Hydride Transfer from Iron(II) Hydride Compounds to NAD(P)+ Analogues

Iron(II) hydride complexes of the “piano-stool” type, Cp*(P-P)FeH (P-P = dppe (1H), dppbz (2H), dppm (3H), dcpe (4H)) were examined as hydride donors in the reduction of N-benzylpyridinium and acridinium salts. Two pathways of hydride transfer, “single-step H–” transfer to pyridinium and a “two-step (e–/H•)” transfer for acridinium reduction, were observed. When 1-benzylnicotinamide cation (BNA+) was used as an H– acceptor, kinetic studies suggested that BNA+ was reduced at the C6 position, affording 1,6-BNAH, which can be converted to the more thermally stable 1,4-product. The rate constant k of H– transfer was very sensitive to the bite angle of P–Fe–P in Cp*(P-P)FeH and ranged from 3.23 × 10–3 M–1 s–1 for dppe to 1.74 × 10–1 M–1 s–1 for dppm. The results obtained from reduction of a range of N-benzylpyridinium derivatives suggest that H– transfer is more likely to be charge controlled. In the reduction of 10-methylacridinium ion (Acr+), the reaction was initiated by an e– transfer (ET) process and then...