Synthetic Diversity in the Formation of Triazoles from Nitriles and Diazo Compounds Using Metallocenes of Electropositive Metals

Reactions of [(C 5 Me 5 ) 2 Ln][(μ - Ph) 2 BPh 2 ] complexes with Li[Me 3 SiCN 2 ] form dimeric isocyanotrimethylsilyl amide complexes {(C 5 Me 5 ) 2 Ln[μ-N(SiMe 3 )NC]} 2, not only for Ln = Sm ( 1-Sm ) and La ( 1-La ) but also for the intermediate and small size metal ions Ln = Nd, Y, Yb, and Lu. Complexes 1-Y and 1-Yb were characterized by X-ray crystallography and are structurally similar to 1-Sm and 1-La . A more convenient synthesis of 1-Sm and 1-La from the corresponding (C 5 Me 5 ) 2 LnCl 2 K(THF) 2 “ate” salts with Li[Me 3 SiCN 2 ] is also reported. Analogues of reactions of 1-Sm and 1-La with Me 3 CCN that form the 1,2,3-triazolato complexes (C 5 Me 5 ) 2 Ln(NCCMe 3 )[ NNC(SiMe 3 )C(CMe 3 ) N] ( 2-Sm, 2-La ) were examined with C 6 H 5 CH 2 CN and Me 3 SiCN to investigate the diversity of the triazoles accessible by this route. Complex 1-La reacts with C 6 H 5 CH 2 CN to make a 1,2,3-triazole complex, but in contrast to 2-La, the product is a base-free dimer in which each triazole is ligated by two metallocenes, {(C 5 Me 5 ) 2 La[μ-η 1:η 2 - NNC(SiMe 3 )C(CH 2 C 6 H 5 ) N]} 2, 3 . The reaction of 1-La with Me 3 SiCN involves Si−C bond cleavage, and a nitrile-solvated cyanide trimer, [(C 5 Me 5 ) 2 La(μ-CN)(NCSiMe 3 )] 3, 4, was isolated. The reaction of 1-La with the isocyanide reagent Me 3 SiCH 2 NC also generated a cyanide trimer, this time via N−C bond cleavage as an isocyanide solvate, [(C 5 Me 5 ) 2 La(μ-CN)(Me 3 SiCH 2 NC)] 3, 5 . Unsubstituted 1,2,3-triazoles {(C 5 Me 5 ) 2 Ln[μ-η 1:η 2 - NNC(SiMe 3 )C(H) N]} 2 ( 6-Sm, 6-La) can be isolated directly from 1-Sm and 1-La in reactions that involve N−N bond cleavage.