Reactivity of allylphosphines with iridium complexes: Diallylphosphines as new bidentate ligands

Iridium Diphosphine Complexes Featuring Pendant Lewis Acids: Efforts toward Selective Heteroarene Borylation

“…Compounds with similar motifs have been reported [27,28] . Notwithstanding, this reactivity does differ from related iridium compounds bearing monophosphine allyl ligands, where C−H cyclometallation was witnessed [12,29] …”

“…[27,28] Notwithstanding, this reactivity does differ from related iridium compounds bearing monophosphine allyl ligands, where CÀ H cyclometallation was witnessed. [12,29] Notably, compound 7 is C 1 -symmetric, causing its 1 H NMR spectrum between 6.2 � δ H � 4.4 ppm and 3 � δ H � 0.9 ppm to appear convoluted (Scheme 4, Figure 2, and Supporting Information). By 1 H NMR spectroscopy, four multiplets at δ H = 6.07, 5.95, 5.82 and 5.…”

“…[11] Diphosphine ligand systems were chosen due to an ease in manipulation of both primary and secondary coordination sphere; iridium-phosphorus bonds are also known to be additionally robust and allow for facile probing using 31 P NMR spectroscopy. [12][13][14] Moreover, it has been shown that diphosphine ligands are viable candidates for iridium-catalysed arene and heteroarene borylation. [15][16][17] The ligand system of interest, 1,2-bis(di(3-dicyclohexylboraneyl)propylphosphino)ethane (P 2 B Cy 4 ) was previously reported by members of our team in 2020, and was shown to coordinate Lewis basic molecules, such as 4-N,N,-dimethylaminopyridine (DMAP) via its Lewis acidic secondary coordination sphere; this scaffold has also been used to assist in small molecule activation and transmetalation reactions using gold(I) pyridyl compounds.…”

“…We anticipated that this could be tested by first synthesizing an allyl‐substituted phosphine‐ligated iridium complex, which could then be hydroborated to create a phosphinoboranyl iridium complex [11] . Diphosphine ligand systems were chosen due to an ease in manipulation of both primary and secondary coordination sphere; iridium‐phosphorus bonds are also known to be additionally robust and allow for facile probing using 31 P NMR spectroscopy [12–14] . Moreover, it has been shown that diphosphine ligands are viable candidates for iridium‐catalysed arene and heteroarene borylation [15–17] .…”