TY - JOUR
T1 - Electrochemically controlling ligand binding affinity for transition metals via RHLs
T2 - The importance of electrostatic effects
AU - Allgeier, Alan M.
AU - Slone, Caroline S.
AU - Mirkin, Chad A.
AU - Liable-Sands, Louise M.
AU - Yap, Glenn P.A.
AU - Rheingold, Arnold L.
PY - 1997/1/22
Y1 - 1997/1/22
N2 - A series of redox-switchable hemilabile ligands (RHLs) has been synthesized that incorporates ferrocene as the redox group and phosphine ether or phosphine thioether moieties as binding groups. These ligands, which complex to Rh(I) and Pd(II), yield electrochemical control over ligand binding affinity for transition metals in complexes of the following type: [M(η4-(η5-C5H4XCH2CH2PR2)2Fe)](y+) (5: M = Rh, X = O, R = Ph (phenyl), y = 1; 6: M = Rh, X = O, R = Cy (cyclohexyl), y = 1; 9: M = Rh, X = S, R = Ph, y = 1; 10: M = Pd, X = O, R = Ph, y = 2; 11: M = Pd, X = O, R = Cy, y = 2). In the case of 11, ligand based oxidation decreases the ligand to metal binding constant by nearly ten orders of magnitude. An examination of the crystal structures of 5, 9, 10, and 11 and the electrochemical behavior of a series of RHL-complexes and isoelectronic model complexes reveals that electrostatic effects play a significant role in the charge dependent behaviors of these complexes. Additionally, there is a correlation between the phosphine substituents and RHL-complex stability. As a general rule cyclohexyl groups stabilize the complexes in their oxidized states over phenyl groups. In this study, RHLs are shown to provide a viable means of electrochemically controlling ligand binding affinity and thus the steric and electronic environment of bound transition metals.
AB - A series of redox-switchable hemilabile ligands (RHLs) has been synthesized that incorporates ferrocene as the redox group and phosphine ether or phosphine thioether moieties as binding groups. These ligands, which complex to Rh(I) and Pd(II), yield electrochemical control over ligand binding affinity for transition metals in complexes of the following type: [M(η4-(η5-C5H4XCH2CH2PR2)2Fe)](y+) (5: M = Rh, X = O, R = Ph (phenyl), y = 1; 6: M = Rh, X = O, R = Cy (cyclohexyl), y = 1; 9: M = Rh, X = S, R = Ph, y = 1; 10: M = Pd, X = O, R = Ph, y = 2; 11: M = Pd, X = O, R = Cy, y = 2). In the case of 11, ligand based oxidation decreases the ligand to metal binding constant by nearly ten orders of magnitude. An examination of the crystal structures of 5, 9, 10, and 11 and the electrochemical behavior of a series of RHL-complexes and isoelectronic model complexes reveals that electrostatic effects play a significant role in the charge dependent behaviors of these complexes. Additionally, there is a correlation between the phosphine substituents and RHL-complex stability. As a general rule cyclohexyl groups stabilize the complexes in their oxidized states over phenyl groups. In this study, RHLs are shown to provide a viable means of electrochemically controlling ligand binding affinity and thus the steric and electronic environment of bound transition metals.
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U2 - 10.1021/ja963008a
DO - 10.1021/ja963008a
M3 - Article
AN - SCOPUS:0031017921
SN - 0002-7863
VL - 119
SP - 550
EP - 559
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
IS - 3
ER -