Search

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 NbX5(Ipr) (X = F, 2; Br, 3) and TaX5(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 (1H, 13C, 93Nb), the formation of 3, 5, 6, as well as the previously communicated NbCl5(Ipr), 1, proceeded with the intermediacy of [MX6]− salts, presumably due to steric reasons. On the other hand, the intermediate formation of MF6− in the pathways to 2 and 4 was not observed, according to 19F (and 93Nb 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]

Several mono- or bis-alkynyl derivatives of general formula Pt6(μ-PBut2)4(CO)4X(C≡C–R), Pt6(μ-PBut2)4(CO)4(C≡C–R)2 or Pt6(μ-PBut2)4(CO)4(C≡C–R)(C≡C–R′) were obtained under Sonogashira type conditions. The new clusters have been characterized with microanalysis and using IR and multinuclear NMR spectroscopy. The crystal and molecular structures of Pt6(μ-PBut2)4(CO)4(C≡C–R)2 (R = H, C6H4-4-n-C5H11) are presented and electrochemical and spectroelectrochemical studies of some representative compounds are also reported. [ABSTRACT FROM AUTHOR]

The metal halides of Group 5 MX5 (M = Nb, Ta; X = F, Cl, Br) react with ketones and acetylacetones affording the octahedral complexes [MX5(ketone)] (2a-j) and [TaX4{κ2(O)-OC(Me)C(R)C(Me)O}] (R = H, Me, 5a-e), respectively. The adducts [MX5(acetone)] are still reactive towards acetone, acetophenone or benzophenone, giving the aldolate species [MX4{κ2(O)-OC(Me)CH2C(R)(R′)O}] (3a-e). The syntheses of 3b (M = Ta, X = F, R = R′ = Ph) and 3d (M = Ta, X = Cl, R = Me, R′ = Ph) take place with concomitant formation of [(Ph2CO)2-H][TaF6], 4a, and [(MePhCO)2-H][TaCl6], 4b, respectively. The compounds [acacH2][TaF6], 6, and [TaF{OC(Me)C(Me)C(Me)O}3][TaF6], 7, have been isolated as by-products in the reactions of TaF5 with acacH and 3-methyl-2,4-pentanedione, respectively. The molecular structures of 2i, 3c, 4a, 4b and 7 have been ascertained by single crystal X-ray diffraction studies. [ABSTRACT FROM AUTHOR]

Correction for ‘Self-assembly of arene ruthenium acylpyrazolone fragments to tetranuclear metallacycles. Molecular structures and solid-state 15N CPMAS NMR correlations’ by Riccardo Pettinari et al., Dalton Trans., 2016, 45, 3974–3982. [ABSTRACT FROM AUTHOR]

Several mono- or bis-alkynyl derivatives of general formula Pt6(μ-PBut2)4(CO)4X(C≡C–R), Pt6(μ-PBut2)4(CO)4(C≡C–R)2 or Pt6(μ-PBut2)4(CO)4(C≡C–R)(C≡C–R′) were obtained under Sonogashira type conditions. The new clusters have been characterized with microanalysis and using IR and multinuclear NMR spectroscopy. The crystal and molecular structures of Pt6(μ-PBut2)4(CO)4(C≡C–R)2 (R = H, C6H4-4-n-C5H11) are presented and electrochemical and spectroelectrochemical studies of some representative compounds are also reported. [ABSTRACT FROM AUTHOR]