In Situ Catalysts for the Intramolecular Hydroamination of Aminoalkynes – What Ligand Properties Determine Catalyst Activity?

Abstract

Insight into the iridium(I)/rhodium(I)-catalyzed hydroamination of 4-pentyn-1-amine was established through comparison of catalysts formed in situ from metal precursors and selected ligands with analogous catalysts which had been synthesized and isolated as pure complexes. The isolated metal complexes used were [Rh(bim)(CO) 2 ]BPh 4 (1) and [M(bpm)-(CO) 2 ]BPh 4 (2 M = Rh, 3 M = Ir), which contain the bidentate nitrogen donor ligands bis(1-methylimidazol-2-yl)methane (bim, 4) and bis(1-pyrazolyl)methane (bpm, 5). The metal precursors used for

Cationic Rh and Ir complexes containing bidentate imidazolylidene–1,2,3-triazole donor ligands: synthesis and preliminary catalytic studies

“…Rh(I)/Rh(III) and Ir(I)/Ir(III) complexes have been demonstrated by us and others to be efficient catalysts for this transformation. 12,20,32,[40][41][42][43][44][45][46][47][48] We have found that small variations in donor ability of the ligands can lead to significant variations in the catalytic efficiency of the resulting metal complexes. 32,41,49 We tested a number of the Rh(I), Rh(III) and Ir(III) complexes containing the NHC-1,2,3-triazolyl donor ligands described here as catalysts for the intramolecular hydroamination of 4-pentyn-1-amine to form 2-methyl-1-pyrroline (Table 3).…”

“…The catalytic results obtained in this work appear to confirm the general trend that complexes with ligands with more basic donors that bind more strongly to the metal centre are less active catalysts for the hydroamination reaction. 40 Rh(III) and Ir(III) complexes (4a, 4d and 5c, entries 5-7, Table 3) were not very efficient as catalysts for this hydroamination reaction possibly due to the fact that these complexes are coordinately saturated. We recently demonstrated that similar Ir(III) complexes with bidentate N-N or N( pyrazolyl)-NHC donor ligands in the presence of AgBF 4 could efficiently promote the intramolecular hydroamination of aminoalkynes.…”

Easy Entry into Reduced Ar‐BIANH2 Compounds: A New Class of Quinone/Hydroquinone‐Type Redox‐Active Couples with an Easily Tunable Potential

“…Compounds of the family bis(aryl)acenaphthenequinonediimine (Ar‐BIAN) ( 1 ; see Scheme ) have been known for some time,1–3 but have been brought to the general attention only in the 90s by Elsevier and his group 4. Since then, they have found widespread use mostly as ligands for transition metals and the corresponding complexes have been employed as catalysts for a wide variety of reactions, such as alkene hydrogenation,5 polymerization,6–11 copolymerization,12–18 aziridination,19 cyclopropanation,19 and epoxidation20 alkene‐CO copolymerization,21–24 alkyne coupling in the presence of halogens or organic halides and tin compounds25–27 or just tin compounds,28 selective semihydrogenation of alkynes29 and allenes,30 allylic aminations of olefins by nitroarenes in the presence of CO,31–33 the synthesis of pyrroles and oxazines from dienes, nitroarenes and CO,34 the reduction of nitroarenes to anilines by CO/H 2 O,35–37 the hydroamination of alkynes,38 the homo‐coupling of organic halides39 and their cross‐coupling reaction with organomagnesium, ‐zinc, and ‐tin reagents,40–44 the Suzuki–Miyaura cross coupling,45 the synthesis of 4‐quinolones and 2,3‐dihydroquinolones from 2′‐nitrochalcones and CO,46, 47 the synthesis of indoles from o ‐nitrostyrenes and CO,47, 48 the Heck arylation of olefins,49, 50 and oxidative Heck reaction,51, 52 the synthesis of dihydrofurans and dihydrobenzoxepines53 and N ‐acyl vinilogous carbamic acids,54 the cyclotrimerization of alkynes,55 the click reaction,56 the dimerization of vinyl ethers to acetals,57 and the diboration of α,β‐unsaturated carbonyl compounds 58. For some of these syntheses, the use of the Ar‐BIAN ligands was instrumental in achieving a high performance of the catalytic system.…”

Synthesis, UV–Vis and CV properties of a structurally related series of bis(Arylimino)acenaphthenes (Ar‐BIANs)

“…Bis(arylimino)acenaphthenes (Ar‐BIANs) are a class of compounds that have been frequently used as sterically bulky diimine ligands. Since the first accounts by Elsevier and van Asselt in the 1990s, numerous transition metal Ar‐BIAN complexes, wherein the Ar‐BIAN acts as a neutral bidentate chelate, have been reported, many of which have been employed in catalysis and olefin polymerization . Their coordination chemistry to main group, transition metals and lanthanides has also been widely explored .…”