386702-89-2Relevant academic research and scientific papers
Phosphinoferrocene ureas: Synthesis, structural characterization, and catalytic use in palladium-catalyzed cyanation of aryl bromides
?koch, Karel,Císa?ová, Ivana,?těpni?ka, Petr
, p. 1942 - 1956 (2015/06/08)
Phosphinoferrocene ureas Ph2PfcCH2NHCONR2, where NR2 = NH2 (1a), NHMe (1b), NMe2 (1c), NHCy (1d), and NHPh (1e); the analogous thiourea Ph2PfcCH2NHCSNHPh (1f); and the acetamido derivative Ph2PfcCH2NHCOMe (1g) (Cy = cyclohexyl, fc = ferrocene-1,1′-diyl) were prepared via three different approaches starting from Ph2PfcCH2NH2·HCl (3·HCl) or Ph2PfcCHO (4). The reactions of the representative ligand 1e with [PdCl2(cod)] (cod = cycloocta-1,5-diene) afforded [PdCl(μ-Cl)(1e-κP)2]2 or [PdCl2(1e-κP)2]2 depending on the metal-to-ligand stoichiometry, whereas those with [PdCl(η3-C3H5)]2 and [PdCl(LNC)]2 produced the respective bridge cleavage products, [PdCl(η3-C3H5)(1e-κP)] and [PdCl(LNC)(1e-κP)] (LNC = [(2-dimethylamino-κN)methyl]phenyl-κC1). Attempts to involve the polar pendant in coordination to the Pd(II) center were unsuccessful, indicating that the phosphinoferrocene ureas 1 bind Pd(II) preferentially as modified phosphines rather than bifunctional donors. When combined with palladium(II) acetate, the ligands give rise to active catalysts for Pd-catalyzed cyanation of aryl bromides with potassium hexacyanoferrate(II). Optimization experiments revealed that the best results are obtained in 50% aqueous dioxane with a catalyst generated from 1 mol % of palladium(II) acetate and 2 mol % of 1e in the presence of 1 equiv of Na2CO3 as the base and half molar equivalent of K4[Fe(CN)6]·3H2O. Under such optimized conditions, bromobenzenes bearing electron-donating substituents are cyanated cleanly and rapidly, affording the nitriles in very good to excellent yields. In the case of substrates bearing electron-withdrawing groups, however, the cyanation is complicated by the hydrolysis of the formed nitriles to the respective amides, which reduces the yield of the desired primary product. Amine- and nitro-substituted substrates are cyanated only to a negligible extent, the former due to their metal-scavenging ability.
Selective borane reduction of phosphinoferrocene carbaldehydes to phosphinoalcohol-borane adducts. the coordination behaviour of 1-(diphenylphosphino)- 1′-(methoxymethyl)ferrocene, a new ferrocene O,P-hybrid donor prepared from such an adduct
Stepnicka, Petr,Cisarova, Ivana
, p. 3373 - 3389 (2013/04/10)
The reduction of ferrocene phosphino-aldehydes, R2PfcCHO (R = Ph, 2; Cy, 3; fc = ferrocene-1,1′-diyl, Cy = cyclohexyl) and (S p)-[Fe(η5-C5H3-1-CHO-2-PPh 2)(η5-C5H5)] ((S p)-4), with BH3·THF or BH3· SMe2 in THF at 0 °C selectively afforded the corresponding phosphinoalcohol-borane adducts, R2PfcCH2OH·BH 3 (R = Ph, 5; Cy, 6) and (Sp)-[Fe(η5-C 5H3-1-CH2OH-2-PPh2) (η5-C5H5)]·BH3 ((S p)-7), in quantitative yields. In contrast, the reactions performed at elevated temperatures favoured the formation of methyl derivatives (e.g., Ph2PfcCH3·BH3 (8)) resulting from overreduction (deoxygenation). The crystal structures of 3, 5, (S p)-7, 8 and Cy2PfcBr (9) have been determined by single-crystal X-ray diffraction analysis. The crystal assemblies of adducts 5 and (Sp)-7 are built up by means of C-H...O contacts, O-H...HB dihydrogen bonds and other soft interactions but, surprisingly, not via the conventional O-H...O hydrogen bonds. Adduct 5 was smoothly deprotected to give the corresponding free phosphine, Ph2PfcCH 2OH (1), and was further used for the preparation of a hybrid phosphinoether ligand, Ph2PfcCH2OMe (11). The latter compound was studied as a donor for Group 8-10 metal ions and for Cu(i), whereupon the following complexes were isolated and structurally characterised: [(η6-p-cymene)RuCl2(11-κP)] (12*), [(η6-p-cymene)RuCl(11-κP)(MeCN)][SbF6] (13*), [RhCl(cod)(11-κP)] (cod = η2: η2-cycloocta-1,5-diene; 14), trans-[PdCl2(11-κP) 2] (trans-15*), [PdCl(μ-Cl)(11-κP)]2 (16*), cis- and trans-[PtCl2(11-κP)2] (cis-17 and trans-17*), and [Cu(CF3SO3-κO)(11- κP)(H2O)] (18) (the asterisk indicates that the crystal structure was determined). In all these compounds, ligand 11 behaves as a P-monodentate donor while its ether group remains uncoordinated. This probably reflects structural flexibility of 11 resulting from the presence of the methylene linker and also distinguishes 11 from its known, non-spaced analogue Ph2PfcOMe.
