Convenient Access to Gallium(I) Cations through Hydrogen Elimination from Cationic Gallium(III) Hydrides

Abstract

Although gallium hydrides X n GaH 3−n (X = monoanionic substituent) are usually stable compounds, cationic arene-solvated species [H 2 Ga(arene) 2 ] + spontaneously eliminate dihydrogen at room temperature to afford the arene-solvated gallium(I) compounds [Ga(PhF) 2 ][CHB 11 Cl 11 ] (1) and [Ga-(Ph 3 CH)][B(C 6 F 5 ) 4 ] (3). A key requirement appears to be the presence of a weakly coordinating anion. Use of the more basic triflimide anion, [NTf 2 ] − , reverses the stability, i.e., the gallium(III) hydride H 2 GaNTf 2 ( 4) is more stable than the gallium(I) compound GaNTf 2 (5). The experimental results are supported by DFT calculations. Compounds 1 and 3 can be used as catalysts for the oligomerization of 2,4,4-trimethyl-1pentene and the hydrosilylation of benzophenone and 1-hexene.

The Coordination Chemistry and Clustering of Subvalent Ga+ and In+ upon Addition of σ‐Donor Ligands

“…Moreover, [Ga(PhF) 2 ][CHB 11 Cl 11 ] has been reported to initiate the hydrosilylation of benzophenone as well as 1-hexene. [71] Yet, nothing is known on the mechanism.…”

Insights into the Composition and Structural Chemistry of Gallium(I) Triflate

“…[Ga(arene) n ] + [Al(OC(CF 3 ) 3 ) 4 ] − ( n =2, 3) salts are well‐behaved sources of Ga I , but these anions are still not as widely used as simple weakly coordinating anions (WCAs) such as triflate [5] . More recently, Ga I species have been accessed via reductive elimination of H 2 from Ga III dihydrides [6] . Furthermore, a family of Ga‐based carbenoids, with differing charges and ring sizes, have emerged as important building blocks in low‐valent Ga chemistry and have been used as ligands in coordination chemistry [7]…”

“…There are a growing number of reports of Ga I involvement in catalysis and the development of new, more accessible, well‐behaved low‐valent gallium sources is particularly important to allow this area to grow. [Ga(arene) n ] + salts catalyze the polymerization of alkenes, [5e,f, 6] and have been shown to be active catalysts for cycloisomerization, transfer hydrogenation, and reductive hydroarylation reactions [9] . There is also evidence for Ga I involvement in important mechanistic steps that underpin many catalytic reactions, for example, reductive elimination, suggesting exciting possibilities for the Ga I /Ga III redox couple in other catalytic reactions [3c, 6] .…”

“…A toluene molecule in the lattice, disordered over two positions, is omitted for clarity. Selected bond lengths [] and angles[8]: Ga1-Ga1' 2.355(6), Ga2-C 6 Me 6 (cent) 2.525(9), Ga2-C 6 H 5 Me(cent) 2.813(11); C 6 (cent)-Ga2-C 6 (cent) 134.97-(30).…”

Insights into the Composition and Structural Chemistry of Gallium(I) Triflate

“…[5] More recently, Ga I species have been accessed via reductive elimination of H 2 from Ga III dihy-drides. [6] Furthermore, a family of Ga-based carbenoids, with differing charges and ring sizes, have emerged as important building blocks in low-valent Ga chemistry and have been used as ligands in coordination chemistry. [7] There are a growing number of reports of Ga I involvement in catalysis and the development of new, more accessible, well-behaved low-valent gallium sources is particularly important to allow this area to grow.…”