Small molecule activation by mixed methyl/methylidene rare earth metal complexes†
Abstract
Diverse reactivity patterns of mixed tetramethyl/methylidene rare-earth complexes bearing bulky benzamidinate coligands L3Ln3(μ2-Me)3(μ3-Me)(μ3-CH2) [L = [PhC(NC6H3iPr2-2,6)2]−; Ln = Y(1a), Lu(1b)] with PhCN, alkynes, and CS2 have been established. Reaction of complexes 1 with PhCN gave the μ3-CH2 addition complexes (NCNdipp)3Lu3(μ2-Me)3(μ3-Me)[μ–η1:η1:η3-CH2C(Ph)N] [Ln = Y(2a), Lu(2b)]. Treatment of complexes 1 with phenylacetylene afforded unexpected alkenyl dianion complexes L3Ln3(μ2-Me)3(μ3-Me)(μ–η1:η3-PhCCMe) [Ln = Y(3a), Lu(3b)] through the insertion of rare earth methylidene into a C–H bond in a reductive fashion. However, reaction of complexes 1 and HCCSiMe3 gave μ3-Me protonolysis complexes L3Ln3(μ2-Me)3(μ3-CCSiMe3)(μ3-CH2) [Ln = Y (4a), Lu (4b)] in excellent yields. Treatment of complexes 1 with CS2 led to the formation of the methyl activation complexes L3Ln3(μ2-Me)2(μ3-CH2)(μ3–η1:η2:η2-S2CCH2) [Ln = Y(5a), Lu(5b)]. All the new complexes were fully characterized.