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Osmabenzenes from Osmacycles Containing an η 2 ‐Coordinated Olefin
Author(s) -
Gong Lei,
Chen Zhening,
Lin Yumei,
He Xumin,
Wen Ting Bin,
Xu Xin,
Xia Haiping
Publication year - 2009
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200900214
Subject(s) - benzonitrile , chemistry , medicinal chemistry , olefin fiber , dichloromethane , ligand (biochemistry) , chloroform , allene , stereochemistry , organic chemistry , catalysis , solvent , biochemistry , receptor
Abstract Osmabenzenes can be easily synthesized from two η 2 ‐coordinated olefin osmacycles in the presence of benzonitrile by means of facile hydrogen‐transfer conversions (see graphic). Mechanisms for the formation of osmabenzenes are proposed based on DFT calculations.Treatment of HCCC(CH 3 )(OH)CHCH 2 with [OsCl 2 (PPh 3 ) 3 ] in dichloromethane yielded the η 2 ‐olefin‐coordinated osmacycle [Os{CHC(PPh 3 )C(CH 2 )‐η 2 ‐CHCH 2 }Cl 2 (PPh 3 ) 2 ] ( 9 ). Transformations of osmacycle 9 by treatment with benzonitrile under various conditions have been investigated. Reaction of 9 with excess benzonitrile at room temperature afforded the dicationic osmacycle [Os{CHC(PPh 3 )C(CH 2 )‐η 2 ‐CHCH 2 }(PhCN) 2 (PPh 3 ) 2 ]Cl 2 ( 11 ) by ligand substitution, which reacted further to the intramolecularly coordinated η 2 ‐allene complex [Os{CHC(PPh 3 )C(CH 3 )(η 2 ‐CCH 2 )}(PhCN) 2 (PPh 3 ) 2 ]Cl 2 ( 12 ). In contrast, heating a chloroform solution of 9 to the reflux temperature in the presence of excess benzonitrile generated osmabenzene [Os{CHC(PPh 3 )C(CH 3 )CHCH}(PhCN) 2 (PPh 3 ) 2 ]Cl 2 ( 14 ). Complexes 11 , 12 and 14 are in fact isomers. In the absence of excess benzonitrile, the isolated dicationic 12 and 14 readily dissociate the benzonitrile ligands in solution to produce the neutral complex [Os{CHC(PPh 3 )C(CH 3 )(η 2 ‐CCH 2 )}Cl 2 (PPh 3 ) 2 ] ( 13 ) and the monocationic osmabenzene [Os{CHC(PPh 3 )C(CH 3 )CHCH}Cl(PhCN)(PPh 3 ) 2 ]BPh 4 ( 15 ), respectively. Mechanisms for the formation of osmabenzene 14 from 11 and 12 are proposed based on DFT calculations.