86823-61-2Relevant academic research and scientific papers
Stereochemical studies on thermal and photochemical reactions of η5-C5H5W(CO)3(phenethyl) containing deuterium-labeled phenethyl ligands
Su, Shiu-Chin H.,Wojcicki, Andrew
, p. 1296 - 1301 (2008/10/08)
Reaction of erythro-C6H5CHDCHDOS(O)2C6H 4CH3-p with Na[η5-C5H5W(CO)3] proceeds with inversion of configuration at α-carbon to yield η5-C5H5W(CO)3CHDCHDC 6H5-threo in ≥95% diastereomeric purity. This product reacts with liquid SO2 at room temperature to give η5-C5H5W(CO)3S(O) 2CHDCHDC6H5-erythro and with 2 equiv of I2 in CHCl3 to afford threo-C6H5CHDCHDI and η5-C5H5W(CO)2I3. Iodine cleavage of η5-C5H5W(CO)3CD 2CH2C6H5 yields isomerically pure C6H5CH2CD2I. These cleavage results are rationalized by electrophilic addition of I+ to tungsten, reductive elimination of phenethyl iodide, and coordination of I-, followed by oxidation of the resultant η5-C5H5W(CO)3I to η5-C5H5W(CO)2I3 with a second equivalent of I2. Photolysis of η5-C5H5W(CO)3CH 2CH2C6H5 in cyclohexane under argon or CO with 350-nm lamps affords η5-C5H5W(CO)2(η 3-CH(CH3)C6H5), which was isolated and characterized by 1H and 13C NMR and IR spectroscopy and mass spectrometry. It appears to be nonfluxional at temperatures up to 117°C in toluene-d8 by 1H NMR spectroscopy. The same product obtains on irradiation of η5-C5H5W(CO)3H and excess styrene and of η5-C5H5W(CO)3CH(CH 3)C6H5. Photolysis of η5-C5H5W(CO)3CHDCHDC 6H5-threo in cyclohexane solution does not change its diastereomeric purity. This result is interpreted by the absence of any significant photochemically induced W-C σ bond homolysis. Irradiation of η5-C5H5W-(CO)3CD 2CH2C6H5 leads to no observable H-D scrambling in unreacted tungsten-phenethyl complex. The η3-methylbenzyl complex η5-C5H5W(CO)2(η 3-CH1-yDy(CH3-xDx)C 6H5), isolated from photolysis of each of η5-C5H5W(CO)3CHDCHDC 6H5 and η5-C5H5W(CO)3CD 2CH2C6H5 in cyclohexane, shows essentially statistical distribution of 1H between the (CH3-xD1-y) (CH1-yDy) positions. These results are rationalized by rapid isomerization via hydrogen (or deuterium) shifts of photogenerated 16-electron η5-C5H5W-(CO)2CH 2-xDxCH2-yC6H5 to η5-C5H5W(CO)2CH 1-yDy(CH3-xDx)C6H 5, followed by collapse of the latter to η5-C5H5W(CO)2(η 3-CH1-yDy(CH3-xDx)C 6H5). β-Hydrogen (or -deuterium) transfer in η5-C5H5W(CO)2-(phenethyl) to give η5-C5H5W(CO)2(H or D) (styrene) appears to be much faster than CO capture to yield η5-C5H5W(CO)3(phenethyl), even under 1 atm of CO.
