3 research outputs found
On the Reaction of Diaminocarbenes with Aroylimines
Several possible
reaction pathways are analyzed for the recently
studied experimental reaction of diaminocarbenes with aroylimines,
where the carbene acted as an oxygen-abstracting agent. A number of
structures corresponding to local minima and transition states are
located by geometry optimization. In contrast to the more recent interpretation
of the mechanism of this process, the reaction does not proceed via
the direct formation of the corresponding carbonyl ylide resulted
from the electrophilic addition of diaminocarbene to the carbonyl
oxygen atom. Two other, more favorable pathways were predicted instead:
the nucleophilic attack of the carbene lone pair on the imino nitrogen
(pathway “a”) or on the carbon atom in the CN
moiety of aroylimine (pathway “b”), in agreement with
predictions of the frontier molecular orbital (FMO) theory. Both intermediate
adducts undergo a subsequent decomposition onto nitrile ylide and
urea. Which of the two pathways becomes preferential depends on the
nature of the substituents: pathway “a” is more favored
for the experimentally studied species, whereas pathway “b”
is thermodynamically preferable for the small-sized model structures
Stable N‑Phosphorylated 1,2,4-Triazol-5-ylidenes: Novel Ligands for Metal Complexes
Synthetic routes to novel N-phosphorylated 1,2,4-triazolium
salts
have been developed. Treatment of the specified salts with strong
base produces new stable N-phosphorylated 1,2,4-triazol-5-ylidenes,
which add Se in two stages (first at the carbene carbon and then at
phosphorus) and rearrange to C-phosphorylated triazoles with heating.
The capacity of such N-phosphorylated triazol-5-ylidenes to act as
bidentate ligands toward transition-metal centers has also been demonstrated;
in particular, the formation of two dinuclear silver carbene complexes
is described herein. The structures of one representative carbene
and of one carbene complex were determined by an X-ray study
Stable N‑Phosphorylated 1,2,4-Triazol-5-ylidenes: Novel Ligands for Metal Complexes
Synthetic routes to novel N-phosphorylated 1,2,4-triazolium
salts
have been developed. Treatment of the specified salts with strong
base produces new stable N-phosphorylated 1,2,4-triazol-5-ylidenes,
which add Se in two stages (first at the carbene carbon and then at
phosphorus) and rearrange to C-phosphorylated triazoles with heating.
The capacity of such N-phosphorylated triazol-5-ylidenes to act as
bidentate ligands toward transition-metal centers has also been demonstrated;
in particular, the formation of two dinuclear silver carbene complexes
is described herein. The structures of one representative carbene
and of one carbene complex were determined by an X-ray study