Halogenated triphenylgallium and -indium in frustrated Lewis pair activations and hydrogenation catalysis

Abstract

The Lewis acids Ga(CF), In(CF) and Ga(CCl) are prepared and their Lewis acidity has been probed experimentally and computationally. The species Ga(CF) and In(CF) in conjunction with phosphine donors are shown to heterolytically split H and catalyse the hydrogenation of an imine. In addition, frustrated Lewis pairs (FLPs) derived from Ga(CF) and In(CF) and phosphines react with diphenyldisulfide to phosphoniumgallates or indates of the form [BuPSPh][PhSE(CF)] and [BuPSPh][(μ-SPh)(E(CF))] (E = Ga, In). The potential of the FLPs based on Ga(CF), In(CF) and Ga(CCl) and phosphines is also shown in reactions with phenylacetylene to give pure or mixtures of the products [BuPH][PhCCE(CX)] and RP(Ph)C=C(H)E(CX) A number of these species are crystallographically characterized. The implications for the use of these species in FLP chemistry are considered.This article is part of the themed issue 'Frustrated Lewis pair chemistry'.

Reactivity of a P–H Functionalized Al/P‐Based Frustrated Lewis Pair – Hydrophosphination versus Classic Adduct Formation

“…P–H ··· O distances below 300 pm were detected in few structurally authenticated compounds but their significance and energetic contribution is not clear . P–H ··· X hydrogen bonding has been found in FLP adducts with hydrogen halides ( X = F – I)[15b], and has been confirmed by a characteristic downfield shift of the P–H resonances in the 1 H NMR spectra to δ > 9 ppm. Al–C bond lengths increase significantly relative to the starting material (Table ) which is consistent with the increased coordination number at aluminum.…”

Frustrated Lewis pair chemistry

“…Gowda & Chen [7] apply FLPs in selective polymerizations of butyrolactones. Gabbaï and co-workers [8] report on efforts to combine carbon-Lewis acids with phosphines, while Stephan and co-workers [9] describe the use of gallium and indium Lewis acids in FLP chemistry. The issue is concluded with an article by Ashley and co-workers [10] in which they describe the activation of H 2 by a tin-based Lewis acid.…”

Structural and Energetic Features of Group 13 Element Trispentafluorophenyl Complexes with Diethyl Ether

“…[12][13][14] Strong Lewis acidity of E(C 6 F 5 ) 3 (E = Al, Ga, In) manifests itself in complexes with toluene. [15,16] After the discovery of activation of molecular hydrogen by frustrated Lewis pairs (FLP) based on B(C 6 F 5 ) 3 , [17,18] the FLP chemistry of group 13 trispentafluorophenyl derivatives re-tions of the compounds have been computed using three DFT methods. The 1 H NMR α-proton chemical shifts for the coordinated ether in deuteriobenzene and in CD 2 Cl 2 solutions correlate with gas phase dissociation enthalpies of the complexes.…”

“…The calculated and experimental Lewis acidity orders for E(C 6 F 5 ) 3 (E = B, Al, Ga, In) are not consistent. The calculated fluoride ion affinity (FIA) values for E(C 6 F 5 ) 3 decrease in order Al > B > Ga > In [16] or Al > Ga > B. [5] The Gutmann-Beckett method, [24,25] based on the 31 P NMR shift of Et 3 PO complexes, gives Lewis acidity order B > In > Ga. [16,26] The most consistent computational data, benchmarked with respect to high level ab initio computations, indicate that according to FIA (in kJ mol -1 ), boron compounds are less Lewis acidic compared to their Al analogs, and Lewis acidity changes nonmonotonically B (452) < Al (536) > Ga (453).…”

“…In light with the fact that molecular hydrogen activation can be achieved using B(C 6 F 5 ) 3 -Et 2 O FLP, [33] diethyl ether was chosen as a reference Lewis base for this study. The solid-state structures of boron B(C 6 F 5 ) 3 •Et 2 O [34,35] and gallium Ga(C 6 F 5 ) 3 • Et 2 O [16] derivatives are known. In this work we report the synthesis, crystal structures and thermal stability of complexes of group 13 element trispentafluorophenyl derivatives E(C 6 F 5 ) 3 (E = B, Al, Ga, In) with diethyl ether.…”