Transition metal catalyst ligands 1,10-phenanthroline

More synthetic interest is generated by the potentially very useful hydration of dienes. As shown on Scheme 9.6, methylethylketone (MEK) can be produced from the relatively cheap and easily available 1,3-butadiene with combined catalysis by an acid and a transition metal catalyst. Ruthenium complexes of several N-N chelating ligands (mostly of the phenanthroline and bipyridine type) were found active for this transformation in the presence of Bronsted acids with weakly coordinating anions, typically p-toluenesulfonic acid, TsOH [18,19], In favourable cases 90 % yield of MEK, based on butadiene, could be obtained. 

Luning. U. Miiller. M. Gelbert. M. Peters. K. von Schnering, H.G. Keller. M. Concave reagents. 15 New concave 1.10-phenanthrolines Catalysts for the alcohol addition to ketenes. and ligands in transition metal complexes. Chem. Ber. 1994. 127. 2297-2306. 

Several light-induced electron transfer cycles using transition metal polypyridyl complexes that lead to catalytic fixation of CO2 or CO have been identified [69,70]. Visible light photolysis of C02-saturated aqueous acetonitrile solutions containing Ru(bpy)32+ (as photosensitizer), Co(II) ions (as the catalyst), 4,7-Me2-phenanthroline (as the ligand to complex the Co(II) in situ), triethanolamine (as donor) yields a mixture of CO and H2 (synthetic gas). The syn gas mixture is produced by simultaneous occurrence of two reduction reactions ... 

Transition metal-catalyzed routes are also known for the conversion of arylboronic acids into phenols. Of the copper-catalyzed approaches, the methods that are tolerant to air and water are particularly practical due to the operational simplicity. One example of this chemistry entailed the use of copper sulfate as the catalyst (Scheme 2.34 and Example 2.5) [44]. Using 1,10-phenanthroline as a supporting ligand for the copper center, a wide array of electron-deficient and electron-rich arylboronic acids were converted into phenols in excellent yields. Even bulky arylboronic acids such as 2,6-dimethylphenylboronic acid were successfully converted (87%). In related work, copper oxide has also been successfully used to prepare phenols in water and under air from arylboronic acids bearing an assortment of electron-donating and electron-withdrawing groups (Schane 2.35) [45]. 

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