Rhenium Complexes Containing the Chiral Tridentate Ferrocenyl Ligand Pigiphos

The paramagnetic Re(III) complex [ReCl3(Pigiphos)] (1) ((R)-(S)-Pigiphos = bis{(R)-1-[(S)-2-(diphenylphosphino)ferrocenyl]ethyl}cyclohexylphosphine) is accessible from [ReCl3(NCMe)(PPh3)2] and the ligand Pigiphos. 1 reacts with an excess of NaBH4, affording the polyhydride complex [ReH5(Pigiphos)] (2), which was shown to be a classic polyhydride (NMR T1(min) = 158 ms). This complex reacts readily with both Brønsted acids and hydride scavengers to give the corresponding cationic tetrahydride species, which was shown to be active in the catalytic hydrogenation of dimethyl itaconate.