Organometallic Complex of fac-[Re(CO)3]+ Moiety with a Modified Tetraamine Macroheterocyclic Molecule Dodecahydropyrimido[2′,1′:3,4]Pyrazino[1,2-a]Pyrimidine Chelate: Synthesis and X-Ray Crystallography Characterization

The coordination chemistry of transition metals has become a promising solution to the high demand for the design of drugs for chemotherapy and radiotherapy purposes. The binding mode of various organic molecules around the fac-[Re(CO)3]+ moiety has significantly contributed to the preparation of various coordination compounds with a variety of specific applications. Herein, we report the synthesis and characterization of a non-radioactive rhenium complex fac-[Re(CO)3(H2dpp)Cl] (1) that was isolated from the reaction of Re(CO)5Cl with a heterocyclic tetraamine compound, (8E,10E)-1,4,8,11-tetraazacyclotetradeca-8,10-diene (H2tazd) in toluene. The crystals of compound 1 were crystallographically analysed using single X-ray diffraction techniques. The crystal structure of compound (1) is dominated by the unusual in situ ring rearrangement/reduction of the used H2tazd ligand into the saturated and coordinated dodecahydropyrimido[2’,1′:3,4]pyrazino[1,2-a]pyrimidine (H2dpp) ligand. This complex is a monomeric rhenium complex with H2dpp coordinating neutrally as a bidentate N,N′-donor chelate. The coordinated chelate; H2dpp is also a result of the intramolecular conversion process via the new C–N bond formation leading to a system with three fused rings. The refinement of compound 1 predicts the ring formation in the ligand, and this phenomenon is rare in the coordination chemistry of rhenium and was probably catalysed by rhenium(I) in the complex.