TY - JOUR
T1 - Cooperativity in bimetallic dihydroalkoxylation catalysts built on aromatic scaffolds
T2 - Significant rate enhancements with a rigid anthracene scaffold
AU - Ho, Joanne H.H.
AU - Choy, Sandra W.S.
AU - MacGregor, Stuart A.
AU - Messerle, Barbara A.
PY - 2011/11/14
Y1 - 2011/11/14
N2 - This work describes investigations into metal-catalyzed sequential reactions using a series of single metal and bimetallic Rh(I) and/or Ir(I) pyrazolyl complexes. Monometallic complexes with bis(1-pyrazolyl)methane (bpm) ligands [M(CO)2(bpm)]BArF 4 (1), bimetallic complexes [M2(CO)2(Lscaffold)][BArF 4]2 (2-4) where M = Rh(I) or Ir(I) bearing bitopic ligands Lscaffold = bis(1-pyrazolyl)methane-derived ligands, p-C 6H4[CH(pz)2]2 (Lp), m-C6H4[CH(pz)2]2 (Lm), and anthracene-bridged 1,8-C14H8[CH(pz)2] 2 (LAnt), [M2(CO)4(L p)]-[BArF 4]2 (2), [M 2(CO)4(Lm)][BArF 4] 2 (3), and [M2(CO)4(LAnt)][BAr F 4]2 (4) were used as catalysts. The efficiency of the complexes as catalysts was tested for the dihydroalkoxylation of a series of alkyne diol substrates, 2-(6-hydroxyhex-1-ynyl)benzyl alcohol (5), 1-methyl-3-heptyne-1,7-diol (6), 2-(5-hydroxypent-1-ynyl)benzyl alcohol (7), and 2-(4-hydroxybut-1-ynyl)benzyl alcohol (8), forming spiroketals. All complexes tested were highly effective catalysts for the intramolecular dihydroalkoxylation reaction. The homobimetallic complexes 2-4 showed significant enhancement in activity and selectivity relative to the single metal catalysts (1). The order of catalytic activity of the bimetallic complexes was found to be [M2(CO)4(LAnt)][BArF 4]2 > [M2(CO)4(L m)][BArF 4]2 > [M 2(CO)4(Lp)][BArF 4] 2 for all substrates, and the bimetallic cooperativity index was established for each reaction.
AB - This work describes investigations into metal-catalyzed sequential reactions using a series of single metal and bimetallic Rh(I) and/or Ir(I) pyrazolyl complexes. Monometallic complexes with bis(1-pyrazolyl)methane (bpm) ligands [M(CO)2(bpm)]BArF 4 (1), bimetallic complexes [M2(CO)2(Lscaffold)][BArF 4]2 (2-4) where M = Rh(I) or Ir(I) bearing bitopic ligands Lscaffold = bis(1-pyrazolyl)methane-derived ligands, p-C 6H4[CH(pz)2]2 (Lp), m-C6H4[CH(pz)2]2 (Lm), and anthracene-bridged 1,8-C14H8[CH(pz)2] 2 (LAnt), [M2(CO)4(L p)]-[BArF 4]2 (2), [M 2(CO)4(Lm)][BArF 4] 2 (3), and [M2(CO)4(LAnt)][BAr F 4]2 (4) were used as catalysts. The efficiency of the complexes as catalysts was tested for the dihydroalkoxylation of a series of alkyne diol substrates, 2-(6-hydroxyhex-1-ynyl)benzyl alcohol (5), 1-methyl-3-heptyne-1,7-diol (6), 2-(5-hydroxypent-1-ynyl)benzyl alcohol (7), and 2-(4-hydroxybut-1-ynyl)benzyl alcohol (8), forming spiroketals. All complexes tested were highly effective catalysts for the intramolecular dihydroalkoxylation reaction. The homobimetallic complexes 2-4 showed significant enhancement in activity and selectivity relative to the single metal catalysts (1). The order of catalytic activity of the bimetallic complexes was found to be [M2(CO)4(LAnt)][BArF 4]2 > [M2(CO)4(L m)][BArF 4]2 > [M 2(CO)4(Lp)][BArF 4] 2 for all substrates, and the bimetallic cooperativity index was established for each reaction.
UR - http://www.scopus.com/inward/record.url?scp=80755187934&partnerID=8YFLogxK
U2 - 10.1021/om2007826
DO - 10.1021/om2007826
M3 - Article
AN - SCOPUS:80755187934
SN - 0276-7333
VL - 30
SP - 5978
EP - 5984
JO - Organometallics
JF - Organometallics
IS - 21
ER -