Inorganic Chemistry
COMMUNICATION
To determine whether μ-N2H2 4 further reacts with hy-
drazine to generate N2 and NH3, 0.95 equiv of 15N2H4 was
added to a THF solution of 4, and both the reaction volatiles
and residual solids were analyzed by NMR spectroscopy. 1H
NMR analysis of the volatiles established the formation of
15NH3 (ca. 50% yield) and no 14NH3. 1H and 31P NMR spec-
troscopy of the residual solids indicated that acetate 1and ammonia 5
were the major iron-containing products, with 14N 4 present as a
minor species. These results are consistent with a disproportionation
mechanism in which the bound diazene is oxidized to N2 by free
N2H4, which itself is reduced to NH3.
’ ACKNOWLEDGMENT
We acknowledge the NIH (Grant GM-070757). Funding
for the Caltech NMR facility has been provided, in part, by the
NIH (Grant RR027690). C.T.S. is grateful for an NSF graduate
fellowship.
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Although 1 can serve as a hydrazine disproportionation catalyst
(in the presence of 10 equiv of N2H4, a 16% yield of NH3 is
obtained), the reaction is hampered by ligand degradation; in
addition to 1 and 5, (CH2Cy)2PMe and other, unidentifiable
products are present in the resulting 1H and 31P NMR spectra.
The ability to isolate iron complexes that only differ in the
extent of reduction of the nitrogenous ligand suggests the
possibility that these complexes may be interconverted via
redox reactions. Although the cyclic voltammogram of μ-N2 2
(obtained at ꢀ35 °C) shows a quasi-reversible reduction at ca.
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In summary, a series of mono- and diiron(II) complexes that
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available sixth coordination site have been prepared and
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nated NxHy ligand and, hence, present an attractive synthetic
system for studying aspects of an alternating N2 reduction
scheme. The finding that μ-N2H4 3 and μ-N2H2 4 react with
free hydrazine, reducing the latter to NH3 as the former is
oxidized, suggests that a similar reactivity pattern merits con-
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’ ASSOCIATED CONTENT
S
Supporting Information. Crystallographic details for 2,
b
4, and 5 in CIF format, detailed experimental procedures, and
characterization data for 1ꢀ5. This material is available free of
’ AUTHOR INFORMATION
Corresponding Author
*E-mail: jpeters@caltech.edu.
11287
dx.doi.org/10.1021/ic2016066 |Inorg. Chem. 2011, 50, 11285–11287