Crystal structure of tricarbonyl-chlorido-(N-(pyridin-2-yl)-N-((4-tertbutyl) benzoyl)pyridine-2-amine)rhenium(I), C24H21ClN3O4Re

Abstract

Source of materialThecompoundwas obtained upon reacting Re(CO) 5 Cl with the ligand in amixture of toluene and ethanol. Crystals suitable for the diffraction study were obtained upon free evaporation of the solvent. Experimental detailsCarbon-bound Hatomswere placed in calculated positions (C-H 0.95 Å) and were included in the refinement in the riding model approximation, with U iso (H) setto1.2U eq (C). The Hatoms of the methyl groups were allowed to rotate with afixed angle around the C-C bond to best fit the experimental electron density (HFIX 137 in the SHELX program suite [13]), with U iso (H) sett o 1.5U eq (C). Only 96%completeness was achieved. DiscussionNext to cardiovascular diseases, cancer has become one of the main fatal diseases in industrialized countries. Apart from classicalsurgery,chemo-and radiotherapeutic treatments have entered the arsenal of possible cures for certain types of cancer. All methods, however, suffer from theirown setofproblematic side-effects and, as ac onsequence, the development of radiopharmaceuticals -combining the advantages of chemotherapy as well as radiation methods while at the sametimeavoiding their unique respective undesiredside-effects -has been atopic of research [1,2].T ailoring andf ine-tuning of thee nvisionedr adiopharmaceuticals' properties such as lipophilicityand,inparticular, inertness is of paramountimportancewithrespect to possible future in vivo applications in contemporary medicine and requires sound knowledge about structural parameters of the ligands applied if a more heuristic approach in the synthesis is to triumph over pure trial-and-error as it is encountered in this specific field of coordination chemistry up to the present day. In addition, the spatial requirements of pharmaceuticals are of importance as this factor influences on their interaction with enzymatic systems and, as a consequence,t he pathway and rate of conjugation, functionalization and secretion from the body. In continuation of our ongoing research on the field of rhenium coordination compounds, the title compound was synthesized and its molecular and crystal structure were elucidated. Thecrystal structures of several other rhenium coordination compounds featuring the bipyridylamine core in the ligand sphere are apparent in the literature [3][4][5][6][7]. The title compound is arhenium(I) coordination compound. Thec entrala tom is hexacoordinate. The octahedral coordination sphere is comprised of one chlorine atom and three carbonyl groups in fac configuration as well as ab identate bipyridylamine-derived ligand. The coordination of the latter is effected by the two nitrogen atomso ft he pyridylm oieties. A conformational analysis of thes ix-memberedc helate ring accordingtoCremer&Pople [8]shows the latter to adopt a B 4,1 conformation on the rhenium atom as well as one nitrogen atom (B N3,Re1 ) [9]. The Re-Cl bond length was measured at 2.4717(6) Å. The Re-C bond lengths vary only slightly and cover arange of 1.901(3)-1.915(3) Å. In comparison to other rhenium(I) tricarbonyl c...