Synthesis, Structural Characterisation and Reactivity of New Dinuclear Monocyclopentadienyl Imidoniobium and ‐tantalum Complexes − X‐ray Crystal Structures of [{Nb(η 5 ‐C 5 H 4 SiMe 3 )Cl 2 } 2 (μ‐1,4‐NC 6 H 4 N)], [{Ta(η 5 ‐C 5 Me 5 )Cl 2 } 2 (μ‐1,4‐NC 6 H 4 N)] and [{Ta(η 5 ‐C 5 Me 5 )(CH 2 SiMe 3 ) 2 } 2 (μ‐1,4‐NC 6 H 4 N)]
The preparation of a family of dinuclear monocyclopentadienyl imidoniobium and -tantalum complexes was achieved by two different synthetic routes. The diimido complexes [{M(Cp′)Cl2}2(μ-1,i-NC6H4N)] [Cp′ = η5-C5H4SiMe3, M = Nb, i = 4 (1); Cp′ = η5-C5H4SiMe3, M = Nb, i = 3 (2); Cp′ = η5-C5H4SiMe3, M = Nb, i = 2 (3); Cp′ = η5-C5Me5, M = Nb, i = 4 (4); Cp′ = η5-C5Me5, M = Nb, i = 3 (5); Cp′ = η5-C5H4SiMe3, M = Ta, i = 4 (6); Cp′ = η5-C5H4SiMe3, M = Ta, i = 3 (7)] were prepared by the reaction of one equivalent of the trichloro precursor [{MCl3}2(μ-1,i-NC6H4N)] (M = Nb, Ta, i = 4, 3 or 2) with two equivalents of either C5H4(SiMe3)2 or C5Me5(SiMe3). Complexes 1−7 can also be prepared by the react…
Electrochemical and chemical reduction of niobocene dichlorides in the presence of carbon dioxide
Abstract The chemical and electrochemical reduction of the niobocene dichlorides [Nb(η5-C5H4SiMe3)2Cl2]1, [Nb(η5-C5Me5)2Cl2] 2 and [Nb(η5-C5Me4Et)2Cl2] 3, in the presence of carbon dioxide has been investigated. Formation of compounds of the type [Cp2Nb(CO2)] and [Cp2(∗)NbCl(CO2))] 1 has been established by means of IR, ESR and/or NMR spectroscopy. They contain a labile η2-CO2. The order of stability increases with the degree of substitution the Cp. Less stable intermediates in the reduction of the system [Cp2NbCl2]/CO2 are discussed on the basis of cyclovoltammetric and coulometric data.
Synthesis and characterization of new allyl palladium complexes with thionate ligands; X-ray molecular structures of [Pd3(η3-C4H7)3{pm(Me)2S}2](CF3SO3) and [Pd{pm(Me)2S}2], η3-C4H7=η3-2-MeC3H4, pm(Me)2S=Pyridine-4,6-dimethyl-2-thionate
Abstract The reaction of [Pd(η3-C4H7)]CF3SO3 (η3-C4H7=η3-2-MeC3H4) (1), prepared in situ by reaction of [Pd(η3-C4H7)Cl]2 with AgCF3SO3, with various thionate ligands, gives new polymeric complexes formulated as [Pd(η3-C4H7)(RS)]n (2) [RS=pyS (pyridine-2-thionate)], im(Me)S(imidazole-3-methyl-2-thionate) (3), pm(Me)2S (pyrimidine-4,6-dimethyl-2-thionate) (4). A solution of 4 contaminated with KCF3SO3 evolves to give crystals that correspond to a new polymeric species whose X-ray crystal molecular structure indicates the presence of cationic infinite chains built of trinuclear units, [Pd3(η3-C4H7)3{pm(Me)2S}2]+ (5). Finally, the formation of a mononuclear thionate-containing palladium complex…
Synthesis and reactivity of new mono- and dinuclear niobium and tantalum imido complexes: X-ray crystal structure of [Ta(η5-C5H4SiMe3)Cl2{NC6Me4-4-(N(SiMe3)2)}]
Abstract The reaction of [1,4-{SiMe3(H)N}2C6Me4] (1) with 2 equivalents of LiBun followed by the addition of SiMe3Cl gave the diamine compound [1,4-{(SiMe3)2N}2C6Me4] (2). [Ta(η5-C5H4SiMe3)Cl4] reacts with 2, in a 2:1 stoichiometric ratio, to initially yield a mixture of the dinuclear, [{Ta(η5-C5H4SiMe3)Cl2}2(μ-1,4-NC6Me4N)] (3), and mononuclear, [Ta(η5-C5H4SiMe3)Cl2{ NC6Me4-4-(N(SiMe3)2)}] (4), imido complexes. 3 can be obtained exclusively by submitting the reaction mixture to repeated cycles of evacuation, to remove volatiles, followed by addition of solvent and subsequent heating. The mononuclear imido complex 4 was isolated from the reaction of [Ta(η5-C5H4SiMe3)Cl4] with 2 in a 1:1 sto…