Formation and Characterization of the Gallium and Indium Subhydride Molecules Ga₂H₂ and In₂H₂:  A Matrix Isolation Study

Abstract

Ga2 reacts spontaneously with H2 in solid Ar matrixes at 12 K to form the cyclic molecule Ga(mu-H)2Ga. In2 does not react with H2 under similar conditions, but irradiation at wavelengths near 365 nm induces the formation of the corresponding indium hydride, In(mu-H)2In. The molecules have been identified and characterized by the IR spectra displayed by matrixes containing the metal and H2, D2, HD, or H2 + D2; they each have planar, dihydrido-bridged structures with D2h symmetry, as endorsed by comparison of the measured spectra (i) with the properties forecast by quantum chemical calculations and (ii) with the spectra of known gallium and indium hydrides. Both are photolabile under visible light (lambda > 450 nm): green light (lambda = ca. 546 nm) causes Ga(mu-H)2Ga to isomerize to a mixture of HGaGaH and H2GaGa, whereas broad-band visible irradiation (lambda > 450 nm) of In(mu-H)2In gives rise to the isomer HInInH, together with InH. The isomerization can be reversed by UV photolysis (lambda = ca. 365 nm) of HGaGaH, H2GaGa, and HInInH or by near-IR photolysis (lambda > 700 nm) of HGaGaH and H2GaGa.

Characterization of Isolated Ga2 Molecules by Resonance Raman Spectroscopy and Variations of GaGa Bonding

“…[11] It has been shown subsequently, however, that the compound is better regarded as a Na 2 Ga 2 cluster and that the GaÀGa bond cannot adequately be described as a triple bond. [12,[13][14] Meanwhile, the neutral compound HGaGaH was characterized in matrix-isolation experiments, [15,16] and some derivatives RGaGaR (e.g. R = 2,4,6-iPr 3 C 6 H 2 ) [17] were structurally analyzed.…”

Molecular Dialane and Other Binary Hydrides

“…Very recently the subhydrides Ga 2 H 2 and In 2 H 2 were generated in argon matrices [19] and compared with the known subhydrides HBBH and Al(m-H) 2 Al. [20] In these experiments H 2 adds spontaneously to matrix-isolated Ga 2 units, deposited from gallium vapor (Scheme 2).…”

“…[21] In addition, Himmel et al reported a photochemically induced pathway to a further isomer: H 2 GaGa. [19] The fact that different isomers have been identified is due to the comparably small energy differences between them.…”

Molekulares Dialan und andere binäre Hydride

“…[4] Die Hydride des Aluminiums gehen auf Wiberg und Stecher zurück, die 1939 in elektrischen Entladungsreaktionen Trimethylaluminium mit Wasserstoff umsetzten und dabei eine Mischung der Hydridoalane R 3Àn AlH n erhielten. [5] Das [19] und den bereits bekannten Subhydriden HBBH und Al(m-H) 2 Al [20] zur Seite gestellt. H 2 addiert dabei spontan an matrixseparierte, aus Ga-Dampf erhaltene Ga 2 -Einheiten (Schema 2).…”

“…Die analoge Reaktion mit In 2 erfordert photolytische Bedingungen. [19] Es entstehen die Dimere Ga(m-H) 2 Ga und In(m-H) 2 …”