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Milstein Ligands and Catalysts are Available from Strem Chemicals

Non-innocent PNN and PNP type ligands and corresponding Ru complexes for catalytic dehydrogenation

Strem Chemicals, Inc. offers a selected array of pincer ligands and pincer compounds. Many of these types of compounds were developed by David Milstein. Strem currently offers five of these compounds.  Milstein’s compounds are distinguished due to the non-innocent behavior of the ligands.  The dearomatization / aromatization processes of the ligand, in conjunction with the metal center, leads to useful catalytic reactions.

A typical example of this technology is “PNN” ligand, 15-00731,2. Reaction of this pincer ligand with a readily available ruthenium complex (44-0085) leads to the compound (44-0081) where the tridentate ligand remains intact and forms a pincer complex with the metal center. Treatment of this precatalyst with base, however, leads to the abstraction of a chloride anion from the metal center and a proton from one “arm” of the PNN ligand.  The result is dearomatization of the pyridine core and the formation of active catalyst (44-0091). This system was shown to be highly effective in the formation of esters from alcohols and the formation of amides from alcohols and amines3. The only byproduct in these reactions was hydrogen.

A similar pincer compound from Milstein is based on the acridine scaffold. In the ruthenium complex, 44-05254,5, the previously planar ligand is bent at the middle aryl ring. The catalyst shows reactivity in neutral and basic medium.

 1

References:

   1.  J. Am. Chem. Soc, 2005, 127,10840;  J. Am. Chem. Soc, 2005, 127,12429.

   2.  Angew. Chem. Int. Ed., 2006, 45,1113.

   3.   Science  2007, 317, 790.

   4.  J. Am. Chem. Soc.2009, 131, 3146.

   5.  Angew. Chem. Int. Ed., 2008, 47, 8661.

 

Products mentioned in this blog:

15-0073: 2-(Di-t-butylphosphinomethyl)-6-(diethylaminomethyl)pyridine, 98%, CAS # 863971-66-8

15-0415: 4,5-Bis-(di-i-propylphosphinomethyl)acridine, 98+%, CAS # 1101230-28-7

44-0081: Carbonylchlorohydrido[6-(di-t-butylphosphinomethyl)-2-(N,N-diethylaminomethyl)pyridine]ruthenium(II), min. 98% (Milstein Catalyst Precursor), CAS # 863971-62-4

44-0085: Carbonylchlorohydridotris(triphenylphosphine)ruthenium(II), 99%, CAS # 16971-33-8

44-0091: Carbonylhydrido[6-(di-t-butylphosphinomethylene)-2-(N,N-diethylaminomethyl)-1,6-dihydropyridine]ruthenium(II), min. 98% Milstein Catalyst, CAS # 863971-63-5

44-0525: Chlorocarbonylhydrido[4,5-bis-(di-i-propylphosphinomethyl) acridine]ruthenium(II), min.98% Milstein Acridine Catalyst, CAS # 1101230-25-4

 

Visit the link below to view a list of Pincer Ligands and Complexes on our website:

Pincer Ligands and Complexes

 

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