Synthesis, Structural Characterization, and Properties of Some Functionalized Phosphine-Containing Diiron Complexes As Models for the Active Site of [FeFe]-Hydrogenases

The first phosphinobenzaldehyde- and phosphinoporphyrin-functionalized
model complexes (1–4) have been synthesized
and structurally characterized. Thus, reaction of diiron complex [(μ-SCH2)2CH2]­Fe2(CO)6 or [(μ-SCH2)2NC6H4CO2Me-p]­Fe2(CO)6 with p-Ph2PC6H4CHO in the presence of Me3NO gave the phosphinobenzaldehyde-functionalized
model complexes [(μ-SCH2)2CH2]­Fe2(CO)5(p-Ph2PC6H4CHO) (1) and [(μ-SCH2)2NC6H4CO2Me-p]­Fe2(CO)5(p-Ph2PC6H4CHO) (2) in 61% and
71% yields, respectively. Further reaction of 1 or 2 with PhCHO, pyrrole, and BF3·OEt2 followed by treatment with p-chloranil resulted
in formation of the phosphinoporphyrin-functionalized model complexes
5-{[(μ-SCH2)2CH2]­Fe2(CO)5(p-Ph2PC6H4)}-10,15,20-triphenylporphyrin (3) and 5-{[(μ-SCH2)2NC6H4CO2Me-p]­Fe2(CO)5(p-Ph2PC6H4)}-10,15,20-triphenylporphyrin
(4) in 19% and 18% yields, respectively. While the new
complexes 1–4 were characterized
by elemental analysis and spectroscopy, the structures of 1, 3, and 4 were confirmed by X-ray crystallography.
Particularly interesting is that complex 4 was found
to be a catalyst for the photoinduced H2 production in
the presence of the electron donor EtSH and the proton source HOAc.