Neutral and Cationic Molybdenum Imido Alkylidene N‐Heterocyclic Carbene Complexes: Reactivity in Selected Olefin Metathesis Reactions and Immobilization on Silica. Issue 39 (6th August 2015)

• Record Type: Journal Article
• Authors: Sen, Suman; Schowner, Roman; Imbrich, Dominik A.; Frey, Wolfgang; Hunger, Michael; Buchmeiser, Michael R.
• Is Part Of: Chemistry. Volume 21:Issue 39(2015)
• Page Start: 13778
• Page End: 13787
• Publication Date: 2015-08-06
• Subjects: Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201501615
• Languages: English
• ISSNs: 0947-6539

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>The synthesis and single‐crystal X‐ray structures of the novel molybdenum imido alkylidene N‐heterocyclic carbene complexes [Mo(N‐2, 6‐Me<sub>2</sub>C<sub>6</sub>H<sub>3</sub>)(IMesH<sub>2</sub>)(CHCMe<sub>2</sub>Ph)(OTf)<sub>2</sub>] (<bold>3</bold>), [Mo(N‐2, 6‐Me<sub>2</sub>C<sub>6</sub>H<sub>3</sub>)(IMes)(CHCMe<sub>2</sub>Ph)(OTf)<sub>2</sub>] (<bold>4</bold>), [Mo(N‐2, 6‐Me<sub>2</sub>C<sub>6</sub>H<sub>3</sub>)(IMesH<sub>2</sub>)(CHCMe<sub>2</sub>Ph)(OTf){OCH(CF<sub>3</sub>)<sub>2</sub>}] (<bold>5</bold>), [Mo(N‐2, 6‐Me<sub>2</sub>C<sub>6</sub>H<sub>3</sub>)(CH<sub>3</sub>CN)(IMesH<sub>2</sub>)(CHCMe<sub>2</sub>Ph)(OTf)]<sup>+</sup> BAr<sub>F</sub><sup>−</sup> (<bold>6</bold>), [Mo(N‐2, 6‐Cl<sub>2</sub>C<sub>6</sub>H<sub>3</sub>)(IMesH<sub>2</sub>)(CHCMe<sub>3</sub>)(OTf)<sub>2</sub>] (<bold>7</bold>) and [Mo(N‐2, 6‐Cl<sub>2</sub>C<sub>6</sub>H<sub>3</sub>)(IMes)(CHCMe<sub>3</sub>)(OTf)<sub>2</sub>] (<bold>8</bold>) are reported (IMesH<sub>2</sub>=1, 3‐dimesitylimidazolidin‐2‐ylidene, IMes=1, 3‐dimesitylimidazolin‐2‐ylidene, BAr<sub>F</sub><sup>−</sup>=tetrakis‐[3, 5‐bis(trifluoromethyl)phenyl] borate, OTf=CF<sub>3</sub>SO<sub>3</sub><sup>−</sup>). Also, silica‐immobilized versions <bold>I1</bold> and <bold>I2</bold> were prepared. Catalysts <bold>3</bold>–<bold>8</bold>, <bold>I1</bold> and <bold>I2</bold> were used in homo‐, cross‐, and ring‐closing metathesis (RCM) reactions and in the cyclopolymerization of α, ω‐diynes. In the RCM of α, ω‐dienes, in the homometathesis of 1‐alkenes, and in the ethenolysis of cyclooctene, turnover numbers (TONs) up to 100 000, 210 000 and 30 000, respectively, were achieved. With <bold>I1</bold> and <bold>I2</bold>, virtually Mo‐free products were obtained (<3 ppm Mo). With 1, 6‐hepta‐ and 1, 7‐octadiynes, catalysts <bold>3</bold>, <bold>4</bold>, and <bold>5</bold> allowed for the regioselective cyclopolymerization of 4, 4‐bis(ethoxycarbonyl)‐1, 6‐heptadiyne, 4, 4‐bis(hydroxymethyl)‐1, 6‐heptadiyne, 4, 4‐bis[(3, 5‐diethoxybenzoyloxy)methyl]‐1, 6‐heptadiyne, 4, 4, 5, 5‐tetrakis(ethoxycarbonyl)‐1, 7‐octadiyne, and 1, 6‐heptadiyne‐4‐carboxylic acid, underlining the high functional‐group tolerance of these novel Group 6 metal alkylidenes.</p> </abstract>