SPECTROSCOPY, MOLECULAR-STRUCTURE, AND ELECTROCHEMISTRY OF RHENIUM(V) OXO AND IMIDO COMPLEXES OF 1,4,8,11-TETRAAZACYCLOTETRADECANE (CYCLAM)

trans-[ReO2(cyclam)] ReO(4.)1/2H(2)O, trans- [ReO(OEt)(cyclam)](ClO4)(2), and trans-[Re(NPh)(OH)(cyclam)](ClO4)(2) (cyclam=1,4,8,11-tetraazacyclotetradecane) were prepared and structurally characterized by X-ray crystallography. The structure of trans-[ReO2(cyclam)]ReO4.1/2H2O is quite similar to that of the previously reported trans-[ReO2(cyclam)]Cl and trans-[ReO2(cyclam)]PF6. Crystaldata: trans-[ReO2(C10H24N4)] ReO4./2H2O, M = 676.74, orthorhombic, space group Pnma, a=17.717(5)Angstrom, b=17.073(4)Angstrom, c=5.466(2)Angstrom, V=1653.4(9)Angstrom(3), Z = 4, d(calcd)=2.719 g cm(-3), mu(Mo K alpha)=14.86 mm(-1);trans-[ReO(OEt)(C10H24N4)](ClO4)(2), M=646.49, orthorhombic, space group P2(1)2(1)2(1), a=8.869(4)Angstrom, b=13.850(3)Angstrom, c=17.681(3)Angstrom, V=2172(1)Angstrom(3), Z = 4, d(cald)=1.977 g cm(-3),mu(MO K alpha)=5.97 mm(-1); trans-[Re(NPh)(OH)(C10H24N4)](ClO4)(2), M = 693.55, orthorhombic, space group Pnma, a=17.651(6)Angstrom, b=15.702(5)Angstrom, c=8.695(2)Angstrom, V=2410(1)Angstrom(3), Z = 4, d(calcd)=1.912 g cm(-3) mu(Mo K alpha)=5.50 mm(-1). The rhenium-oxo bond distances in trans-[ReO2(cyclam)](+) and trans-[ReO(OEt)(cyclam)](2+) are 1.775(9) and 1.643(9)Angstrom, respectively. The UV-vis spectrum of trans-[ReO2(cyclam)](+) shows two ligand field transitions at 423 and 530 nm. For trans-[ReO(OEt)(cyclam)](2+), the corresponding ligand field bands red shift to 481 and 625 nm. trans-[Re(NPh)(OH)(cyclam)](2+) is stable in aqueous medium. The measured Re drop NPh distance of 1.731(9)Angstrom and Re drop N-Ph bond angle of 176.2(8)degrees are consistent with the metal-imido formulation. The cyclic voltammogram of trans-[ReO2(cyclam)](+) in aqueous medium shows a quasi-reversible 2H(+)-2e- couple corresponding to the reduction of Re(V) to Re(III). Both trans-[ReO(OEt)(cyclam)](2+) and trans-[Re(NPh)(OH)(cyclam)](2+) show a le- reduction wave in acetonitrile at potentials of -1.0 and -1.4 V vs SCE, respectively. E degrees of the trans-[Re-V(NPh)(OH)(cyclam)](2+)/trans-[Re-IV(NPh)(OH)(cyclam)](2+) couple is smaller than that oftrans-[(ReO)-O-V(OEt)(cyclam)](2+)/trans-[(ReO)-O-IV(OEt)(cyclam)](+).