404835-14-9Relevant academic research and scientific papers
Allenylidene iron(II) complexes and their deprotonation, nucleophilic addition reactions, and cathodic protonation toward alkynyl derivatives: A chemical and electrochemical study
Venancio, Ana I.F.,Da Silva, M. Fatima C. Guedes,Martins, Luisa M.D.R.S.,Da Silva, Joao J.R. Frausto,Pombeiro, Armando J.L.
, p. 4654 - 4665 (2008/10/09)
The allenylidene complexes trans-[FeBr(=C=C=CRR′)(depe) 2][Y] (R = Me, R′ = Ph, 1; R = R′ = Ph, 2; R = R′ = Et, 3; depe = Et2PCH2CH2PEt2; Y = BF4, BPh4) were obtained by reaction of trans-[FeBr 2(depe)2] with the appropriate alkynol HC≡CCRR′(OH), in MeOH and in the presence of Na[BF4] or Na[BPh4]. Deprotonation of 3 or nucleophilic γ-addition to 2 led to the neutral enynyl and alkynyl complexes trans-[FeBr{-C≡CC(=CHMe) Et}-(depe)2] (4) and trans-[FeBr(-Ca≡CCPh2R″) (depe)2] (R″ = CN (5a), MeO (5b)), respectively. Complex 2 (Y = BPh4) also leads to the cationic alkynyl compounds trans-[Fe(NCMe){-C≡ CCPh2(X)}(depe)2][BPh 4] (X = NMe2 (6a), NHMe (6b)) and trans-[Fe(NCMe){- C≡CCPh2-(PMe3)}(depe)2]Y2 (Y2 = [BPh4]2 (7a), [BPh4] 2-xBrx (7b)), in acetonitrile solution, upon reaction with NHMe2, NH2Me, and PMe3, respectively. The complexes have been characterized by multinuclear NMR and IR spectroscopy, FAB-MS, and elemental analysis and, in the cases of 5a and 6a, also by X-ray diffraction analysis. Controlled-potential electrolysis of 2 yields the alkynyl species trans-[FeBr{-C≡CCPh2(H)}(depe)2] (8) via a 2e-/H+ process, and the oxidation potential of the complexes, measured by cyclic voltammetry, has allowed us to estimate the electrochemical Pickett (PL) and Lever (EL) ligand parameters for the cumulenic ligands. These are then ordered (together with related ligands) according to their net π-electron acceptor minus σ-donor ability as follows: carbynes > aminocarbyne > CO > vinylidenes > aryl allenylidene > alkyl allenylidene > NCR ? phosphonium alkynyl > cyanoalkynyl, Br, NCO → alkynyl, enynyl, aminoalkynyl.
Allenylidene and derived alkynyl complexes of iron(II) with the {FeBr(Et2PCH2CH2PEt2) 2}+ centre
Venancio, Ana I.F.,Martins, Luísa M.D.R.S.,Pombeiro, Armando J.L.
, p. 315 - 321 (2007/10/03)
The allenylidene complexes trans-[FeBr{=C=C=C(R)Ph}(depe)2] [BPh4] (depe=Et2PCH2CH2 PEt2; R=Me 1, Ph 2) were obtained by treatment of a methanolic solution of trans-[FeBr2(depe)2] with the appropriate alkynol HC≡C-C(R)Ph(OH), in the presence of Na[BPh4]. The methylallenylidene ligand in 1 undergoes reversible deprotonation (by NaOMe) to yield the enynyl (or ene-yne) complex of iron(II), trans-[FeBr{-C≡C-C(= CH2)Ph}(depe)2] 3. The diphenylallenylidene ligand in 2 undergoes regioselective hydride γ-addition on reaction with K[B{CH(Me)Et}3H] to afford the alkynyl complex trans-[FeBr {-C≡C-C(H)Ph2}(depe)2] 4.
