Synthesis, Characterization and Catalytic Activity Studies of Rhenium Carbonyl Complexes Containing Chiral Diphosphines of the Josiphos and Walphos Families

Ten rhenium carbonyl complexes—[Re(H)(CO)3(1a)], [Re3(mu-H)3(CO)10(1a)], [Re2(CO)9(2a)], [Re2(CO)8(2a)], [Re2(CO)9(2b)], [{Re2(CO)9}2(2b)][Re2(CO)8(2b)], [Re2(CO)8(1b)], [Re2(mu-H)2(CO)6(2b)] and [Re3(mu-H)3(CO)11(2b)] containing different bidentate chiral phosphine ligands of theJosiphos (1a,1b) and Walphos(2a,2b) families have been synthesized and fully characterized (1a:(R)-1-{(SP)-2-[Bis[3,5-bis(trifluoromethylphenylphosphino]ferrocenyl} ethyldi(3,5-xylyl)phosphine,1b:(R)-1-{(SP)-2-[Di(2-furyl)phosphino]ferrocenyl}ethyldi-tert-butylphosphine,2a:(R)-1{(RP)-2-[2-[Bis(4-methoxy-3,5-dimethylphenyl)phosphino]phenyl]ferrocenyl}ethylbis[3,5-bis(trifluoromethyl)phenyl]phosphine and2b:(R)-1-{(RP)-2-[2- (Diphenylphosphino)phenyl]ferrocenyl}ethyldicyclohexylphosphine). The phos-phine-substituted clusters were tested for hydrogenation of tiglic acid [ trans-2-methyl-2-butenoic acid]. The catalytic reactions gave reasonable conversion rates(15–88 %) under relatively mild conditions but relatively moderate enantiomeric excesses (8–57 %) were observed. The crystal structures of [ReH(CO)3(1a)], [Re2(CO)9(2a)], [{Re2(CO)9}2(2b)] and [Re2(mu-H)(CO)6(2b)] are presented.