Phosphinite-Iminopyridine Iron Catalysts for Chemoselective Alkene Hydrosilylation

Abstract

A series of new pincer iron complexes with electron-donating phosphinite-iminopyridine (PNN) ligands has been prepared and characterized. These iron compounds are efficient and selective catalysts for the anti-Markovnikov alkene hydrosilylation of primary, secondary, and tertiary silanes. More importantly, the system exhibits unprecedented functional group tolerance with reactive groups such as ketones, esters, and amides. Furthermore, the iron-catalyzed alkene hydrosilylation was successfully applied to the synthesis of a valuable insecticide, silafluofen. The electronic properties and structures of the iron complexes have been studied by spectroscopies and computational methods. Overall, the iron catalysts may provide a low-cost and environmentally benign alternative to currently employed precious metal systems for alkene hydrosilylation.

Phosphine-Iminopyridines as Platforms for Catalytic Hydrofunctionalization of Alkenes

“…The blue solid exhibited low solubility in THF and dichloromethane, but good solubility in both MeOH and water. 2 ](BPh 4 ) 2 was prepared similarly from 6-methylpyridine-2-carboxaldehyde and identified crystallographically ( Figure 3). …”

“…Iron complexes of phosphonite-based PNN ligands exhibit high activity for hydrosilylation of unactivated alkenes even in the presence of carbonyl functional groups. 2,5 In a related study, a dialkylphosphinomethyl-bipyderived PNN platform supports highly active catalysts for hydroboration. 6 The present paper describes new iron complexes of PNN ligands that are hybrids of the aforementioned N−N−N and P−N−N systems.…”

Computational insights into the mechanism of iron carbonyl-catalyzed ethylene hydrosilylation or dehydrogenative silylation

“…In this regard, noteworthy efforts have been devoted to the development of efficient and selective reaction of hydrosilanes to olefins employing a wide variety of transition metals [3][4][5][6][7][8][9][10]. Since iron is much less expensive and environmentally friendly compared to other transition metals like Rh, Pt and Ru [11], iron-based catalysts for hydrosilylation have received considerable interests [12][13][14][15][16][17][18][19].…”

Iron‐Catalysed Hydrofunctionalisation of Alkenes and Alkynes

“…[99] Huang reported that structurally related, tridentate phosphinate-iminopyridine (PNN) iron complexes 188 were chemoselective catalysts for the hydrosilylation of alkenes 189 (Scheme 40). [100] A range of sterically differentiated (PNN)iron(II) chloride and bromide complexes were synthesised, characterised and applied as pre-catalysts in the hydrosilylation of terminal alkenes. Reduction of the iron(II) pre-catalyst in situ using NaHBEt 3 (2 equiv.…”