Dienes Cr

Diene)Cr(CO)4 complexes serve as catalysts for the addition of hydrogen to 1,3-dienes to give 2Z-alkenes (equation 21)78a. Alternatively, Cr(CO)3(MeCN)3 may also be used as a catalyst for this reduction156. Use of deuterium instead of hydrogen affords the 1,4-dideuterio-2Z-alkene. The rate of reduction for uncomplexed acyclic dienes decreases in the order E, E— > E, Z— > Z, Z-dienes. This order parallels the ease of formation of the corresponding (diene)Cr(CO)4 complexes. These results implicate the formation of a 16 valence electron [VE] (diene)Cr(CO)3 intermediate as part of the catalytic cycle. 

C4 diene. Cr. diene, benzene, toluene, benzoquinone. phenol, naphthalene, diphenyl, diphenyl ether, dibenzofuran. diphenyl 850. 900. ketone. 4-hydroxy diphenyl. 3-hydroxy diphenyl, 4-penoxy phenol. 980 dibenzo-1,4-dioxan. 4-hydroxydiphenyl ketone. 1.4-diphenoxybenzene... 

Photolysis of (n -diene)Cr(CO) (diene - butadiene, trans, frans-hexa-2,4-diene, 2,3-dimethylbutadiene) in a matrix leads to loss of CO auid reaction of the resulting complex with to give (Ti -diene)Cr(C0),(N2). In a CO matrix there is stepwise displacement of the diene ligemd to give (n -cliene)Cr(CO) and... 

Group 6 metal carbonyl complexes, particularly Cr(0) compounds, are used as homogeneous hydrogenation catalysts. The most frequently used classes of zero-valent catalyst precursors are M(CO)g (M = Cr, Mo, W), (diene)Cr(CO)4, (arene)Cr(CO)3, and Cr(CO)3(NCMe)3. These are of synthetic utility because they generally stereoselectively... 

Chromium codeposited with 1,3-cyclohexadiene yields an unstable (diene) Cr complex, which can form -C6H8)2Cr(PF3)2 by PF3 addition. 

---