Diiron μ-Vinyliminium Complexes from Acetylene Insertion into a Metal−Aminocarbyne Bond

Abstract

The complexes [Fe 2 {µ-CN(Me)(R)}(µ-CO)(CO)(NCMe)(Cp) 2 ][SO 3 CF 3 ] (R ) Xyl, 1a; R ) Me, 1b; R ) CH 2 Ph, 1c; Xyl ) 2,6-Me 2 C 6 H 3 ), containing a labile NCMe ligand, react under mild conditions with a variety of terminal alkynes HCtCR′ (R′) SiMe 3 , Me, Bu n , Tol, Ph, H; Tol ) 4-MeC 6 H 4 ) to give the bridging vinyliminium complexes [Fe 2 {µ-σ: 7). Insertion of the alkyne into the metal-carbyne carbon bond is regiospecific, resulting only in the product containing the R′ group on the carbon bound to Fe. Similarly, insertion of the disubstituted alkynes R′CtCR′ (R′ ) Me, Et) affords the analogous compounds [Fe 2 {µ-σ:). The molecular structure of complex 2a has been elucidated by an X-ray diffraction study.

Coupling of Allenes with μ‐Alkylidyne Ligands in Diiron Complexes: Synthesis of Novel Bridging Thio‐ and Aminobutadienylidene Complexes

“…The cationic complex 5a can be described as a vinyliminium cation, and all of its relevant bonding parameters perfectly parallel the ones described in the literature for analogous complexes (Scheme 2a). [10] In addition, the molecule displays a cis geometry for the Cp ligands, and the E conformation for the iminium group, as normally found for similar complexes that present a Me and a Xyl group at the iminium moiety and a hydrogen atom at C β . (2) is drawn.…”

“…The spectroscopic properties (IR and NMR spectra) of 5a,b closely resemble those reported for analogous vinyliminium species. [10] The NMR spectrum of 5a reveals the presence of two isomeric forms (E and Z isomers) that are attributable to the different orientations that the two N substituents can assume and that are due to the double-bond character of the C α -N (iminium) interaction. As expected, the E isomer, in which the Xyl group points far from the Fe atom, which corresponds to the structure found in the solid, prevails in solution with an E/Z ratio of 5:1).…”

“…Our interest in the transformation of bridging ligands has been concerned so far with the assembly of amino-and thiocarbyne ligands in the diiron complexes 1 and 2 with alkynes [10] and alkenes [11] (Scheme 2). The reaction of 1 with alkynes, which affords bridging vinyliminium complexes (a, Scheme 2), simply consists of the alkyne insertion in the metal-carbyne bond.…”

γ‐Deprotonation of Bridging Vinyliminium Ligands: New Route to Aminobutadienylidene Diiron and Diruthenium Complexes

“…[1] This is also the case for diiron vinyliminium complexes 1 [2] (Scheme 1), in which the bridging ligand undergoes transformations that are unusual for noncoordinated α,β-unsaturated iminium species. [3] As an example, µ-vinyliminium ligands undergo nucleophilic addition at the iminium carbon atom or at the adjacent α-C in place of the expected Michael-type conjugate addition (addition at the β position).…”

“…δ = 230, 60, and 210 ppm, respectively, which are values typical for a µ-vinyliminium ligand. [2] Moreover, the bridging CO is found at ca. δ = 235 ppm, whereas the acyl carbon atom resonates at δ = 220 ppm.…”