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

Abstract

The reactivity of the rare earth metal alkyl complexes LRE(CH 2 SiMe 3 )(THF) 2 (1 RE ) [RE = Y (1 Y ), Yb (1 Yb ), Lu (1 Lu ); L = 2,5-[(2-pyrrolyl)CPh 2 ] 2 (N-methylpyrrole)] 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 βdiketiminato 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 β-diketiminato yttrium complex (3 Y ) unexpectedly via a 1,3-SiMe 3 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 β-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 β-diketiminato complexes 8 and 9 were obtained at −30 °C, and tetrasubstituted imidazolyl yttrium and lutetium complexes 7 were isolated at elevated temperature, respectively. In addition, the tetrasubstituted β-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 2,3functionalized indolyl ytterbium complex 10 Yb was isolated.

Ligand–Metal Complementarity in Rare-Earth and Actinide Chemistry

“…Further variables, such as the rate and order of precursor addition and the stoichiometry of the catalyst activator, were all found to influence the reaction significantly, but under the right conditions, a living polymerization reaction was achievable. Zhu and Wang’s team further explored the Lewis acid chemistry of rare earths by demonstrating the insertion of a range of nitrile and isonitrile molecules into metal–alkyl bonds in [RE­(L)­(CH 2 SiMe 3 )­(THF) 2 ] (Ln = Y, Yb, Lu; L = {2,5-(2-C 4 H 3 N)­CPh 2 ) 2 (C 4 H 2 NMe)}) , forming unusual β-diketiminato, imidazolyl, and indolyl moieties . For some of these, a dependence on both the reaction temperature and reaction stoichiometry is found, which shows that both kinetic and thermodynamic products can be accessed under appropriate conditions .…”

“…Zhu and Wang’s team further explored the Lewis acid chemistry of rare earths by demonstrating the insertion of a range of nitrile and isonitrile molecules into metal–alkyl bonds in [RE­(L)­(CH 2 SiMe 3 )­(THF) 2 ] (Ln = Y, Yb, Lu; L = {2,5-(2-C 4 H 3 N)­CPh 2 ) 2 (C 4 H 2 NMe)}) , forming unusual β-diketiminato, imidazolyl, and indolyl moieties . For some of these, a dependence on both the reaction temperature and reaction stoichiometry is found, which shows that both kinetic and thermodynamic products can be accessed under appropriate conditions . Continuing the theme of using rare-earth cations to assemble p-block atoms, Dehnen and co-workers shift our focus from carbon, to the heavy Group 13 and 15 members indium and bismuth .…”