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

Treatment of a THF solution of trans-[ ReCl( N-2)L-4] (L = PMePh2) with a cyanamide, NCNR2 (R = Me, Et or H) or with cyanoguanidine, NCNC(NH2)(2), yields mer-[ReCl(N-2) (NCNR2)L-3](1) or mer-[Re(N-2) {NCNC(NH2)(2)}(2)L-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)L-3] with NCNR2 in refluxing methanol; the Re(II) complex mer-[ReCl2(NCNEt2)L-3] (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. (C) 1998 Elsevier Science S.A. All rights reserved.