Hydroboration of Alkynes with Zwitterionic Ruthenium–Borate Complexes: Novel Vinylborane Complexes. Issue 32 (26th June 2015)

• Record Type: Journal Article
• Authors: Anju, R. S.; Mondal, Bijan; Saha, Koushik; Panja, Subir; Varghese, Babu; Ghosh, Sundargopal
• Is Part Of: Chemistry. Volume 21:Issue 32(2015)
• Page Start: 11393
• Page End: 11400
• Publication Date: 2015-06-26
• Subjects: Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201501107
• Languages: English
• ISSNs: 0947-6539

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>Building upon previous studies on the synthesis of bis(sigma)borate and agostic complexes of ruthenium, the chemistry of <italic>nido</italic>‐[(Cp*Ru)<sub>2</sub>B<sub>3</sub>H<sub>9</sub>] (<bold>1</bold>) with other ligand systems was explored. In this regard, mild thermolysis of <italic>nido</italic>‐<bold>1</bold> with 2‐mercaptobenzothiazole (2‐mbzt), 2‐mercaptobenzoxazole (2‐mbzo) and 2‐mercaptobenzimidazole (2‐mbzi) ligands were performed which led to the isolation of bis(sigma)borate complexes [Cp*RuBH<sub>3</sub>L] (<bold>2 a</bold>–<bold>c</bold>) and β‐agostic complexes [Cp*RuBH<sub>2</sub>L<sub>2</sub>] (<bold>3 a</bold>–<bold>c</bold>; <bold>2 a</bold>, <bold>3 a</bold>: L=C<sub>7</sub>H<sub>4</sub>NS<sub>2</sub>; <bold>2 b</bold>, <bold>3 b</bold>: L=C<sub>7</sub>H<sub>4</sub>NSO; <bold>2 c</bold>, <bold>3 c</bold>: L=C<sub>7</sub>H<sub>5</sub>N<sub>2</sub>S). Further, the chemistry of these novel complexes towards various diphosphine ligands was investigated. Room temperature treatment of <bold>3 a</bold> with [PPh<sub>2</sub>(CH<sub>2</sub>)<sub><italic>n</italic></sub>PPh<sub>2</sub>] (<italic>n</italic>=1–3) yielded [Cp*Ru(PPh<sub>2</sub>(CH<sub>2</sub>)<sub><italic>n</italic></sub>PPh<sub>2</sub>)‐BH<sub>2</sub>(L<sub>2</sub>)] (<bold>4 a</bold>–<bold>c</bold>; <bold>4 a</bold>: <italic>n</italic>=1; <bold>4 b</bold>: <italic>n</italic>=2; <bold>4 c</bold>: <italic>n</italic>=3; L=C<sub>7</sub>H<sub>4</sub>NS<sub>2</sub>). Mild thermolysis of <bold>2 a</bold> with [PPh<sub>2</sub>(CH<sub>2</sub>)<sub><italic>n</italic></sub>PPh<sub>2</sub>] (<italic>n</italic>=1–3) led to the isolation of [Cp*Ru(PPh<sub>2</sub>(CH<sub>2</sub>)<sub><italic>n</italic></sub>PPh<sub>2</sub>)(L)] (L=C<sub>7</sub>H<sub>4</sub>NS<sub>2</sub><bold>5 a</bold>–<bold>c</bold>; <bold>5 a</bold>: <italic>n</italic>=1; <bold>5 b</bold>: <italic>n</italic>=2; <bold>5 c</bold>: <italic>n</italic>=3). Treatment of <bold>4 a</bold> with terminal alkynes causes a hydroboration reaction to generate vinylborane complexes [Cp*Ru(RCCH<sub>2</sub>)BH(L<sub>2</sub>)] (<bold>6</bold> and <bold>7</bold>; <bold>6</bold>: R=Ph; <bold>7</bold>: R=COOCH<sub>3</sub>; L=C<sub>7</sub>H<sub>4</sub>NS<sub>2</sub>). Complexes <bold>6</bold> and <bold>7</bold> can also be viewed as η‐alkene complexes of ruthenium that feature a dative bond to the ruthenium centre from the vinylinic double bond. In addition, DFT computations were performed to shed light on the bonding and electronic structures of the new compounds.</p> </abstract>