Trans-Chelating Chiral Peralkyldiphosphine Ligands (R,R) -(S,S)-2,2″-Bis[1-(dialkylphosphino)ethyl]-1,1″-biferrocenes (AlkyITRAPs) and Their Transition Metal Complexes

New chiral peralkyldiphosphines (S,S)-2,2″-bis[(R)-1-(dialkylphosphino)ethyl]-1,1″-biferrocenes ((R,R)-(S,S)-al-kylTRAPs) were synthesized from (R)-N,N-dimethyl-1-ferrocenylethylamine in four steps in 38-68% overall yields (MeTRAP: 38%, EtTRAP: 68%, PrTRAP: 53%, BuTRAP: 56%, i-BuTRAP: 51%, i-PrTRAP: 42%). The reactions of alkylTRAP (Et-, Bu-, i-Bu, and i-PrTRAP) with 1 molar amount Of PdBr₂ gave tran-[PdBr₂(alkylTRAP)] in good yields. The X-ray crystal structures of these palladium complexes revealed that alkylTRAPs coordinated to a palladium atom in a trans-chelating manner regardless of the P-alkyl substituents. The structures of palladium complexes of Et-, Bu-, and i-PrTRAP had nearly C₂-symmetry, but that of i-BuTRAP was deviated from C2-symmetry significantly. AlkylTRAPs also reacted with [PtCl₂(MeCN₂] and [RhCl(CO₂]₂, giving the corresponding trans-chelate platinum and rhodium complexes. The crystal structure of tran [RhCl(CO)(BuTRAP)] revealed that the conformation of the BuTRAP ligand in the complex was almost the same as that in the palladium complex trans-[PdBr₂(BuTRAP)].