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Coordination complexes of niobium and tantalum pentahalides with a bulky NHC ligand.
- Source :
- Dalton Transactions: An International Journal of Inorganic Chemistry; 4/28/2016, Vol. 45 Issue 16, p6939-6948, 10p
- Publication Year :
- 2016
-
Abstract
- The 1 : 1 molar reactions of niobium and tantalum pentahalides with the monodentate NHC ligand 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (Ipr), in toluene (or benzene) at ca. 80 °C, afforded the complexes NbX<subscript>5</subscript>(Ipr) (X = F, 2; Br, 3) and TaX<subscript>5</subscript>(Ipr) (X = F, 4; Cl, 5; Br, 6), in generally good yields. Complexes 2–6 represent uncommon cases of stable NHC adducts of metal halides with the metal in an oxidation state higher than +4, and also rare examples of Nb–NHC and Ta–NHC bonding systems. In particular, the X-ray molecular structure determined for 6 provides the unprecedented crystallographic characterization of a tantalum compound with a monodentate NHC ligand. DFT results indicate that the metal–carbon bond in 2–6 is a purely σ one. According to NMR studies (<superscript>1</superscript>H, <superscript>13</superscript>C, <superscript>93</superscript>Nb), the formation of 3, 5, 6, as well as the previously communicated NbCl<subscript>5</subscript>(Ipr), 1, proceeded with the intermediacy of [MX<subscript>6</subscript>]<superscript>−</superscript> salts, presumably due to steric reasons. On the other hand, the intermediate formation of MF<subscript>6</subscript><superscript>−</superscript> in the pathways to 2 and 4 was not observed, according to <superscript>19</superscript>F (and <superscript>93</superscript>Nb in the case of 2) NMR. DFT calculations were carried out in order to shed light on structural and mechanistic aspects, and allowed to trace possible reaction routes. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 14779226
- Volume :
- 45
- Issue :
- 16
- Database :
- Complementary Index
- Journal :
- Dalton Transactions: An International Journal of Inorganic Chemistry
- Publication Type :
- Academic Journal
- Accession number :
- 114646406
- Full Text :
- https://doi.org/10.1039/c6dt00533k