Selective C–C bond formation at diiron μ-aminocarbyne complexes †

Synthesis, Characterization and Reactivity of New (μ‐Aminocarbyne)diruthenium Complexes Containing Alkynylimino Ligands

“…One CO ligand in the diruthenium aminocarbyne complexes [Ru 2 {µ-CN(Me)(R)}(µ-CO)(CO) 2 (Cp) 2 ] ϩ [R ϭ Xy, 1a; CH 2 Ph (Bz), 1b; Me, 1c] [11] can be easily replaced by Me 3 CCN after treatment with Me 3 NO in THF and a slight excess of the nitrile compound (Scheme 1). The resulting complexes [Ru 2 {µ-CN(Me)(R)}(µ-CO)(CO)(NCCMe 3 )- (Cp) 2 ] ϩ (R ϭ Xy, 2a; Bz, 2b; Me, 2c), obtained in good yields (85Ϫ88%), have been spectroscopically characterized.…”

Reactions of diiron mu-aminocarbyne complexes containing nitrile ligands

“…12 Proton abstraction from coordinated acetonitrile is not surprising, and its enhanced acidity has been exploited to catalyse MeCN condensation with carbonyl compounds. 13 However the rearrangement to cyanomethyl ligand is rather unusual and has been previously observed only in the case of [RhOs(CH 2 CN) (CO) 3 13 C NMR spectra show two signals of the same intensity for the nonequivalent Cp groups (for 7a at δ 5.01, 4.85 and 89.0 87.5, respectively). Likewise each of the N-bonded methyl groups in 7a gives rise to a singlet resonance.…”

“…The NMR spectra of 7b, which contain the asymmetrically substituted µ-C=N(Me)(CH 2 Ph) show the presence of two isomers in solution. These isomeric forms, which are usually found in complexes of the type [Fe 2 {µ-CN(Me)R}(µ-CO)(CO) (L)(Cp) 2 ] and indicated as α and β isomers, 3,10,11,15 are due to the different orientations of R and Me with respect to the non equivalent Fe atoms (Figure 1). Compound 7c consists of only one of the two possible α and β isomers.…”

“…8 Both chloride and bromide complexes show the presence, in CDCl 3 solution, of only the cis isomer as usually found in di-iron µ-aminocarbyne complexes 3,11 (cis and trans are referred to the mutual position of the Cp rings with respect to the Fe-Fe bond). By contrast, the iodide complex 3b consists of both cis and trans isomers, possibly due to bulkiness of the iodide ligand.…”

“…2 In recent years we have found that the formation of C-C bond in bridging aminocarbyne complexes [Fe 2 {µ-CN(Me)R}(µ-CO)(CO) 2 (Cp) 2 ][SO 3 CF 3 ] (R = Me, 1a; CH 2 Ph; 1b; Xyl, 1c) (Xyl = 2,6-Me 2 C 6 H 3 ) can be achieved by addition of carbon nucleophiles (R' -) which occurs selectively at different ligands: organocuprates and acetylides attack the carbonyl carbon to form the acyl complexes [Fe 2 {µ-CN(Me)R}(µ-CO)(CO)(COR')(Cp) 2 ], whereas organolithium or Grignard reagents give preferentially addition to the C 5 H 5 ring yielding the dienyl complexes [Fe 2 {µ-CN(Me)R}(µ-CO)(CO) 2 (Cp)(C 5 H 5 R')]. 3 Surprisingly, none of the above nucleophilic additions involve the µ-C of the aminocarbyne ligand, which appears rather unreactive, particularly if compared with the powerful electrophilic character of the µ-methylidyne carbon in the related complex [Fe 2 (µ-CH)(µ-CO)(CO) 2 (Cp) 2 ] + . 4 Only cyanide (from NBu 4 CN) has been found to react at the carbyne carbon to yield the aminocarbene 903 Reactions of Diiron µ-Aminocarbyne Complexes Containing Nitrile Ligands Vol.…”