Structural studies on pyrazolylpyridine ligands and complexes. Comparisons between linkage isomers and with 2,2'-bipyridine

摘要

Crystal structures were obtained for the 3'(c),2-linked pyrazolylpyridines 2H-3-(pyridin-2-yl)-4,5,6,7-tetrahydroindazole (1) and 1-(4"-ethoxycarbonylphenyl)-3-(pyridin-2-yl)-4,5,6,7-tetrahydroindazole (2), and for the Zn~11complex of the methyl ester analog of 2, (zn(3)cl_2). With 2 foundin the anti rotameric conformation, ligand distortion was assessedin the syn forms found in 1 (treated as a H~+ complex) ,Zn(3)CI_2and [Ru(bpy)(2)_2](PR_6)_2. several differences were noted fromsimilar analyses on structures for representative Zn~11 and Ru~11complexes of bipyridine or 1,10-phenanthroline, for complexes ofother 3'(c), 2-linked 2-(pyrazol-3-yl) pyridines and for complexesof isomeric 1'(n'), 2-linked 2-(pyrazol-1-yl) pyridines. A notablefinding is that bpy and the N', 2-linked pyrazolylpyridines loseplanarity upon complex formation due to steric congestionbetween the rings , whereas 1 and complexed 2 or 3 remaincoplanar ,a differences in the bond lengths and angles at thebinding locus. Comparisons at more ideal angles with the C-linkedligands and the bond length distortions occur mostly within thepyrazole ring, whereas the pyridine ring suffers more in N-ligked ligands.