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Application of 15N NMR Spectroscopy to Determine Coordination Sphere Geometry in Pd(II), Pt(II), Pt(IV), Co(III) and Rh(III) Complexes with Azines

Pazderski L.

Polish Journal of Chemistry

2009

Vol. 83, nr 7

1241-1253

The comparison of 15N NMR spectral data for Pd(II), Pt(II), Pt(IV), Co(III) and Rh(III) complexes with simple azines, such as pyridine (py), 2,2'-bipyridine (bpy), 1,10-phenanthroline (phen) and their alkyl or aryl derivatives (2pic, 3pic, 4pic = 2-, 3-, 4-picoline, i.e. 2-, 3-, 4-methyl-py; 2,6lut, 3,5lut = 2,6-, 3,5-lutidine, i.e. 2,6-, 3,5-dimethyl-py; 2,4,6col = 2,4,6-collidine, i.e. 2,4,6-trimethyl-py; 2ppy, 3ppy, 4ppy = 2-, 3-, 4-phenyl-py; 4-tert-butyl-py; 4,4'-dmbpy = 4,4'-dimethyl-bpy; 4,4'-dpbpy = 4,4'-di phen yl-bpy; 4,7-dmphen = 4,7-dimethyl-phen; 4,7-dpphen = 4,7-di phen yl-phen), as well as isoquinoline (isoquin) and 2,2'-biquinoline (bquin) exhibits that 15N NMR coordination shifts, defined as differences between 15N chemical shifts of the same nitrogen in the complex and ligand molecules (Delta coord 15N = delta compl 15N – delta lig 15N ), are, for a given central ion, noticeably dependent on the type of anauxiliary ligand in the trans position. Particularly, absolute magnitudes of Delta coord 15N (| Deltacoord 15N |) decrease in the order of nitrogens opposite to donor atoms N > Cl >> C, what allows to distinguish and assign various geometric isomers of the concerned complexes. The above dependencies were applied to re-determine the geometry of various isomers of some previously reported Pd(II) and Pt(II) chloride complexes with 1,2,4-triazolo-[1,5a]-pyrimidines.