166903-91-9Relevant academic research and scientific papers
Insertion of isocyanides into tantalum-carbon bonds of azatantalacyclopropane complexes. Crystal structures of TaCp*Cl3(η2-NRCMe2CNHR), TaCp*Me(NR)(NRCMe=CMe2), and TaCp*Me(NR)(η2-NR=CCMe2CMe=NR) (R = 2,6-Me2C6H3)
Galakhov, Mikhail V.,Gómez, Manuel,Jiménez, Gerardo,Royo, Pascual,Pellinghelli, Maria Angela,Tiripicchio, Antonio
, p. 2843 - 2854 (2008/10/09)
Reaction of TaCp*Cl2Me2 with 2 equiv of isocyanides or addition of 1 equiv of isocyanides to azatantalacyclopropane complexes TaCp*Cl2(η2-NRCMe2) (R = 2,6-Me2C6H3, 1a, 2,4,6-Me3C6H2, 1b) at room temperature afforded new imido derivatives TaCp*Cl2(NR) (R = 2,6-Me2C6H3, 2a, 2,4,6-Me3C6H2, 2b) in almost quantitative yields, with simultaneous elimination of the imino ketene, RN=C=CMe2. When the same reactions were carried out in the presence of traces of water, small amounts of cyclic η2-amido-carbene species TaCp*Cl3(η2-NRCMe2-CNHR′) (R = R′ = 2,6-Me2C6H3, 3a, R = 2,6-Me2C6H3, R′ = 2,4,6-Me3C6H2, 3b) were simultaneously obtained. Complexes 3 can also be prepared by heating the corresponding trichloro-isopropylamido complexes TaCp*Cl3(NRiPr), 4, at 90°C in the presence of isocyanide and decompose by further heating at 120°C to give the imido compounds 2. A similar reaction of TaCp*ClnMe4-n (n = 0, 1) with 1 equiv of CN(2,6-Me2C6H3) afforded mono- and dimethylated azatantalacyclopropane derivatives TaCp*ClnMe2-n[η2-N(2,6-Me 2C6H3)CMe2] (n = 1, 5a; n = 0, 5b), which react with one additional equivalent of isocyanide to give imido alkenylamido species TaCp*X[N(2,6-Me2C6H 3)](NR′CMe=CMe2) (X = Cl, R′ = 2,6-Me2C6H3, 6a, and 2,4,6-Me3C6H2, 6b; X = Me, R′ = 2,6-Me2C6H3, 6c, and 2,4,6-Me3C6H2, 6d). Reaction of complexes 6a,c with a third 1 equiv of isocyanide afforded new η2-imino acyl compounds TaCp*X[N(2,6-Me2C6H3)](η 2-NR″=CCMe2CMe=NR′) (X = Cl, R′ = R″ = 2,6-Me2C6H3, 7a; X = Me, R′ = R″ = 2,6-Me2C6H3, 7b, R′ = 2,6-Me2C6H3, R″ = 2,4,6-Me3C6H2, 7c, and R′ = 2,6-Me2C6H3, R″ = tBu, 7d. All compounds were characterized by IR and 1H and 13C NMR measurements, and the activation barrier to rotation around the C=C double bond of the alkenyl group of 6a,c was determined in solution. Molecular structures of 3a, 6c, and 7b were studied by X-ray diffraction methods. Crystals of 3a are monoclinic, space group P21/ n, with Z = 4 in a unit cell of dimensions a = 8.774(4) A?, b = 18.338(8) A?, c = 18.470(7) A?, and β = 91.62(2)°. Crystals of 6c are monoclinic, space group P21/c, with Z = 4 in a unit cell of dimensions a = 8.635(4) A?, b = 34.156(9) A?, c = 10.090(4) A?, and β = 105.94(2)°. Crystals of 7b are orthorhombic, space group P212121, with Z = 4 in a unit cell of dimensions a = 11.622(3) A?, b = 14.141(5) A?, and c = 22.755(9) A?. All three structures were solved from diffractometer data by Patterson and Fourier methods and refined by full-matrix least-squares on the basis of 6620 (3a), 3442 (6c), and 3667 (7b) observed reflections to R and Rw values of 0.0271 and 0.0394 (3a), 0.0272 and 0.0336 (6c), and 0.0450 and 0.0419 (7b), respectively.
