Lewis-Acid-Assisted Methyl Exchange Reactions In Silylated Aminodichloroarsanes

Lewis-acid-assisted methyl/chlorine, methyl/azide, and methyl/triflate exchange reactions between silicon and arsenic centers have been studied and applied to different silylated aminoarsane species leading to a number of new methylarsane compounds: bis(trimethylsilyl)amino(dichloro)arsane (3) was reacted with GaCl₃ yielding a bis(chlorodimethylsilyl)-tetramethyl-cyclo-disilazane (4) accompanied by the release of Me₂AsCl, while trimethylsilyl(m-terphenyl)amino(dichloro)arsane (5) (m-terphenyl = 2,6-Mes₂-C₆H₃, Mes = 2,4,6-Me₃C₆H₂) reacted with GaCl₃ to give dichloromethylsilyl(m-terphenyl)aminodimethylarsane (6). In the presence of trimethylsilylazide, trimethylsilyl(m-terphenyl)amino(dichloro)arsane displays a methyl/azide exchange triggered by the action of GaCl₃ yielding azidodimethylsilyl(m-terphenyl)amino(chloro)methylarsane (7). Moreover, methyl/triflate exchange reactions have been observed in the reaction of trimethylsilyl(m-terphenyl)amino(dichloro)arsane (i) with 1 equiv of AgOTf (OTf = triflate) yielding N-(trifluoromethylsulfonatodimethylsilyl)-N-(m-terphenyl)amino(methyl)chloroarsane (8) and (ii) with 2 equiv of AgOTf yielding N-(trifluoromethylsulfonatodimethylsilyl)-N-(m-terphenyl)trifluoromethylsulfonatomethylarsane (9). All new compounds (3−9) have been fully characterized by means of vibrational spectroscopy, X-ray, CHN analysis, MS, and NMR studies. A possible reaction mechanism is discussed starting from an initial chloride abstraction and the intermediate formation of a cationic iminoarsane species. In a second step, a methyl shift from the silicon to the arsenic center occurs.