Iron(II) Complexes of the Linear <i>rac-</i>Tetraphos‑1 Ligand as Efficient Homogeneous Catalysts for
Sodium Bicarbonate Hydrogenation and Formic Acid Dehydrogenation
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Abstract
The
linear tetraphosphine 1,1,4,7,10,10-hexaphenyl-1,4,7,10-tetraphosphadecane
(tetraphos-1, P4) was used as its <i>rac</i> and <i>meso</i> isomers for the synthesis of both molecularly defined
and in situ formed Fe(II) complexes. These were used as precatalysts
for sodium bicarbonate hydrogenation to formate and formic acid dehydrogenation
to hydrogen and carbon dioxide with moderate to good activities in
comparison to those for literature systems based on Fe. Mechanistic
details of the reaction pathways were obtained by NMR and HPNMR experiments,
highlighting the role of the Fe(II) monohydrido complex [FeH(<i>rac</i>-P4)]<sup>+</sup> as a key intermediate. X-ray crystal
structures of different complexes bearing <i>rac</i>-P4
were also obtained and are described herein