Reactive N‐Protonated Isocyanate Species Stabilized by Bis(μ‐hydroxo)divanadium(IV)‐Substituted Polyoxometalate

Preparation of tetrabutylammonium salt of a mono-Ru(iii)-substituted α-Keggin-type silicotungstate with a 4,4′-bipyridine ligand and its electrochemical behaviour in organic solvents

“…The 1 H-NMR spectrum showed peak broadening due to the paramagnetic effect of Ru III . Since a similar peak broadening was observed for the TBA cation in TBA 4 [γ-SiV IV 2 W 10 O 36 (μ-OH) 4 ] (3.16, 1.64, 1.40 and 0.98 ppm in CD 3 CN), 38 the four large 1 H-NMR signals at 3.33, 1.78, 1.51 and 1.05 ppm were assignable to the TBA cation in 1. It was considered that the two small signals at 6.93 and 6.27 ppm were assignable to two protons (H (7) and H( 8)) in the bipyridine ligand.…”

Ketenes and Other Cumulenes as Reactive Intermediates

“…245 Reaction of the polyoxometalate (TBA) 4 [γ-Si-(V IV 2 ) 2 W 10 O 36 (μ−OH)] 4 with phenylisocyanate in acetone and 1,2-chloroethane gives (TBA) 2 [γ-SiV IV 2 W 10 O 38 (μ-OH) 2 -(PhNHCO) 2 ] with the X-ray structure 309 (Figure 11) in 71% yield. 246 This N-protonated divanadium(IV) isocyanate species is stabilized by the polyoxometalate anionic cluster, and catalyzes the cyclotrimerization of phenylisocyanate.…”

“…Adduct from polyoxometalate reaction with phenylisocyanate. Reproduced with permission from ref . Copyright 2012 Wiley VCH.…”

Catalysts for Isocyanate Cyclotrimerization

“…Generally accepted Lewis acidic cyclotrimerization mechanism. Tungsten-vanadium complex 119 Aryl ACN [119] Rare earth metal amides 120 Aryl, alkyl THF [86] Rare earth metal amides 121 Aryl, alkyl THF [86] Rare earth metal amides 122 Aryl, alkyl THF, toluene, DCM [120] plored as selective cyclotrimerization catalysts. A Ge based catalyst had a better catalytic performance in bulk cyclotrimerization of phenyl isocyanates at room temperature and 98 % yield was achieved within 16 min, while only 94 % conversion was reached after 210 min with the Sn based catalyst.…”