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Updated: Apr 8, 2026
The Synthesis, Characterization and Reactivity of a Series of Ruthenium N-triphosPh Complexes
Published on: April 10, 2015
Hydroboration of Alkynes with Zwitterionic Ruthenium-Borate Complexes: Novel Vinylborane Complexes
R S Anju1, Bijan Mondal1, Koushik Saha1
1Department of Chemistry, Indian Institute of Technology Madras, Chennai 600036 (India).
Abstract:
Building upon previous studies on the synthesis of bis(sigma)borate and agostic complexes of ruthenium, the chemistry of nido-[(Cp*Ru)2 B3 H9] (1) with other ligand systems was explored. In this regard, mild thermolysis of nido-1 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*RuBH3 L] (2 a-c) and β-agostic complexes [Cp*RuBH2 L2] (3 a-c; 2 a, 3 a: L=C7 H4 NS2 ; 2 b, 3 b: L=C7 H4 NSO; 2 c, 3 c: L=C7 H5 N2 S). Further, the chemistry of these novel complexes towards various diphosphine ligands was investigated. Room temperature treatment of 3 a with [PPh2 (CH2 )n PPh2 ] (n=1-3) yielded [Cp*Ru(PPh2 (CH2 )n PPh2 )-BH2 (L2)] (4 a-c; 4 a: n=1; 4 b: n=2; 4 c: n=3; L=C7 H4 NS2). Mild thermolysis of 2 a with [PPh2 (CH2)n PPh2 ] (n=1-3) led to the isolation of [Cp*Ru(PPh2 (CH2)n PPh2 )(L)] (L=C7 H4 NS2 5 a-c; 5 a: n=1; 5 b: n=2; 5 c: n=3). Treatment of 4 a with terminal alkynes causes a hydroboration reaction to generate vinylborane complexes [Cp*Ru(R-C=CH2 )BH(L2)] (6 and 7; 6: R=Ph; 7: R=COOCH3; L=C7 H4 NS2). Complexes 6 and 7 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.
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One of the convenient methods for the preparation of aldehydes and ketones is via hydration of alkynes. Hydroboration-oxidation of alkynes is an indirect hydration reaction in which an alkyne is treated with borane followed by oxidation with alkaline peroxide to form an enol that rapidly converts into an aldehyde or a ketone. Terminal alkynes form aldehydes, whereas internal alkynes give ketones as the final product.
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