671215-34-2Relevant academic research and scientific papers
Pentamethylcyclopentadienyl tantalum(V) complexes (Cp*Ta) containing 1,2,3-triazolato ligands
Herberhold, Max,Goller, Achim,Milius, Wolfgang
, p. 1162 - 1168 (2003)
Starting from Cp*TaCl4 (1), the azido complexes {Cp* TaCl(N3)2(μ-N3)}2 (2) and Cp*Ta(N3)Ph3 (3) were prepared which react with dimethyl acetylene dicarboxylate, MeOOC-C≡C-COOMe (a), in a [2+3] cycloaddition to give the mononuclear 1,2,3-triazolato complexes Cp*TaCl(N3)2[N2N(Me)C(COOMe)C-(COO)] (5) and Cp*TaPh3[N3C2(COOMe)2] (6). Complex 5 contains an N(3)-methylated 1,2,3-triazolato chelate ligand which is bound to tantalum(V) through N(1) and a 5-carboxylato substituent, whereas the 1,2,3-triazolato ligand in 6 is coordinated only through N(2). The monodentate-symmetrical coordination of the 1,2,3-triazolato-heterocycle (as in 6) is also realized, if one chloro ligand per Cp*Ta in 2 or in {Cp*TaCl2(μ-OH)}2(μ-O) (4) reacts with 1-trimethylsilyl-4,5-di(methoxycarbonyl)-1,2,3-triazole (b) under formation of Me3SiCl; the products (7 and 8, respectively) remain dinuclear. On the contrary, the reaction of Cp*TaCl4 (1) with 1-silylated 1,2,3-triazoles led to the mononuclear complex of the heterocyclic chelate ligand, Cp*TaCl3-[N2N(R)C(COOR)C(COO)] (R = Me (9), Et (10)). Both types of 1,2,3-triazolato ligands are present in the complex Cp*TaCl2[N3C2(COOMe)2][N 2N(Me)-C(COOMe)C(COO)] (11) which was obtained by the reaction of 9 with 4,5-di(methoxycarbonyl)-1,2,3-triazole (e) in the presence of NEt 3. The structures of the new complexes were deduced on the basis of their IR, 1H and 13C NMR spectra; the X-ray structure analysis of 9 confirmed the formation of a 5-carboxylato-1,2,3-triazolato chelate ligand by migration of an ester methyl group to N(3).
