Spectroscopy, molecular structure, and electrochemistry of rhenium(V) oxo and imido complexes of 1,4,8,11-tetraazacyclotetradecane (cyclam)
Journal
Inorganic Chemistry
Journal Volume
32
Journal Issue
25
Pages
5827-5832
Date Issued
1993
Author(s)
Abstract
trans-[ReO2(cyclam)]ReO4·½ H2O trans- [ReO(OEt) (cyclam)] (C1O4)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)]ReO4·½H2O is quite similar to that of the previously reported trans-[ReO2-(cyclam)]Cl and trans-[ReO2(cyclam)]PF6. Crystal data: trans-[ReO2(C10H24N4)]ReO4·½H2O, M = 676.74, orthorhombic, space group Pnma, a = 17.717(5) Å, b = 17.073(4) Å, c = 5.466(2) Å, V= 1653.4(9) Å3, Z = 4, dcalcd = 2.719 g cm−3, μ(Mo Kα) = 14.86 mm−1; trans-[ReO(OEt)(C10H24N4)](ClO4)2, M = 646.49, orthorhombic, space group P212121, a = 8.869(4) Å, b = 13.850(3) Å, c = 17.681(3) Å, V= 2172(1) Å3, Z = 4, dcalcd = 1.977 g cm−3, μ(Mo Kα) = 5.97 mm−1; trans-[Re(NPh)(OH)(C10H24N4)](ClO4)2, M = 693.55, orthorhombic, space group Pnma, a = 17.651(6) Å, b = 15.702(5) Å, c = 8.695(2) Å,V= 2410(1) Å3, Z = 4, dcalcd = 1.912 g cm−3, μ(Mo Kα) = 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) Å, 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 redshiftto481 and625nm. trans-[Re(NPh)(OH)(cyclam)]2+isstableinaqueousmedium. The measured ReNPh distance of 1.731(9) Å and Ress=N—Ph bond angle of 176.2(8)∘ 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° of the trans-[Rev(NPh)(OH)(cyclam)]2+/trans-[ReIV(NPh)(OH)(cyclam)]2+ couple is smaller than that of trans-[RevO(OEt)(cyclam)]2+/trans-[ReIVO(OEt)(cyclam)]+. © 1993, American Chemical Society. All rights reserved.
Type
journal article