Water- and oxygen-sensitive compounds of the type R ’nEHal3-n (R' = SitBu2Ph; E = Triel) with or without donors, viz. RAlBr2, R'3Al, R'GaCl2'THF, R'GaCl2, R'3Ga, R'InCl2·THF and R'3In have been synthesized by reaction of EX3 with NaSitBu2Ph (prepared for this purpose) in the absence or presence of donors. The dihalides R'EHal2 have also been obtained by reaction of R'3E with EHal3, whereas monohalides R'2EHal are not accessible via these and other routes up to date. All trielanes have been characterized by NMR and the structures of the R'3E compounds have been determined by X-ray analyses.