Synthesis and redox properties of complexes of rhenium(l) with cyanoguanidine and some derivatives. Crystal structure of trans-[ReNCNC(NH 2) 2 (CNMe)(Ph 2PCH 2CH 2PPh 2) 2] [BF 4

Abstract

Reaction of cyanoguanidine, NCNC(NH 2) 2, with trans-[ReCl(CNMe)(dppe) 2] (dppe = Ph 2PCH 2CH 2PPh 2) in CH 2Cl 2 in the presence or absence of Tl[BF 4], forms trans-[Re(NCNC(NH 2) 2)(CNMe)(dppe) 2]A [A  BF 4 ( Ia) or Cl ( Ib)]. The crystal structure of Ia has been determined by an X-ray diffraction analysis. Ib can also be obtained by using cyanamide, NCNH 2, instead of cyanoguanidine, in refluxing solvent. Treatment of Ia with KO tBU affords trans-[ReNCNC(NH)NH 2(CNMe)(dppe) 2] ( II), trans-[Re(NCNCN)(CNMe)(dppe) 2] ( III) or trans-[Re(NCNHCN)(CNMe) (dppe) 2[BF 4] ( IV). The redox properties of these complexes have been studied by cyclic voltammetry and controlled potential electrolysis at Pt electrodes in aprotic media, and the P L ligand parameter has been estimated for the cyanoguanidine and derived ligands. Moreover, cathodic reduction of I or IV partially generates II or III, respectively.