114636-09-8Relevant articles and documents
Chromium tricarbonyl facilitated nucleophilic aromatic substitution by metal carbonyl anions: The synthesis and molecular structure of a new class of bimetallic π-arene complexes
Heppert, Joseph A.,Morgenstern, Mark A.,Scherubel, Devin M.,Takusagawa, Fusao,Shaker, Mohammad R.
, p. 1715 - 1723 (2008/10/08)
The highly nucleophilic metal carbonyl anions [CpFe(CO)2]- and [(C5Me5)Fe(CO)2]- (C5Me5 ≡ Cp*) react with (η-XRC6H4)Cr(CO)3 substrates in a previously unknown type of nucleophilic aromatic substitution to form (η6-{CpFe(CO)2}RC6H4)Cr(CO) 3 products. A variety of less reactive metal nucleophiles, including [CpMo(CO)3]-, [CpNi(CO)]-, [Mn(CO)5]-, and [Co(CO)4]-, fail to participate in the substitution reactions. The structure of (η-{CpFe(CO)2}ClC6H4)Cr(CO)3 has been determined by X-ray crystallography. The compound crystallizes in the space group P21/n with four molecules in the unit cell of dimensions a = 7.969 (2) A?, b = 18.982 (4) A?, c = 10.789 (2) A?, and β = 91.45 (3). Full-matrix least-squares refinement yielded R = 0.0353 for 2153 reflections. The structure shows that the conformation of the Cr(CO)3 fragment is determined by a cogging of the carbonyl ligands of the CpFe(CO)2 and Cr(CO)3 units to avoid steric interactions, although 1H and 13C NMR studies failed to show a perceptible barrier to Cr(CO)3 rotation about the Cr-Phcentroid vector. Certain haloarene substrates react predominantly through an apparent electron-transfer pathway to produce [CpFe(CO)2]2 and (η-RC6H5)Cr(CO)3. The fraction of reduced products formed is dependent on (1) the reducing power of the anion ([Cp*Fe(CO)2]- ? [CpFe(CO)2]-), (2) the electron-donating ability of the R group (electron donor ? electron acceptor), (3) the substitution pattern of the arene (in general ortho ? meta ? para), and (4) the identity of the halogen leaving group (I ? Cl > F).
