TY - JOUR
T1 - Solvent-stabilized alkylrhodium(III) hydride complexes
T2 - A special mode of reversible C-H bond elimination involving an agostic intermediate
AU - Rybtchinski, Boris
AU - Konstantinovsky, Leonid
AU - Shimon, Linda J.W.
AU - Vigalok, Arkadi
AU - Milstein, David
PY - 2000/9/1
Y1 - 2000/9/1
N2 - Reaction of the complex [Rh(coe)2(solv)n]BF4 (coe = cyclooctene) with the phosphane 1-di-tert-butylphosphinomethyl-2,4,6-trimethylbenzene (1) results in selective C-H bond activation, yielding the spectroscopically characterized solvento complexes [(solv)nRhH{CH2C6H2(CH 3)2-[CH2P(tBu)2]}]BF4 (solv = acetone, 2a; THF, 2b; methanol, 2c). The stability of these complexes is solvent dependent, alcohols providing significant stabilization. Although cis-alkylrhodium hydride complexes containing labile ligands are generally unstable, 2a-c are stable at room temperature. Complex [(acetone)-(ketol)RhH{CH2C6H2(CH 3)2[CH2P(t-Bu)2]}]BF4 (2d, ketol = 4-hydroxy-4-methyl-2-pentanone, the product of acetone aldol condensation), crystallized from a solution of 2a in acetone and was structurally characterized. Unusual solvent- and temperature-dependent selectivity in reversible C-H bond elimination of these complexes, most probably controlled by a special mode of strong agostic interactions, is observed by spin saturation transfer experiments.
AB - Reaction of the complex [Rh(coe)2(solv)n]BF4 (coe = cyclooctene) with the phosphane 1-di-tert-butylphosphinomethyl-2,4,6-trimethylbenzene (1) results in selective C-H bond activation, yielding the spectroscopically characterized solvento complexes [(solv)nRhH{CH2C6H2(CH 3)2-[CH2P(tBu)2]}]BF4 (solv = acetone, 2a; THF, 2b; methanol, 2c). The stability of these complexes is solvent dependent, alcohols providing significant stabilization. Although cis-alkylrhodium hydride complexes containing labile ligands are generally unstable, 2a-c are stable at room temperature. Complex [(acetone)-(ketol)RhH{CH2C6H2(CH 3)2[CH2P(t-Bu)2]}]BF4 (2d, ketol = 4-hydroxy-4-methyl-2-pentanone, the product of acetone aldol condensation), crystallized from a solution of 2a in acetone and was structurally characterized. Unusual solvent- and temperature-dependent selectivity in reversible C-H bond elimination of these complexes, most probably controlled by a special mode of strong agostic interactions, is observed by spin saturation transfer experiments.
KW - Agostic interactions
KW - C-H activation
KW - Eliminations
KW - Hydrido complexes
KW - Rhodium
UR - http://www.scopus.com/inward/record.url?scp=0034282446&partnerID=8YFLogxK
U2 - 10.1002/1521-3765(20000901)6:17<3287::AID-CHEM3287>3.0.CO;2-J
DO - 10.1002/1521-3765(20000901)6:17<3287::AID-CHEM3287>3.0.CO;2-J
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AN - SCOPUS:0034282446
SN - 0947-6539
VL - 6
SP - 3287
EP - 3292
JO - Chemistry - A European Journal
JF - Chemistry - A European Journal
IS - 17
ER -