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

The structurally characterized Tp(Me2)-supported rare earth metal monoalkyl complex (Tp(Me2))CpYCH2Ph(THF) (1) was synthesized via the salt-metathesis reaction of (Tp(Me2))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 (Tp(Me2))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) sigma-bond insertion products (Tp(Me2))CpY[(RN)(2)CCH2Ph] (R = Pr-i(3a), Cy(3b), 2,6-Pr-i-C6H3(3c)), (Tp(Me2))CpY[SC(CH2Ph)NPh] (4), (Tp(Me2))CpY[OC(CH2Ph)NPh] (5), and (Tp(Me2))CpY(S2CCH2Ph) (6) in 40-70% isolated yields. Carbodiimides and isothiocyanate can also insert into the Y-C(alkynyl) sigma bond of 2 to yield complexes (Tp(Me2))CpY[(RN)(2)CC CPh] (R = Pr-i(7a), Cy(7b)) and (Tp(Me2))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 (Tp(Me2))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.