posted on 2014-02-03, 00:00authored byDehua Zheng, Mei Wang, Lin Chen, Ning Wang, Licheng Sun
A diiron dithiolate complex with
a pendant phosphine coordinated
to one of the iron centers, [(μ-SCH2)2N(CH2C6H4-o-PPh2){Fe2(CO)5}] (1),
was prepared and structurally characterized. The pendant phosphine
is dissociated together with a CO ligand in the presence of excess
PMe3, to afford [(μ-SCH2)2N(CH2C6H4-o-PPh2){Fe(CO)2(PMe3)}2] (2). Redox reactions of 2 and related complexes
were studied in detail by in situ IR spectroscopy. A series of new
FeIIFeI ([3]+ and [6]+), FeIIFeII ([4]2+), and FeIFeI (5) complexes relevant to Hox, HoxCO, and Hred states of the [FeFe]-hydrogenase active site
were detected. Among these complexes, the molecular structures of
the diferrous complex [4]2+ with the internal
amine and the pendant phosphine co-coordinated to the same iron center
and the triphosphine diiron complex 5 were determined
by X-ray crystallography. To make a comparison, the redox reactions
of an analogous complex, [(μ-SCH2)2N(CH2C6H5){Fe(CO)2(PMe3)}2] (7), were also investigated by
in situ IR spectroscopy in the absence or presence of extrinsic PPh3, which has no influence on the oxidation reaction of 7. The pendant phosphine in the second coordination sphere
makes the redox reaction of 2 different from that of
its analogue 7.