Journal article
Desymmetrized Diiron Azadithiolato Carbonyls: A Step Toward Modeling the Iron-Only Hydrogenases
Organometallics, Vol.27(1), pp.119-125
01/2008
Handle:
https://hdl.handle.net/2376/109037
PMCID: PMC2427274
PMID: 18552987
Abstract
Condensation of Fe
2
(SH)
2
(CO)
6
, acetaldehyde, and (NH
4
)
2
CO
3
affords the methyl-substituted azadithiolate Fe
2
[(SCHMe)
2
NH](CO)
6
(
1
). The complex exists mainly (~95%) as the meso diastereomer, but the
d,l
diastereoisomers could be detected. DFT calculations predict that the meso isomer would be 2.5 kcal/mol more stable than the
d,l
isomer due to conventional nonbonding interactions between the methyl groups and the ring hydrogen atoms. Crystallographic analysis of
meso
-
1
confirms that the two methyl groups are equatorial, constraining the diferraazadithiolate bicycle to a conformation that desymmetrizes the diiron center. The lowered symmetry is confirmed by the observation of two
13
C NMR signals in the Fe
C
O region under conditions of fast turnstile rotation at the Fe(CO)
3
groups. The p
K
a
value of the amine in
1
is 7.89 (all p
K
a
’s determined in MeCN solution), which is similar to a redetermined value for Fe
2
[(SCH
2
)
2
NH](CO)
6
(
2
, p
K
a
= 7.98) and only slightly less basic than the tertiary amine Fe
2
[(SCH
2
)
2
NMe](CO)
6
(p
K
a
= 8.14). Substitution of
1
with PMe
3
proceeded via the intermediacy of two isomers of Fe
2
[(SCHMe)
2
NH](CO)
5
(PMe
3
), affording Fe
2
[(SCHMe)
2
NH](CO)
4
(PMe
3
)
2
(
3
).
31
P NMR spectra confirm that the two PMe
3
ligands in
3
are nonequivalent, consistent with the desymmetrizing effect of the dithiolate. The p
K
a
value of the amine in
3
was found to be 11.3. Using triphenylphosphine, we prepared Fe
2
[(SCHMe)
2
NH](CO)
5
(PPh
3
) as a single regioisomer.
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Details
- Title
- Desymmetrized Diiron Azadithiolato Carbonyls: A Step Toward Modeling the Iron-Only Hydrogenases
- Creators
- Jane L Stanley - Department of Chemistry, University of Illinois at Urbanas—Champaign, Urbana, Illinois 61801Zachariah M Heiden - Department of Chemistry, University of Illinois at Urbanas—Champaign, Urbana, Illinois 61801Thomas B Rauchfuss - Department of Chemistry, University of Illinois at Urbanas—Champaign, Urbana, Illinois 61801Scott R Wilson - Department of Chemistry, University of Illinois at Urbanas—Champaign, Urbana, Illinois 61801Luca De Gioia - Department of Biotechnology and Biosciences, University of Milano-Bicocca, Piazza della Scienza 1, 20126-Milan, ItalyGuiseppe Zampella - Department of Biotechnology and Biosciences, University of Milano-Bicocca, Piazza della Scienza 1, 20126-Milan, Italy
- Publication Details
- Organometallics, Vol.27(1), pp.119-125
- Academic Unit
- Chemistry, Department of
- Identifiers
- 99900546759001842
- Language
- English
- Resource Type
- Journal article