Inorganic Chemistry, Vol.59, No.23, 17488-17496, 2020
Synthesis of Silyl Aluminum Reagents: Relevance Toward Atomic Layer Deposition of Metal Silicides and the Serendipitous Synthesis of a Novel Al-Hydride Cluster
The novel mono-silyl [(R3Si)AlX2](2), di-silyl [(R3Si)(2)AlX](2), tri-silyl (R3Si)(3)Al center dot Et2O, and -ate-complex [(R3Si)(4)Al](4)center dot Li-9(Et2O)(2) have been synthesized by reaction of AlX3 (X = CI, Br) with silyl lithium reagents ((BuMe2SiLi)-Bu-t, Et3SiLi) in Et2O. Treatment of these compounds with Me3N yields the corresponding amine-coordinated silyl aluminum complexes (R3Si)ALX(2)center dot NMe3, (R3Si)(2)-AlX center dot NMe3, and (R3Si)(3)Al center dot NMe3. An intramolecular amine-coordinated mono-silyl aluminum complex Me2N-(CH2)(3)((BuMe2Si)-Bu-t)(2)SiAlCl2 was prepared by the reaction of Me2N(CH2)(3)((BuMe2SO2SiLi)-Bu-t with AlCl3 in Et2O. In addition, reaction of [((BuMe2SO2AlBr)-Bu-t](2) with LiAlH4 yields the novel aluminum hydride cluster [((BuMe2Si)-Bu-t)(2)Al(mu-H)AlH3](6) which upon addition of TMEDA yields the ion pair [(((BuMe2Si)-Bu-t)(2)AlH)(2)(mu-H)](-)[AlH2(TMEDA)(2)](+). The amine-coordinated di- and tri-silyl aluminum complexes possess higher thermal stability than the analogous etherate complexes and are reasonably volatile (100-140 degrees C, 0.2 Torr). The materials presented herein were analyzed via thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) to assess their viability as potential ALD precursors.