Osmabenzenes from osmacycles containing an eta2-coordinated olefin.
Treatment of HC[triple bond]CC(CH3)(OH)CH=CH2 with [OsCl2(PPh3)3] in dichloromethane yielded the eta2-olefin-coordinated osmacycle [Os{CH=C(PPh3)C(=CH2)-eta2-CH=CH2}Cl2(PPh3)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{CH=C(PPh3)C(=CH2)-eta2-CH=CH2}(PhCN)2(PPh3)2]Cl2 (11) by ligand substitution, which reacted further to the intramolecularly coordinated eta2-allene complex [Os{CH=C(PPh3)C(CH3)=(eta2-C=CH2)}(PhCN)2(PPh3)2]Cl2 (12). In contrast, heating a chloroform solution of 9 to the reflux temperature in the presence of excess benzonitrile generated osmabenzene [Os{CHC(PPh3)C(CH3)CHCH}(PhCN)2(PPh3)2]Cl2 (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{CH=C(PPh3)C(CH3)=(eta2-C=CH2)}Cl2(PPh3)2] (13) and the monocationic osmabenzene [Os{CHC(PPh3)C(CH3)CHCH}Cl(PhCN)(PPh3)2]BPh4 (15), respectively. Mechanisms for the formation of osmabenzene 14 from 11 and 12 are proposed based on DFT calculations.
Gong
Lei
L
State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, P.R. China.
Chen
Zhening
Z
Lin
Yumei
Y
He
Xumin
X
Wen
Ting Bin
TB
Xu
Xin
X
Xia
Haiping
H