TY - JOUR
T1 - Synthesis, characterization and stereochemical preferences of cobalt(II) ternary amino acid complexes containing N-((2-pyridyl)methyl)- 2((2-aminoethyl)thio)acetamide, a stereospecific linear NSNN tetradentate ligand
AU - Toscano, Paul J.
AU - Belsky, Kimberly A.
AU - Hsieh, Tze Chen
AU - Nicholson, Terrence
AU - Zubieta, Jon
N1 - Funding Information:
New York at Albany Faculty Research Program and the U.S. Army Research Office under Grant DAAL-0388K0198 for their generous financial support. We also thank Professor Shelton Bank for helpful discussions regarding the NMR experiments and Sriram Nagan-athan for obtaining the NOE NMR spectra.
PY - 1991
Y1 - 1991
N2 - The preparation, isolation and characterization of cis-β-[Co(pyge)(AA)]PF6 [pygeH = N-((2-pyridyl)methyl)-2-((2-aminoethyl)thio) acetamide; AA = gly, L-ala, L-ile, L-leu, sarcosine (sar), α-aminoisobutyric acid (aiba) and β-ala] are described. 1H and 13C NMR spectra of the new cobalt complexes strongly suggest that one geometrical isomer is obtained with very high stereoselectivity. β1- [Co(pyge)(gly)]PF6·2H2O (1) crystallized in the monoclinic space group P21/c with a = 14.518(2), b = 14.583(2), c = 19.783(3) Å, β = 98.51(1)° and Z = 8 and was refined to R = 0.080. In both of the two independent cations in the asymmetric unit, the gly chelate had the β1 configuration with respect to the pyge ligand. The complex β-[Co(pyge)(Cl)(NO2)]·H2O was prepared; recrystallization of this complex provided single crystals of β-[Co(pyge)(Cl)(NO2)]·[Co(pyge)(NO2)2]·2H2O (2). Complex 2 crystallized in the triclinic space group P1 with a = 7.850(1), b = 13.346(2), c = 15.998(2) Å, α = 106.45(1), β = 99.07(1), γ = 104.78(1)° and Z = 2, and was refined to R = 0.052. The chlorine ligand was found to be trans to the amido donor of the pyge ligand, suggesting that the β1 configuration found for the amino acid complexes stems from kinetically-based substitutions. The complex β-[Co(pyge)Cl2]·H2O promotes the hydrolysis of amide and ester bonds of dipeptides and amino acid esters to again give β1-[Co(pyge)(AA)]PF6. Finally, evidence is presented for sar and L-ala, that the diastereomeric β1 complex that predominates at equilibrium is the isomer with the ligand methyl group hydrophobically interacting with the pyridyl moiety of the pyge ligand.
AB - The preparation, isolation and characterization of cis-β-[Co(pyge)(AA)]PF6 [pygeH = N-((2-pyridyl)methyl)-2-((2-aminoethyl)thio) acetamide; AA = gly, L-ala, L-ile, L-leu, sarcosine (sar), α-aminoisobutyric acid (aiba) and β-ala] are described. 1H and 13C NMR spectra of the new cobalt complexes strongly suggest that one geometrical isomer is obtained with very high stereoselectivity. β1- [Co(pyge)(gly)]PF6·2H2O (1) crystallized in the monoclinic space group P21/c with a = 14.518(2), b = 14.583(2), c = 19.783(3) Å, β = 98.51(1)° and Z = 8 and was refined to R = 0.080. In both of the two independent cations in the asymmetric unit, the gly chelate had the β1 configuration with respect to the pyge ligand. The complex β-[Co(pyge)(Cl)(NO2)]·H2O was prepared; recrystallization of this complex provided single crystals of β-[Co(pyge)(Cl)(NO2)]·[Co(pyge)(NO2)2]·2H2O (2). Complex 2 crystallized in the triclinic space group P1 with a = 7.850(1), b = 13.346(2), c = 15.998(2) Å, α = 106.45(1), β = 99.07(1), γ = 104.78(1)° and Z = 2, and was refined to R = 0.052. The chlorine ligand was found to be trans to the amido donor of the pyge ligand, suggesting that the β1 configuration found for the amino acid complexes stems from kinetically-based substitutions. The complex β-[Co(pyge)Cl2]·H2O promotes the hydrolysis of amide and ester bonds of dipeptides and amino acid esters to again give β1-[Co(pyge)(AA)]PF6. Finally, evidence is presented for sar and L-ala, that the diastereomeric β1 complex that predominates at equilibrium is the isomer with the ligand methyl group hydrophobically interacting with the pyridyl moiety of the pyge ligand.
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U2 - 10.1016/S0277-5387(00)86918-1
DO - 10.1016/S0277-5387(00)86918-1
M3 - Article
AN - SCOPUS:0347846600
SN - 0277-5387
VL - 10
SP - 977
EP - 991
JO - Polyhedron
JF - Polyhedron
IS - 9
ER -