TY - JOUR
T1 - Interplay between solvent and counteranion stabilization of highly unsaturated rhodium(III) complexes
T2 - Facile unsaturation-induced dearomatization
AU - Gandelman, Mark
AU - Konstantinovski, Leonid
AU - Rozenberg, Haim
AU - Milstein, David
PY - 2003/6/6
Y1 - 2003/6/6
N2 - Abstraction of the chloride ligand from the PCN-based chloromethylrhodium complex 2 by AgX (X = BF4-, CF3SO3-) or a direct C-C cleavage reaction of the PCN ligand 1 with [(coe)2Rh(solv)n]+X- (coe = cyclooctene) lead to the formation of the coordinatively unsaturated rhodium(III) complexes 3. Compound 3a (X = BF4-) exhibits a unique medium effect; the metal center is stabilized by reversible coordination of the bulky counteranion or solvent as a function of temperature. Reaction of [(PCN)Rh(CH3)(CI)] with AgBArf in diethyl ether leads to an apparent rhodium(III) 14-electron complex 4, which is stabilized by reversible, weak coordination of a solvent molecule. This complex coordinates donors as weak as diethyl ether and dichloromethane. Upon substitution of the BF4- ion in [(PCN)Rh(CH3)]BF4 by the noncoordinating BArf- ion in a noncoordinating medium, the resulting highly unsaturated intermediate undergoes a 1,2-metal-to-carbon methyl shift, followed by β-hydrogen elimination, leading to the Rh-stabilized methylene arenium complex 5. This process represents a unique mild, dearomatization of the aromatic system induced by unsaturation.
AB - Abstraction of the chloride ligand from the PCN-based chloromethylrhodium complex 2 by AgX (X = BF4-, CF3SO3-) or a direct C-C cleavage reaction of the PCN ligand 1 with [(coe)2Rh(solv)n]+X- (coe = cyclooctene) lead to the formation of the coordinatively unsaturated rhodium(III) complexes 3. Compound 3a (X = BF4-) exhibits a unique medium effect; the metal center is stabilized by reversible coordination of the bulky counteranion or solvent as a function of temperature. Reaction of [(PCN)Rh(CH3)(CI)] with AgBArf in diethyl ether leads to an apparent rhodium(III) 14-electron complex 4, which is stabilized by reversible, weak coordination of a solvent molecule. This complex coordinates donors as weak as diethyl ether and dichloromethane. Upon substitution of the BF4- ion in [(PCN)Rh(CH3)]BF4 by the noncoordinating BArf- ion in a noncoordinating medium, the resulting highly unsaturated intermediate undergoes a 1,2-metal-to-carbon methyl shift, followed by β-hydrogen elimination, leading to the Rh-stabilized methylene arenium complex 5. This process represents a unique mild, dearomatization of the aromatic system induced by unsaturation.
KW - Dearomatization
KW - N,P ligands
KW - Rhodium
KW - Tridentate ligands
KW - Unsaturated complexes
UR - http://www.scopus.com/inward/record.url?scp=0037592742&partnerID=8YFLogxK
U2 - 10.1002/chem.200204457
DO - 10.1002/chem.200204457
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AN - SCOPUS:0037592742
SN - 0947-6539
VL - 9
SP - 2595
EP - 2602
JO - Chemistry - A European Journal
JF - Chemistry - A European Journal
IS - 11
ER -