Synthesis, properties and complexation studies on 3-amino-6,6′-dimethyl-2,2′-bipyridine
摘要:
The new unsymmetrical bipyridyl ligand 6,6'-dimethyl-3-nitro-2,2'-bipyridine was prepared via coupling of 6-methyl-2-trimethylstanniopyridine and 2-chloro-6-methyl-3-nitropyridine in the presence of [Pd(PPh3)2Cl2]. Reduction of the nitro group afforded 3-amino-6,6'-dimethyl-2,2'-bipyridine (L), a model for the central subunit of the antitumour drug streptonigrin. At low temperatures, in [H-2(6)]acetone, L is planar, held in place by a hydrogen bond from the amino group to the pyridyl nitrogen in the adjacent ring. From H-1 NMR lineshape analysis the barrier to rotation about the amino-bipyridyl bond (DELTAG(b)double dagger) was estimated to be almost-equal-to 38 kJ mol-1 at 200 K. This value is significantly lower than the barrier to rotation about the biaryl bond connecting the aryl rings. In solution, L co-ordinates to Cd(II), Cu(I) and Zn(II) as a bipyridyl ligand; in these complexes the chemical shift of the amino group protons shifts upfield to ca. Delta 5 compared to L where they resonate at delta 6.5. The crystal structure of [(CdLCl2)2] was determined by X-ray diffraction methods and refined to a residual of 0.027 for 1895 independent observed reflections. The crystals are monoclinic, space group P2(1)/n, a = 9.560(2), b = 16.886(2), c = 9.577(3) angstrom, beta = 118.37(2)degrees. The complex crystallized as a dimer in which each cadmium binds three chloride ligands and a bipyridyl ligand in a distorted trigonal-bipyramidal arrangement. The relevance of these results to the structure and properties of the antitumour drug streptonigrin is discussed.
Synthesis, properties and complexation studies on 3-amino-6,6′-dimethyl-2,2′-bipyridine
摘要:
The new unsymmetrical bipyridyl ligand 6,6'-dimethyl-3-nitro-2,2'-bipyridine was prepared via coupling of 6-methyl-2-trimethylstanniopyridine and 2-chloro-6-methyl-3-nitropyridine in the presence of [Pd(PPh3)2Cl2]. Reduction of the nitro group afforded 3-amino-6,6'-dimethyl-2,2'-bipyridine (L), a model for the central subunit of the antitumour drug streptonigrin. At low temperatures, in [H-2(6)]acetone, L is planar, held in place by a hydrogen bond from the amino group to the pyridyl nitrogen in the adjacent ring. From H-1 NMR lineshape analysis the barrier to rotation about the amino-bipyridyl bond (DELTAG(b)double dagger) was estimated to be almost-equal-to 38 kJ mol-1 at 200 K. This value is significantly lower than the barrier to rotation about the biaryl bond connecting the aryl rings. In solution, L co-ordinates to Cd(II), Cu(I) and Zn(II) as a bipyridyl ligand; in these complexes the chemical shift of the amino group protons shifts upfield to ca. Delta 5 compared to L where they resonate at delta 6.5. The crystal structure of [(CdLCl2)2] was determined by X-ray diffraction methods and refined to a residual of 0.027 for 1895 independent observed reflections. The crystals are monoclinic, space group P2(1)/n, a = 9.560(2), b = 16.886(2), c = 9.577(3) angstrom, beta = 118.37(2)degrees. The complex crystallized as a dimer in which each cadmium binds three chloride ligands and a bipyridyl ligand in a distorted trigonal-bipyramidal arrangement. The relevance of these results to the structure and properties of the antitumour drug streptonigrin is discussed.
3-Amino-6,6′-bis(methoxycarbonyl)-2,2′-bipyridine, a model for the central chelation unit of streptonigrin
作者:Georgina V. Long、Margaret M. Harding、Ming C. L. Xie、Irmi E. Buys、Trevor W. Hambley
DOI:10.1039/dt9950000951
日期:——
amino group and the pyridyl nitrogen in the adjacent ring. The same conformation is observed in solution. The effect of solvent, temperature and concentration of zinc(II) on the types of complexes formed by 3-amino-6,6′-dimethyl-2,2′-bipyridine (L1) and L2 was studied. For L1 the 2 : 1complex is more stable than the 1 : 1complex. Substantial stabilization of the 1 : 1complex of L2 occurs due to
Synthesis, properties and complexation studies on 3-amino-6,6′-dimethyl-2,2′-bipyridine
作者:Georgina V. Long、Sue E. Boyd、Margaret M. Harding、Irmi E. Buys、Trevor W. Hambley
DOI:10.1039/dt9930003175
日期:——
The new unsymmetrical bipyridyl ligand 6,6'-dimethyl-3-nitro-2,2'-bipyridine was prepared via coupling of 6-methyl-2-trimethylstanniopyridine and 2-chloro-6-methyl-3-nitropyridine in the presence of [Pd(PPh3)2Cl2]. Reduction of the nitro group afforded 3-amino-6,6'-dimethyl-2,2'-bipyridine (L), a model for the central subunit of the antitumour drug streptonigrin. At low temperatures, in [H-2(6)]acetone, L is planar, held in place by a hydrogen bond from the amino group to the pyridyl nitrogen in the adjacent ring. From H-1 NMR lineshape analysis the barrier to rotation about the amino-bipyridyl bond (DELTAG(b)double dagger) was estimated to be almost-equal-to 38 kJ mol-1 at 200 K. This value is significantly lower than the barrier to rotation about the biaryl bond connecting the aryl rings. In solution, L co-ordinates to Cd(II), Cu(I) and Zn(II) as a bipyridyl ligand; in these complexes the chemical shift of the amino group protons shifts upfield to ca. Delta 5 compared to L where they resonate at delta 6.5. The crystal structure of [(CdLCl2)2] was determined by X-ray diffraction methods and refined to a residual of 0.027 for 1895 independent observed reflections. The crystals are monoclinic, space group P2(1)/n, a = 9.560(2), b = 16.886(2), c = 9.577(3) angstrom, beta = 118.37(2)degrees. The complex crystallized as a dimer in which each cadmium binds three chloride ligands and a bipyridyl ligand in a distorted trigonal-bipyramidal arrangement. The relevance of these results to the structure and properties of the antitumour drug streptonigrin is discussed.