Trapping Unstable Terminal M−O Multiple Bonds of Monocyclopentadienyl Niobium and Tantalum Complexes with Lewis Acids

Abstract

Hydrolysis of [NbCp'Cl(4)] (Cp' = η(5)-C(5)H(4)SiMe(3)) with the water adduct H(2)O·B(C(6)F(5))(3) afforded the oxo-borane compound [NbCp'Cl(2){O·B(C(6)F(5))(3)}] (2a). This compound reacted with [MgBz(2)(THF)(2)] giving [NbCp'Bz(2){O·B(C(6)F(5))(3)}] (2b), whereas [NbCp'Me(2){O·B(C(6)F(5))(3)}] (2c) was obtained from the reaction of [NbCp'Me(4)] with H(2)O·B(C(6)F(5))(3). Addition of Al(C(6)F(5))(3) to solutions containing the oxo-borane compounds [MCp(R)X(2){O·B(C(6)F(5))(3)}] (M = Ta, Cp(R) = η(5)-C(5)Me(5) (Cp*), X = Cl 1a, Bz 1b, Me 1c; M = Nb, Cp(R) = Cp', X = Cl 2a) afforded the oxo-alane complexes [MCp(R)X(2){O·Al(C(6)F(5))(3)}] (M = Ta, Cp(R) = Cp*, X = Cl 3a, Bz 3b, Me 3c; M = Nb, Cp(R) = Cp', X = Cl 4a), releasing B(C(6)F(5))(3). Compound 3a was also obtained by addition of Al(C(6)F(5))(3) to the dinuclear μ-oxo compound [TaCp*Cl(2)(μ-O)](2), meanwhile addition of the water adduct H(2)O·Al(C(6)F(5))(3) to [TaCp*Me(4)] gave complex 3c. The structure of 2a and 3a was obtained by X-ray diffraction studies. Density functional theory (DFT) calculations were carried out to further understand these types of oxo compounds.

Oxygenextrusion from amidate ligands to generate terminal TaO units under reducing conditions. How to successfully use amidate ligands in dinitrogen coordination chemistry

“…Thus, this approach starting from discrete amidate complexes, is consistent with previous literature suggestions. 24,37 With the observation that amidate ligands are transformed under the reducing conditions normally required for the formation of N 2 complexes, a fundamental question regarding the suitability of amidates as a supporting auxiliary ligand arises. To address this concern, other milder synthetic routes into amidate ligated N 2 complexes were pursued.…”

High Preventive Effect of G2-S16 Anionic Carbosilane Dendrimer against Sexually Transmitted HSV-2 Infection

“…Even though every year thousands of nanocompounds and dendrimers are published, only the G2-S16 dendrimer will be described in this work [14]. The stable and water-soluble G2-S16 anionic carbosilane dendrimer ( Figure 2) was synthesized according to the methods reported by the Dendrimers for Biomedical Applications research group (BioInDen) of the University of Alcala (Madrid, Spain) [21,23,82]. The G2-S16 dendrimer is a second-generation dendrimer presenting 16 sulfonate groups in its periphery.…”

Boron, aluminium, gallium, indium and thallium

“…The related Al(C 6 F 5 ) 3 adducts have also been reported. 141 Treatment of 1,6-diamino-1,6-diphenyl-1,3,5-hexatriene with 2 molar equivalents of HB(C 6 F 5 ) 2 results in tautomerisation of the stable primary enamine to its bis(imine) tautomer, which is stabilised by twofold imine-borane Lewis base-Lewis acid adduct formation. 134 The reaction of (C 6 F 5 ) 2 B(OEt) with t Bu 2 P(CH 2 Li) yields the cyclic phosphonium ethoxyborate (C 6 F 5 )(OEt)B(CH 2 )(C 6 F 4 )P t Bu 2 , via B-C adduct formation and ortho-fluoride substitution, and has been structurally characterised by X-ray diffraction.…”