Chemical behaviour of alkyl imido cyclopentadienyl niobium and tantalum(V) complexes in insertion processes. X-ray crystal structures of [MCpCl(NAr){η 2-C(Me)NAr}] (Ar=2,6-Me 2C 6H 3; M=Nb, Cpη 5-C 5H 4SiMe 3; M=Ta, Cp=η 5-C 5Me 5) and [Ta(η 5-C 5Me 5)Me(NAr){η 2-C(CH 2CMe 2Ph)O}] (Ar=2,6-Me 2C 6H 3)

• Published in: Journal of organometallic chemistry 2000, Vol.595 (1), p.36-53
• Main Authors: Castro, Aurora, Galakhov, Mikhail V, Gómez, Manuel, Gómez-Sal, Pilar, Martı́n, Avelino, Sánchez, Fernando
• Format: Article
• Language: English
• Subjects: Imido η 2-iminoacyl, η 2-acyl cyclopentadienyl complexes; Niobium; Tantalum
• ISSN: 0022-328X; 1872-8561
• DOI: 10.1016/S0022-328X(99)00566-5

Pure imido η 2-iminoacyl derivatives [MCpX(NAr){η 2-C(R) NAr}] (Ar=2,6-Me 2C 6H 3; M=Nb, Cp=η 5-C 5H 4SiMe 3=Cp′, X=Cl, R=Me, 1; X=Me, R=NMe 2, 2; Me, 3; X=R=CH 2SiMe 3, 4; CH 2CMe 3, 5; CH 2Ph, 6; M=Ta, Cp=η 5-C 5Me 5=Cp*, X=Cl, R=Me, 7; CH 2SiMe 3, 8; CH 2CMe 2Ph, 9; CH 2CMe 3, 10; CH 2C 6H 5, 11; 2-(CH 2NMe 2)C 6H 4, 12; NMe 2, 13; X=R=CH 2SiMe 3, 14; CH 2CMe 2Ph, 15; CH 2CMe 3, 16; CH 2C 6H 5, 17; C 6H 5, 18) can be prepared by reaction of chloro alkyl or dialkyl imido complexes MCpXR(NAr) with 1 equivalent of 2,6-Me 2C 6H 3NC. Reaction of alkyl methyl imido complexes TaCp*RMe(NAr) with 1 equivalent of isocyanide 2,6-Me 2C 6H 3NC takes place with migration of alkyl or methyl group, leading to the formation of a mixture of methyl η 2-alkyliminoacyl [TaCp*Me(NAr){η 2-C(R) NAr}] (Ar=2,6-Me 2C 6H 3; R=CH 2SiMe 3, 19; CH 2Ph, 21; CH 2CMe 2Ph, 23; CH 2CMe 3, 25; C 6H 5, 27; 2-(CH 2NMe 2)C 6H 4, 29; NMe 2, 30) and alkyl η 2-methyliminoacyl [TaCp*R(NAr){η 2-C(Me) NAr}] (Ar=2,6-Me 2C 6H 3; R=CH 2SiMe 3, 20; CH 2Ph, 22; CH 2CMe 2Ph, 24; CH 2CMe 3, 26; C 6H 5, 28) complexes. Alkyl imido derivatives also react with CO to give alkyl η 2-acyl [TaCp*X(NAr){η 2-C(R) O}] (Ar=2,6-Me 2C 6H 3; X=R=CH 2SiMe 3, 31; CH 2CMe 2Ph, 32; CH 2CMe 3, 33; CH 2Ph, 34), chloro η 2-acyl (X=Cl, R=CH 2CMe 2Ph, 35; NMe 2, 36) and methyl η 2-acyl (X=Me, R=CH 2CMe 2Ph, 37; CH 2CMe 3, 38) complexes. Dinuclear ene diolate complexes [{TaCp*X(NAr)} 2{μ-η 2-OC(R) C(R)O}] (Ar=2,6-Me 2C 6H 3; X=Cl, R=CH 2CMe 3, 39; X=Me, R=2-(CH 2NMe 2)C 6H 4, 40) are formed by reaction of the chloro and methyl alkyl imido derivatives with carbon monoxide, whereas using [TaCp*XR(NAr)] (Ar=2,6-Me 2C 6H 3; X=Cl, R=CH 2CMe 3; X=R=Ph) a different sequence of reactions takes place leading finally to oxo η 2-iminoacyl complexes [TaCp*X(O){η 2-C(R) NAr}] (X=Cl, R=CH 2CMe 3, 41; X=R=Ph, 42). All compounds were characterised by NMR ( 1H, 13C) spectroscopy and IR measurements. The molecular structures of 1, 7 and 37 were studied by X-ray diffraction methods and are discussed.