TY - JOUR
T1 - Fluxionality of [(Ph3P)3M(X)] (M = Rh, Ir). the red and orange forms of [(Ph3P)3Ir(Cl)]. Which phosphine dissociates faster from wilkinson's catalyst?
AU - Goodman, Jenni
AU - Grushin, Vladimir V.
AU - Larichev, Roman B.
AU - Macgregor, Stuart A.
AU - Marshall, William J.
AU - Roe, D. Christopher
PY - 2010/9/1
Y1 - 2010/9/1
N2 - NMR studies of intramolecular exchange in [(Ph3P) 3Rh(X)] (X = CF3, CH3, H, Ph, Cl) have produced full sets of activation parameters for X = CH3 (Ea = 16.4 ± 0.6 kcal mol-1, ?H† = 16.0 ± 0.6 kcal mol-1, and ?S† = 12.7 ± 2.5 eu), H (Ea = 10.7 ± 0.2 kcal mol-1, ?H † = 10.3 ± 0.2 kcal mol-1, and ?S † = -7.2 ± 0.8 eu), and Cl (Ea = 16.3 ± 0.2 kcal mol-1, ?H† = 15.7 ± 0.2 kcal mol-1, and ?S† = -0.8 ± 0.8 eu). Computational studies have shown that for strong trans influence ligands (X = H, Me, Ph, CF3), the rearrangement occurs via a near-trigonal transition state that is made more accessible by bulkier ligands and strongly donating X. The exceedingly fast exchange in novel [(Ph3P) 3Rh(CF3)] (12.1 s-1 at -100 °C) is due to strong electron donation from the CF3 ligand to Rh, as demonstrated by computed charge distributions. For weaker donors X, this transition state is insufficiently stabilized, and hence intramolecular exchange in [(Ph 3P)3Rh(Cl)] proceeds via a different, spin-crossover mechanism involving triplet, distorted-tetrahedral [(Ph3P) 3Rh(Cl)] as an intermediate. Simultaneous intermolecular exchange of [(Ph3P)3Rh(Cl)] with free PPh3 (THF) via a dissociative mechanism occurs exclusively from the sites cis to Cl (E a = 19.0 ± 0.3 kcal mol-1, ?H † = 18.5 ± 0.3 kcal mol-1, and ?S † = 4.4 ± 0.9 eu). Similar exchange processes are much slower for [(Ph3P)3Ir(Cl)] which has been found to exist in orange and red crystallographic forms isostructural with those of [(Ph 3P)3Rh(Cl)]. © 2010 American Chemical Society.
AB - NMR studies of intramolecular exchange in [(Ph3P) 3Rh(X)] (X = CF3, CH3, H, Ph, Cl) have produced full sets of activation parameters for X = CH3 (Ea = 16.4 ± 0.6 kcal mol-1, ?H† = 16.0 ± 0.6 kcal mol-1, and ?S† = 12.7 ± 2.5 eu), H (Ea = 10.7 ± 0.2 kcal mol-1, ?H † = 10.3 ± 0.2 kcal mol-1, and ?S † = -7.2 ± 0.8 eu), and Cl (Ea = 16.3 ± 0.2 kcal mol-1, ?H† = 15.7 ± 0.2 kcal mol-1, and ?S† = -0.8 ± 0.8 eu). Computational studies have shown that for strong trans influence ligands (X = H, Me, Ph, CF3), the rearrangement occurs via a near-trigonal transition state that is made more accessible by bulkier ligands and strongly donating X. The exceedingly fast exchange in novel [(Ph3P) 3Rh(CF3)] (12.1 s-1 at -100 °C) is due to strong electron donation from the CF3 ligand to Rh, as demonstrated by computed charge distributions. For weaker donors X, this transition state is insufficiently stabilized, and hence intramolecular exchange in [(Ph 3P)3Rh(Cl)] proceeds via a different, spin-crossover mechanism involving triplet, distorted-tetrahedral [(Ph3P) 3Rh(Cl)] as an intermediate. Simultaneous intermolecular exchange of [(Ph3P)3Rh(Cl)] with free PPh3 (THF) via a dissociative mechanism occurs exclusively from the sites cis to Cl (E a = 19.0 ± 0.3 kcal mol-1, ?H † = 18.5 ± 0.3 kcal mol-1, and ?S † = 4.4 ± 0.9 eu). Similar exchange processes are much slower for [(Ph3P)3Ir(Cl)] which has been found to exist in orange and red crystallographic forms isostructural with those of [(Ph 3P)3Rh(Cl)]. © 2010 American Chemical Society.
UR - http://www.scopus.com/inward/record.url?scp=77956093214&partnerID=8YFLogxK
U2 - 10.1021/ja1039693
DO - 10.1021/ja1039693
M3 - Article
C2 - 20687561
SN - 0002-7863
VL - 132
SP - 12013
EP - 12026
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
IS - 34
ER -