Carbodiimide metathesis catalyzed by vanadium oxo and imido complexes via imido transfer

Birdwhistell, K. R.; Lanza, Joann; Pasos, J.

doi:10.1016/s0022-328x(99)00142-4

Cited by 59 publications

(63 citation statements)

References 27 publications

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“…The inactivity of the former can be attributed to the low solubility of the vanadium compound in the reaction media. The moderate activity of VO(acac) 2 was not unexpected considering this complex was an efficient catalyst for carbodiimide metathesis [7].…”

Section: Resultsmentioning

confidence: 82%

“…Particularly, compounds of the formula V(NAr)X 3 (X ¼ Cl, OR) have been successfully employed in this reaction [7]. The proposed catalytic cycle for the process implies the formation of a diazametallacyclobutane intermediate derived from the [2 + 2] cycloaddition between the metal-nitrogen double bond and the double bond of the unsaturated carbodiimide (Scheme 2).…”

Section: Introductionmentioning

confidence: 99%

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Guanylation of aromatic amines catalyzed by vanadium imido complexes

Montilla

Pastor

Galindo

2004

Journal of Organometallic Chemistry

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Section: Resultsmentioning

confidence: 82%

Section: Introductionmentioning

confidence: 99%

Guanylation of aromatic amines catalyzed by vanadium imido complexes

Montilla

Pastor

Galindo

2004

Journal of Organometallic Chemistry

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“…33 The V=NR moiety would then promote the metathesis with a second carbodiimide R¢N=C=NR¢ to afford RN=C=NR¢ and the V=NR¢ moiety (Scheme 2). 33 The V=NR moiety would then promote the metathesis with a second carbodiimide R¢N=C=NR¢ to afford RN=C=NR¢ and the V=NR¢ moiety (Scheme 2).…”

Section: Nbocl 3 + Cyn=c=ncy → Nb-species + Cyn=c=omentioning

confidence: 99%

The solid state structure and reactivity of NbCl5·(N,N′-dicyclohexylurea) in solution: evidence for co-ordinated urea dehydration to the relevant carbodiimide

et al. 2010

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NbCl(5) x (N,N'-dicyclohexylurea) 1a owns a distorted octahedral structure due to intramolecular NH...Cl bonding. The unit cell contains four units which are intermolecularly NH...Cl and NH...N bonded. An extended intramolecular network of H-bonding (N-H...Cl, CH...Cl, CH...N) causes the 3D self assembling of the units. Upon addition of base, the HCl release from 1a is observed with the transfer to Nb of the O-atom of the carbonylic function of the starting urea which is converted into the relevant carbodiimide CyN=C=NCy 4. The latter is quantitatively released by adding an excess of NEt(3) at 308 K (py and DBU are less efficient) with formation of the known NbOCl(3)(NEt(3))(2), isolated in quantitative yield. Increasing the temperature leads to a loss in selectivity as the formed DCC undergoes further reactions. At 350 K, the isocyanate CyN=C=O has been isolated in 60% yield besides a mixture of Nb-complexes. DFT calculations have been coupled to IR and NMR experiments for characterizing possible reaction intermediates and the behaviour of 1a. Several other MCl(x) species (ScCl(3), YCl(3), LaCl(3), TiCl(4), TaCl(5), AlCl(3), SnCl(4)) have been shown to be able to co-ordinate DCU but not all of them promote the conversion of urea into DCC.

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“…Early reports involving W based catalysts suggest that imido transfer occurs via a diazametallacyclobutane intermediate that arises from a [2+2] cycloaddition between the metal-nitrogen and carbonnitrogen double bonds [107][108]. Building on these reports, Birdwhistell and co-workers have developed a variety of vanadium oxo and imido complexes that catalyzed the metathesis of carbodiimides ( Table 3) [109]. These complexes also mediate the condensation of aryl isocyanates to N,N'-diarylcarbodiimides ( Table 2) [110].…”

Section: B Metathesis Reactionsmentioning

confidence: 99%