Carbene complexes. Part 12. Electron-rich olefin-derived neutral mono- and bis-(carbene) complexes of low-oxidation-state manganese, iron, cobalt, nickel, and ruthenium
- 1 January 1977
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in J. Chem. Soc., Dalton Trans.
- No. 21,p. 2172-2180
- https://doi.org/10.1039/dt9770002172
Abstract
The electron-rich olefin [:[graphic omitted]R]2(LR 2; R = Me or Et) provrdes a ready source of various thermally stable neutral mono- and bis-(carbene) complexes of Fe, Ru, Co, and Ni and, with greater difficulty, of MnI. Noteworthy is the range of co-ordination numbers, formal metal oxidation states, and geometries (tetrahedral, square planar, trigonal bipyramidal, or octahedral) of the complexes. Amongst the 29 new complexes are the novel neutral bis(carbene) specres [Fe(LMe)2(NO)2], [Co(CO)(LEt)2(NO)], trans-[Fe(CO)3(LMe)2], [Ni(CO)2(LEt)2], [Fe(CO)2l2(LMe)2], and [Ni(LMe)2(NO3)2]; the last is the only diamagnetic nickel(II) dinitrate. Infrared spectra show that ν(CO) is low compared with analogous (e.g. phosphine) complexes: ν(CN2) is in the range 1 480–1 540 cm–1, the upper end being characteristic of the higher-oxidation state metal complexes. This trend is also observed in 13C n.m.r. chemical shifts when Ccarb. moves to higher field (Ccarb. is generally 200–230 p.p.m. downfield from SiMe4); [Ru3(CO)11 LEt] shows only one CO resonance, an indication of fluxionality, whereas [Fe2(CO)(µ-CO)2(η-C5H5)LEt] exists at 25 °C in solution as a mixture of cis and trans isomers.Keywords
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