Physical Organic Chemistry of Transition Metal Carbene Complexes. 4. Kinetics and Equilibria of Methoxide Ion Addition to [Methoxy(phenyl)carbene]pentacarbonylchromium(0) and [Methoxy(phenyl)carbene]pentacarbonyltungsten(0)

Transition metal carbene chemistry 5: Kinetic studies on the nucleophilic substitution reactions of (CO)5MC(SCH3)CH3 (M=Cr and W) with primary amines in aqueous acetonitrile

“…The higher k 1 values (k 1 (W-S)/k 1 (Cr-S) $ 6.2-5.1) are obtained for the reactions of AA, GEE and GA with W-S compared to Cr-S. Similar k 1 (W)/k 1 (Cr) ratios have been reported for the reactions of MeO À in MeOH and various thiolate ions in 50% MeCN-50% H 2 O with M-XR-Z [27,28,35,36,42]. They show a consistent pattern of somewhat enhanced electrophilic reactivity of tungsten complexes.…”

“…The higher reactivity of tungsten carbene complexes over the chromium ones is particularly true for thioalkyl carbene complexes, as is borne out by the results for the reaction of M-SR, 5-M-SR and 6-M-SR with OH À and water [27,28,54]. The higher k 1 values (k 1 (W-S)/k 1 (Cr-S) $ 6.2-5.1) are obtained for the reactions of AA, GEE and GA with W-S compared to Cr-S.…”

“…In non-polar solvents the mechanism was complicated due to hydrogen binding. More recently, a number of rate studies with alcohol [27,28], alkoxide ions [27,28], water [29][30][31][32][33], OH À [29][30][31][32][33], thiols [34][35][36], thiolate ions [34][35][36], amines [33,[37][38][39][40][41][42] and carbanion [43] in polar (mainly water-acetonitrile mixtures) solvent were reported on M-XR and M-XR-Z. Because, in this highly polar solvent there are no hydrogen bonding association as observed in non-polar solvents, which unduly complicate the situation, more clear cut conclusion could be drawn about the mechanistic details.…”

A new versatile binuclear seven-coordinate complex of molybdenum(II), [(μ-Cl)2{Mo(μ-Cl)(SnCl3)(CO)3}2]2−

“…Such formation of alcohol in reaction of a carbene ligand had been observed before [28][29][30][31][32]. In a similar way as with water, the carbene ligand interacts with alcohol [33][34]. Thus, the addition of the H-O bond of norborneol to the carbon atom of molybdanorbornylidene species and the formation of C-O and C-H bonds is one of the method of the formation of (nba) 2 O (Scheme 4).…”

C−C Bond Formation between Fischer Carbene Complexes and Allylic Alcohols by a [3,4] Sigmatropic Rearrangement Promoted by a [1,2] M(CO)5 Shift

“…Species of types I and II are likely involved as active intermediates. Intermediate I, which arises from 1,2-addition of methoxide ion, was characterized for simple carbene complexes by Bernasconi et al, [9] …”