The Reactions of R2Ga−GaR2 and R2In−InR2 [R = CH(SiMe3)2] with Protic Reagents: Substituent Exchange versus Cleavage of the Element−Element Bond

Abstract

Tetrakis[bis(trimethylsilyl)methyl]digallane(4) (1) with a Ga−Ga single bond and the corresponding diindane(4) 2 with an In−In single bond were treated with different protic reagents: tert-Butyl alcohol did not react with 1 at all, while phenol gave a mixture of unknown products, which could not be separated. The more acidic pentafluorophenol did not react as an acid, but C−F bonds were cleaved to form almost quantitatively the dimer (R2GaF)2 5, which was characterized by a crystal-structure determination. Water and 1 yielded the dimeric dialkylgallium hydroxide 6. The Ga−Ga bond was also cleaved by the reaction of 1 with durylthiophenol (duryl = 2,3,5,6-tetramethylphenyl), which gave two main products: R2Ga(SDuryl) 7 and RGa(SDuryl)2 8. In contrast, the chelating acid dibenzoylmethane reacted by means of a substituent exchange, with the release of two equiv. of bis(trimethylsilyl)methane for each formula unit of 1, to form 9, in which the Ga−Ga bond is retained and each chelating 1,3-diphenyl-1,3-propanedionato ligand is in a terminal position bonded to only one Ga atom, in more than 80% yield. The Ga−Ga bond is shortened [244.1(1) pm] compared to that in the starting compound tetraalkyldigallane(4) 1. The In−In bond of diindane(4) 2 is, however, cleaved in a similar reaction with dibenzoylmethane, and only the fragmentation product dialkyl(1,3-diphenyl-1,3-propanedionato)indium 10 could be isolated.