Cationic Bis‐N‐Heterocyclic Carbene (NHC) Ruthenium Complex: Structure and Application as Latent Catalyst in Olefin Metathesis

Abstract

An unexpected cationic bis-N-heterocyclic carbene (NHC) benzylidene ether based ruthenium complex (2 a) was prepared through the double incorporation of an unsymmetrical unsaturated N-heterocyclic carbene (U2 -NHC) ligand that bore an N-substituted cyclododecyl side chain. The isolation and full characterization (including X-ray diffraction studies) of key synthetic intermediates along with theoretical calculations allowed us to understand the mechanism of the overall cationization process. Finally, the newly developed complex 2 a displayed interesting latent behavior during ring-closing metathesis, which could be "switched on" under acidic conditions.

Highly selective macrocyclic ring-closing metathesis of terminal olefins in non-chlorinated solvents at low dilution

“…To tackle this, we focused our attention on Ru-complexes bearing two diaminocarbene units. Indeed, as previously reported by several research groups 25 and more recently by our group, 26 bisNHC arylidene complexes have proved to be highly stable at elevated temperature. Therefore, we decided to replace the PCy 3 ligand by an additional U 2 -NHC unit.…”

“…This lack of reactivity could be explained by the strong binding of the NHC to the metal, which drastically reduces the pre-catalyst initiation rate. 25,26 Recently, Grubbs…”

The chemistry of the carbon-transition metal double and triple bond: Annual survey covering the year 2014

“…When a racemic polymer was subjected to these conditions, a chiral self-sorting leading to the cyclodimer A c c e p t e d M a n u s c r i p t 188 where the binap groups were of like configuration was obtained. The formation of macrocycles through alkyne metathesis depolymerization of alkyne-linked polymers was affected by conformational constraints [1325].…”

Non covalent immobilization of pyrene-tagged ruthenium complexes onto graphene surfaces for recycling in olefin metathesis reactions

“…N-(4-isopropoxy-3-vinylphenyl)-4-(pyren-1-yl)butan-amide 8 (Scheme 2) had to be produced in order to achieve the synthesis of C2 and C3, which have a pyrene tag on the benzylidene-ether ligand. Pyrene-tagged compound 8 was obtained in good yield (74%) by a DCC/DMAP mediated coupling between 4-(pyren-1-yl)butanoic acid and known [22] 4isopropoxy-3-vinylaniline hydrochloride. The Ru complex 7 was converted to M71 ® -type complex C1 by treatment with 2,2,2-trifluoro-N-(4-isopropoxy-3-vinylphenyl)acetamide [23] and CuCl.…”