Alkynylcarbyne complexes containing various tri- and bidentate ligands such as cyclopentadienide, tris(pyrazolyl)borate, bis(pyrazolyl)acetate and tmeda: synthesis and spectroscopic properties (original) (raw)

2002, Journal of Organometallic Chemistry

The (alkynylcarbyne)tungsten complexes [L 3 (CO) 2 W C C C R] (3a,b-6a,b) [L 3 = hydro[tris(3,5-dimethylpyrazol-1-yl)]borato (Tp%, 3), hydro[tris(pyrazol-1-yl)]borato (Tp, 4), cyclopentadienyl (Cp, 5), bis(3,5-dimethylpyrazol-1-yl)acetato (bdmpza, 6); R =SiMe 3 (a), Ph (b)] were prepared in a stepwise fashion from [W(CO) 6 ] and Li[C CR], (CF 3 CO) 2 O and M[L 3 ] (M=Na, K). The formation of 6a,b was highly selective, only complexes with a trans arrangement of the carboxylate group of bdmpza and the alkynylcarbyne ligand were detected. The reaction of [W(CO) 6 ] with Li[C CR], C 2 O 2 Cl 2 and tmeda afforded trans-[Cl(CO) 2 (tmeda)W C C C R] (7a,b). The electron-donating potential of the different tripodal ligands L 3 was studied by IR-and 13 C-NMR spectroscopy and compared to that of the ligand combination Cl/tmeda. The IR data suggest that in these complexes bdmpza is a weaker electron donor than Tp% and Tp but displays stronger electron-donating abilities than Cp. The structures of 6b and 7b were established by X-ray structural analyses.