Synthesis and Characterization of Dihydrogen and Dihydride Complexes of [CpMH₂(diphosphine)]⁺ (M = Fe, Os)

Abstract

Protonation of CpFeH(P-P) (P-P = dppe, dppp) with HBF4 produced the molecular dihydrogen complexes [CpFe(H2)(P-P)]BF4. Protonation of CpOsH(P-P) (P-P = dppm, dppe, dppp) with HBF4 at −78 °C gave a mixture of cis-[CpOsH2(P-P)]BF4 and trans-[CpOsH2(P-P)]BF4. Depending on the size of the chelating rings, the thermodynamically stable structures of the protonated products at room temperature may be exclusively trans-[CpOsH2(P-P)]BF4 or a mixture of cis-[CpOsH2(P-P)]BF4 and trans-[CpOsH2(P-P)]BF4. At room temperature in dichloromethane solutions, [CpOsH2(dppm)]BF4 exists as a mixture of cis and trans isomers in a ratio of 10:1, [CpOsH2(dppe)]BF4 exists as a mixture of cis and trans isomers in a ratio of 1:70, and [CpOsH2(dppp)]BF4 adopts only trans geometry.