Evidence for a kinetic FLP reaction pathway in the activation of benzyl chlorides by alkali metal-phosphine pairs.

Kinetic frustrated Lewis pairs (FLP) allow facile cleavage of a number of E-H bonds (E = H, Si, C, B) where both the Lewis base and Lewis acid are involved in the bond activation transition state. More recently, kinetic FLP systems have been extended to the cleavage of C-X (X = F, Cl, Br) bonds. We report on the role of sodium tetrakis(pentafluorophenyl)borate in the benzylation of triarylphosphines, where the sodium cation and phosphine support a kinetic FLP type transition state.

Gauging the donor strength of iron(0) complexes their N-heterocyclic carbene gold(I) adducts.

We isolate and characterize the gold(I)-iron(0) adducts [(Pr-bimy)Au-Fe(CO)(PMe)][BAr] and [Au-{Fe(CO)(PMe)}][BAr] (Pr-bimy = 1,3-diisopropylbenzimidazolin-2-ylidene, BAr = tetrakis(pentafluorophenyl)borate). DFT analysis reveals that the gold-iron interaction in [(Pr-bimy)Au-Fe(CO)(PMe)][BAr] is predominantly a σ-donation from iron to gold. We further extend this class of compounds to include [(Pr-bimy)Au-Fe(CO)(PR)][BAr] (PR = PPh, PCy, PCyPh, PMePh, PMePh, P(4-CHF)) and [(Pr-bimy)Au-Fe(CO)(PPh)][BAr] and correlate the Pr-bimy carbenic C NMR signal with the relative donor strength of the iron(0) ligand.

Alkali Metal Adducts of an Iron(0) Complex and Their Synergistic FLP-Type Activation of Aliphatic C-X Bonds.

We report the formation and full characterization of weak adducts between Li and Na cations and a neutral iron(0) complex, [Fe(CO)(PMe)] (), supported by weakly coordinating [BAr] anions, [·M][BAr] (M = Li, Na). The adducts are found to synergistically activate aliphatic C-X bonds (X = F, Cl, Br, I, OMs, OTf), leading to the formation of iron(II) organyl compounds of the type [FeR(CO)(PMe)][BAr], of which several were isolated and fully characterized. Stoichiometric reactions with the resulting iron(II) organyl compounds show that this system can be utilized for homocoupling and cross-coupling reactions and the formation of new C-E bonds (E = C, H, O, N, S).