110418-11-6Relevant articles and documents
Alkyl and η2-acyl complexes of iron(II)
Cardaci, Giuseppe,Bellachioma, Gianfranco,Zanazzi, Pierfrancesco
, p. 172 - 180 (2008/10/08)
The reduction with sodium amalgam in acetonitrile (MeCN) of [Fe(CO)2L2X2] (X = Cl, Br, I; L = PMe3, PMe2Ph,P(n-Bu)3, PMePh2, P(i-Bu)3, P(i-Pr)3, PEtPh2, PPh3) gives a mixture of two different complexes in equilibrium. One is probably the cluster complex [Fe(CO)2L2]3, isoelectronic with [Fe3(CO)12]; the other is the complex [Fe(CO)2L2(MeCN)]. The mixture in equilibrium reacts with RI (R = CH3, C2H6) to give oxidative addition products. With L = PMe3, PMe2Ph, and P(n-Bu)3 the products are the alkyl complexes [Fe(CO)2L2(R)I]. With L = PMePh2, PEtPh2, P(i-Bu)3, and PPh3 the reaction products are the η2-acyl complexes [Fe(CO)L2(η-COR)I]. Complex [Fe(CO)PMePh2)2(η2-COCH 3)I·2CH2Cl2] was analyzed by the single-crystal X-ray diffraction method. It crystallizes in the monoclinic space group P21/n with lattice parameters a = 23.603 (4) A?, b = 12.256 (3) A?, c = 12.318 (3) A?, and β = 97.08 (2)°; it contains four molecules per cell. The structure was solved by using 2642 observed reflections and refined to Rw = 0.062. The electronic and steric features of the phosphine ligands, which stabilize the η2-acyl structure, are discussed, the steric hindrance appearing to be the most important factor for the same metal. The effect of the nature of the metal is also discussed, the stability of the η2-acyl structure being correlated with the number of the d electrons on the metal in its formal oxidation state.