Crystal structure of (μ2-acetato-κ2O,O’)-(μ2-bromido)-(μ2-oxido)-tetrabromido- triphenylphosphane-κP-triphenylphosphaneoxide-κOdirhenium( IV)), C38H33Br5O4P2Re2

Abstract

C 38 H 33 Br 5 O 4 P 2 Re 2 ,triclinic, P1 (no.2), a =10.7759(5) Å, b =13.4635(6) Å, c =14.7580(7) Å, a =93.642(2)°, b =108.372(2)°, g =91.303(2)°, V =2025.8Å 3 ,Z=2, R gt (F) =0.0207, wR ref (F 2 ) =0.0492, T =200 K. Source of materialThec ompoundw as obtained upon reacting 1,2,3,6-tetrahydro-2,6-dioxopyrimidine-4-carboxylic acid with ReBr 3 O(PPh 3 ) 2 in benzene/acetonitrile.C rystalss uitablef or thed iffractions tudy were obtained upon free evaporation of thes olvent at ambient conditions. Experimental detailsCarbon-bound Hatomswere placed in calculated positions (C-H 0.95 Å) and were included in the refinementinthe riding model approximation, with U iso (H) setto1.2U eq (C). The Hatoms of the methyl group 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 [12]), with U iso (H) setto1.5U eq (C). DiscussionNext to cardiovascular diseases, cancer has become one of the main fatal diseases in industrialized countries. Apart fromclassical surgery,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 respectiveundesiredside-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 pharmaceuticalsa re of importance as this factor influences on their interaction with enzymatic systems and, as a consequence,t he pathway andr ateo fc onjugation, functionalizationand secretionfromthe body. In continuation of our ongoingresearchonthe fieldofrheniumcoordinationcompounds [1, 2],t he coordination of am ultidentate ligand towards ar henium(V) starting material was attempted. Astructural analysis of the crystalline reaction product showed the formation of an unexpected product. Thecrystalstructures of three very similar compounds -namelythe chloroform solvate of achlorido compound [3] as well as the pertaining mono-propionato [4]a nd the dipropionato version of the latter [5]-are apparent in the literature. The title compound is adinuclear rhenium(IV) complex. Excluding the Re-Re bond, the coordination sphere around both central atomsi so ctahedral and consists of one triphenylphosphane ligand and two bromido ligands -that exclusively act as monodentate ligands -a sw ell as one bridging oxido, ab ridging bromido and abri...