Highly Selective Bis(imino)pyridine Iron-Catalyzed Alkene Hydroboration

Abstract

Bis(imino)pyridine iron dinitrogen complexes have been shown to promote the anti-Markovnikov catalytic hydroboration of terminal, internal, and geminal alkenes with high activity and selectivity. The isolated iron dinitrogen compounds offer distinct advantages in substrate scope and overall performance over known precious metal catalysts and previously reported in situ generated iron species.

Catalytic Hydrogenation Activity and Electronic Structure Determination of Bis(arylimidazol-2-ylidene)pyridine Cobalt Alkyl and Hydride Complexes

“…The X-band EPR spectrum exhibits an isotropic signal ( g iso = 2.003) consistent with an S = 1/2 organic radical. As expected, the introduction of the predominantly nonmagnetic magnesium nucleus (90% 24/26 Mg, I = 0; 10% 25 Mg, I = 5/2) simplifies the data significantly producing a spectrum with a 14-line main feature and additional small signals visible at the edges of the spectrum arising from coupling to 25 Mg. Despite the smaller number of potential hyperfine lines (4050) the spectrum of MgBr[( iPr CNC)] covers a slightly wider field range, which is most likely due to small changes in the spin distribution over the π-system induced by Mg as compared to Na resulting in slightly different coupling constants for the N and H nuclei.…”

Phosphine-Iminopyridines as Platforms for Catalytic Hydrofunctionalization of Alkenes

“…30 The ligand PN Ph py derived from 2-benzoylpyridine was particularly well-behaved and afforded 1:1 complexes with iron dihalides. As for related FeX 2 L 3 species (L 3 = tridentate ligand), 5,[25][26][27]29,31 the complex FeX 2 (PN Ph py) is a precursor to a highly active catalyst for hydrosilylation and hydroboration of alkenes. An unstable catalytically active hydride intermediate was detected, and further work is aimed at characterization of related species with other ligand platforms.…”

Iron Catalysis II

“…The reaction is chemoselective as only terminal C¼C bond of a polyene is hydroborated [207]. Simultaneously, Chirik reported that the bis(imino)pyridine iron dinitrogen complex C9 (1 mol%) was also efficient for the hydroboration of terminal and disubstituted alkenes under neat conditions at 25 C for 15 min to 24 h. Notably, the reaction also succeeded regioselectively with styrene derivatives [208]. Using a similar system, generating the active catalyst from the dichloro-iron complex C87 or from FeCl 2 and the corresponding bis-iminopyridine ligand 4 (1 mol%) and EtMgBr (3 mol%), hydroboration of functional alkenes can be efficiently performed at rt for 1 h using 1.1 equiv.…”