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

Abstract

The Lewis acids Ga(C6F5)3, In(C6F5)3 and Ga(C6Cl5)3 are prepared and their Lewis acidity has been probed experimentally and computationally. The species Ga(C6F5)3 and In(C6F5)3 in conjunction with phosphine donors are shown to heterolytically split H2 and catalyse the hydrogenation of an imine. In addition, frustrated Lewis pairs (FLPs) derived from Ga(C6F5)3 and In(C6F5)3 and phosphines react with diphenyldisulfide to phosphoniumgallates or indates of the form [tBu3PSPh][PhSE(C6F5)3] and [tBu3PSPh][(μ-SPh)(E(C6F5)3)2] (E =Ga, In). The potential of the FLPs based on Ga(C6F5)3, In(C6F5)3 and Ga(C6Cl5)3 and phosphines is also shown in reactions with phenylacetylene to give pure or mixtures of the products [tBu3PH][PhCCE(C6X5)3] and R3P(Ph)C=C(H)E(C6X5)3. 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'.