Reactivity of Rare Earth Metal Alkyl Complexes with Nitriles or Isonitrile: Versatile Ways toward Multiply Functionalized β-Diketiminato, (Iso)indolyl, and Imidazolyl Chelating Rare Earth Metal Complexes

The reactivity of the rare earth metal alkyl complexes LRE(CH2SiMe3)(THF)(2) (1(RE) ) [RE = Y (1 (Y) ), Yb (1(Yb) ), Lu (1(Lu) ); L = 2,5-[(2-pyrrolyl)-CPh2](2)(N-methyl-pyrrole)] with various nitriles and isonitriles has been fully developed. Treatment of the yttrium monoalkyl complex (1(Y) ) with 2 equiv of aromatic nitriles afforded the symmetric trisubstituted beta-diketiminato yttrium complexes (2(Y(H)) , 2(Y(Me)) , and 2(Y(F)) ) through successive cyano group insertion into the RE-C bond and 1,3-H shift or the unsymmetric trisubstituted beta-diketiminato yttrium complex (3(Y) ) unexpectedly via a 1,3-SiMe3 shift when 4-(trifluoromethyl)-benzonitrile was used in this reaction under the same conditions. By treating 1(Y) with 2 equiv of tolyl acetonitrile, an activation of the sp(3) C-H bond occurred to form the corresponding beta-aryl keteniminato complexes 4(Y( p -tol) )and 4(Y( m -tol)) . Remarkably, a heteroleptic cleavage of the CO-CN bond took place in the reaction of 1 Y with benzoyl nitrile, affording the unsymmetric trinuclear yttrium complex 5(Y) bridged by three cyanide groups. Dinuclear ytterbium and lutetium complexes 6(Yb) and 6 Lu containing a functionalized isoindole fragment were synthesized from the reactions of 1 with phthalonitrile by tandem insertion and cyclization. Further studies indicated that the temperature and stoichiometric ratio have a great influence on the reactivity patterns between the reactions of 1 RE with benzylisonitrile: two tetrasubstituted beta-diketiminato complexes 8 and 9 were obtained at -30 degree celsius, and tetrasubstituted imidazolyl yttrium and lutetium complexes 7 were isolated at elevated temperature, respectively. In addition, the tetrasubstituted beta-diketiminato complexes 8 and 9 could be irreversibly converted to the cyclization products 7 by elevating the reaction temperature not only on the NMR scale but also on the preparative scale. Notably, when the phenyl isonitrile instead of benzyl isonitrile was reacted with 1(Yb) , a 2,3-functionalized indolyl ytterbium complex 10(Yb) was isolated.