Syntheses and properties of organocyanamide, cyanoguanidine and dinitrogen complexes of rhenium. Crystal structure of mer-[ReCl2(NCNEt2)(PMePh2)3]

Article abstract of DOI:10.1016/s0020-1693(98)00212-6

Treatment of a THF solution of trans-[ReCl(N₂)L₄] (L = PMePh₂) with a cyanamide, NCNR₂ (R = Me, Et or H) or with cyanoguanidine, NCNC(NH₂)₂, yields mer-[ReCl(N₂)(NCNR₂)L₃] (1) or mer-[Re(N₂){NCNC(NH₂),₂}₂L ₃]Cl (2), respectively, which, to our knowledge, are the first mixed dinitrogen-cyanamide-type complexes to be reported. The former products (1, R = Me or Et) can also be obtained from reaction of the benzoyldiazenido complex [ReCl₂(NNCOPh)L₃] with NCNR₂ in refluxing methanol; the Re(II) complex mer-[ReCl₂(NCNEt₂)L₃] (3) is also formed (conceivably via an unusual homolysis of the C-N bond of the benzoyldiazenido ligand) and its crystal structure is reported. It shows an unusual pyramidal conformation at the amine N atom of the diethylcyanamide ligand which also exhibits a significant structural trans influence on the phosphine, behaving as a stronger net electron donor than the latter ligand.