Issue 5, 2015

Synthesis and characterization of μ-nitrido, μ-carbido and μ-oxo dimers of iron octapropylporphyrazine

Abstract

Three μ-X bridged diiron octapropylporphyrazine complexes having FeIII–O–FeIII, Fe+3.5–N[double bond, length as m-dash]Fe+3.5 and FeIV[double bond, length as m-dash]C[double bond, length as m-dash]FeIV structural units have been prepared and characterized by UV-vis, EPR, X-ray absorption spectroscopy and electrochemical methods. Single crystals of all the complexes were obtained from benzene-acetonitrile and their structures were determined by X-ray diffraction. In contrast to μ-oxo complex (6), μ-nitrido (7) and μ-carbido (8) dimers crystallized with one benzene molecule per two binuclear complex molecules arranged cofacially to the porphyrazine planes at Fe–Cbenzene distances of 3.435–3.725 Å and 3.352–3.669 Å for 7 and 8, respectively. The short distances suggest an interaction between the iron sites and the benzene π-system which is stronger in the case of the FeIV[double bond, length as m-dash]C[double bond, length as m-dash]FeIV unit with a higher Lewis acidity. The Fe–X–Fe angle increases in the sequence 678 from 158.52° to 168.5° and 175.10°, respectively, in agreement with the Fe–X bond order. However, the lengths of the Fe–X bonds do not follow this trend: Fe–O = 1.75/1.76 Å > Fe–C = 1.67/1.67 Å > Fe–N = 1.65/1.66 Å indicating unexpectedly long Fe–C bonds. This observation can be explained by back π-donation from the μ-carbido ligand to the Fe–C antibonding orbital thus decreasing the bond order which is confirmed by DFT calculations.

Graphical abstract: Synthesis and characterization of μ-nitrido, μ-carbido and μ-oxo dimers of iron octapropylporphyrazine

Supplementary files

Article information

Article type
Paper
Submitted
17 Oct 2014
Accepted
04 Dec 2014
First published
08 Dec 2014

Dalton Trans., 2015,44, 2240-2251

Synthesis and characterization of μ-nitrido, μ-carbido and μ-oxo dimers of iron octapropylporphyrazine

C. Colomban, E. V. Kudrik, D. V. Tyurin, F. Albrieux, S. E. Nefedov, P. Afanasiev and A. B. Sorokin, Dalton Trans., 2015, 44, 2240 DOI: 10.1039/C4DT03207A

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