Synthesis, Structures, and Reactivity of Yttrium Alkyl and Alkynyl Complexes with Mixed TpMe2/Cp Ligands

The structurally characterized TpMe2-supported rare earth metal monoalkyl complex (TpMe2)­CpYCH2Ph­(THF) (1) was synthesized via the salt-metathesis reaction of (TpMe2)­CpYCl­(THF) with KCH2Ph in THF at room temperature. Treatment of 1 with 1 equiv of PhCCH under the same conditions afforded the corresponding alkynyl complex (TpMe2)­CpYCCPh­(THF) (2). Complex 1 exhibits high activity toward carbodiimides, isocyanate, isothiocyanate, and CS2; treatment of 1 with such substrates led to the formation of a series of the corresponding Y–C­(benzyl) σ-bond insertion products (TpMe2)­CpY­[(RN)2CCH2Ph] (R = iPr­(3a), Cy­(3b), 2,6-iPr–C6H3(3c)), (TpMe2)­CpY­[SC­(CH2Ph)­NPh] (4), (TpMe2)­CpY­[OC­(CH2Ph)­NPh] (5), and (TpMe2)­CpY­(S2CCH2Ph) (6) in 40–70% isolated yields. Carbodiimides and isothiocyanate can also insert into the Y–C­(alkynyl) σ bond of 2 to yield complexes (TpMe2)­CpY­[(RN)2CCCPh] (R = iPr­(7a), Cy­(7b)) and (TpMe2)­CpY­[SC­(CCPh)­NPh] (9). Further investigation results indicated that 1 can effectively catalyze the cross-coupling reactions of phenylacetylene with carbodiimides. However, treatment of o-allylaniline with a catalytic amount of 1 gave only the benzyl abstraction product (TpMe2)­CpY­(NHC6H4CH2CHCH2-o)­(THF) (10), without observation of the expected organic hydroamination/cyclization product. All of these new complexes were characterized by elemental analysis and spectroscopic properties, and their solid-state structures were also confirmed by single-crystal X-ray diffraction analysis.