Dinuclear manganese complexes containing chiral 1,4,7-triazacyclononane-derived ligands and their catalytic potential for the oxidation of olefins, alkanes, and alcohols.
Five new 1,4,7-triazacyclononane-derived compounds, sodium 3-(4,7-dimethyl-1,4,7-triazacyclononan-1-yl)propionate (Na[LMe2R']) as well as the enantiopure derivatives (S)-1-(2-methylbutyl)-4,7-dimethyl-1,4,7-triazacyclononane (S-LMe2R''), SS-trans-2,5,8-trimethyl-2,5,8-triazabicyclo[7.4.01,9]tridecane (SS-LBMe3), (S)-1-(2-hydroxypropyl)-4,7-dimethyl-1,4,7-triazacyclononane (S-LMe2R), and (R)-1-(2-hydroxypropyl)-4,7-dimethyl-1,4,7-triazacyclononane (R-LMe2R), have been synthesized. Reaction of manganese dichloride with the chiral macrocycles S-LMe2R and R-LMe2R in aqueous ethanol gives, upon oxidation with hydrogen peroxide, the brown dinuclear Mn(III)-Mn(IV) complexes which are enantiomers, [Mn2(S-LMe2R)2(mu-O)2]3+ (S,S-1) and [Mn2(R-LMe2R)2(mu-O)2]3+ (R,R-1). The single-crystal X-ray structure analyses of [S,S-1][PF6]3.0.5(CH3)2CO and [R,R-1][PF6]3.0.5(CH3)2CO show both enantiomers to contain Mn(III) and Mn(IV) centers, each of which being coordinated to three nitrogen atoms of a triazacyclononane ligand and each of which being bridged by two oxo and by two chiral hydroxypropyl pendent arms of the macrocycle. The enantiomeric complexes S,S-1 and R,R-1 were found to catalyze the oxidation of olefins, alkanes, and alcohols with hydrogen peroxide. In the epoxidation of indene the enantiomeric excess values attain 13%. The bond selectivities of the oxidation of linear and branched alkanes suggest the crucial step in this process to be the attack of a sterically hindered high-valent manganese-oxo species on the C-H bond.
Romakh
Vladimir B
VB
Institut de Chimie, Université de Neuchâtel, CH-2009 Neuchâtel, Switzerland.
Therrien
Bruno
B
Süss-Fink
Georg
G
Shul'pin
Georgiy B
GB
D000438:Alcohols / Q000737:chemistry*; D000473:Alkanes / Q000737:chemistry*; D000475:Alkenes / Q000737:chemistry*; D002384:Catalysis; D002942:Circular Dichroism; D006571:Heterocyclic Compounds / Q000737:chemistry*; D006861:Hydrogen Peroxide / Q000737:chemistry; D007192:Indenes / Q000737:chemistry; D008024:Ligands; D008345:Manganese / Q000737:chemistry*; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D010084:Oxidation-Reduction; D013056:Spectrophotometry, Ultraviolet; D013237:Stereoisomerism; D013997:Time Factors
D000438:Alcohols; D000473:Alkanes; D000475:Alkenes; D006571:Heterocyclic Compounds; D007192:Indenes; D008024:Ligands; D009942:Organometallic Compounds; D008345:Manganese; C075712:1,4,7-triazacyclononane; C093581:indene; D006861:Hydrogen Peroxide