phenyloxazole}palladium(II) hexafluorophosphates ( 1 , and rac ‐ 1 , resp.) and tetraphenylborates ( 2 , and rac ‐ 2 , resp.) as well as (η 3 ‐allyl){2‐[2′‐(diphenylphosphino)phenyl]‐4,5‐dihydro‐4‐isopropyloxazole}palladium(II) tetraphenylborate ( 3 ) were characterized by X‐ray crystallography and 1 H‐NMR spectroscopy. In the solid state, rac ‐ 1 and rac ‐ 2 proved to be disordered with both diastereoisomeric complexes in the crystal. The complexes 2 and 3 exist only in the ‘ exo ’ form. The X‐ray structures show that the [Pd II (η 3 ‐allyl)] moiety may adopt different configurations between a nearly symmetrical three‐electron Pd II (π 3 ‐allyl) system and an asymmetrical allyl group with a η 1 ‐ and a η 2 ‐bonding to the metal center. The [Pd II (η 3 ‐allyl)] system of rac ‐ 1 and of ‘ endo ’ rac ‐ 2 is closer to the former, and that of 2 , ‘ exo ’‐ rac ‐ 2 , and 3 closer to the later geometry. The 1 H‐NMR spectra of the hexafluorophosphates 1 and rac ‐ 1 show two sets of signals of the allylic protons in an ‘ exo ’/‘ endo ’ ratio of 2:3. The tetraphenylborates 2 , rac ‐ 2 , and 3 give only one set of broad signals of the allylic protons.