The fundamental reactivity of amorphous [YMe3](n) was representatively examined: toward GaMe3 as a Lewis acid, 9-fluorenone as a carbonyl substrate, and tetramethyldisilazane (HN(SiHMe2)(2)) as a Bronsted acid. The products obtained from the 3-equiv reactions were spectroscopically and X-ray crystallographically identified. Y(GaMe4)(3) shows Y---Ga distances of 3.0393(4) and 3.0502(3) angstrom, which are significantly shorter than the Y---Al distances in Y[AlMe4](3)[Al2Me6](0.5) (av 3.068 angstrom). The homoleptic alkoxide [Y(OC14H11)(3)](x) bearing sterically demanding 9-Me-fluorenoxy ligands documents high methyl group transfer economy via the 1,2-addition reaction of [YMe3](n) to 9-fluorenone; it was obtained in single-crystalline form in a minor byproduct, the asymmetric dimer [Y(OC14H11)(2)(mu-OC14H11)](2)(9-fluorenone). The previously elusive unsolvated complex {Y[N(SiHMe2)(2)](3)} also shows a dimeric molecular composition, {Y[N(SiHMe2)(2)](2)[mu-N(SiHMe2)(2)]}(2), featuring asymmetrically bridging silylamide ligands and Y---SiH multi-beta-agostic interactions in the solid state [(Y---Si)(min) 3.0521(7) angstrom, (Y---H)(min) 2.41(3) angstrom, nu(Si-H)(agostic) 1931 cm(-1)].
