title: The rhenium tris(dithiolene) electron transfer series: calibrating covalency.
abstract: Four members of the rhenium tris(dithiolene) electron transfer series have been prepared, [Re(S(2)C(2)R(2))(3)](z) {R = Ph, z = 1+ (1), 0 (2), 1- (3); R = CN, z = 2- (4)}, with the anions in 3 and 4 structurally characterized. The intraligand C-S and C-C bond lengths for 3 vs 2 are indicative of ligand reduction concomitant with an overall distorted trigonal prismatic geometry (Θ = 26.3° cf. 3.8° in 2). The distorted octahedral ReS(6) polyhedron in 4 (Θ = 38.3°) indicates reduction of the metal to a Re(IV) d(3) central ion. This series has been probed by sulfur K-edge X-ray absorption spectroscopy (XAS), and the electronic structures are unambiguously defined as follows: [Re(V)(L(3)(4-))](1+) (S = 0) for the monocation in 1; [Re(V)(L(3)(5-•))](0) (S = (1)/(2)) for neutral 2; [Re(V)(L(3)(6-))](1-) (S = 0) for the monoanion in 3; and [Re(IV)(L(3)(6-))](2-) (S = (1)/(2)) for the dianion in 4. The sulfur 3p character in the frontier orbitals-the covalency-is estimated by two different approaches. Method A utilizes the radial dipole integral (I(s)) derived from the S 1s → 4p transition, whereas method B, involves time-dependent density functional theoretical (TD-DFT) calculation of the pre-edge transitions and calibrated to the intensity in [Re(pdt)(3)] (pdt(2-) = 1,2-diphenyl-1,2-dithiolate). The two estimates are contrasted for the rhenium series and extended to the [V(pdt)(3)](0/1-), and [Mo(mdt)(3)](0/1-/2-) (mdt(2-) = 1,2-dimethyl-1,2-dithiolate) series, ultimately providing a refined description of the contested electronic structure of neutral molybdenum (and tungsten) tris(dithiolenes) compounds.
authors.affiliation: Max-Planck-Institut für Bioanorganische Chemie, Stiftstrasse 34-36, D-45470 Mülheim an der Ruhr, Germany. sproules@mpi-muelheim.mpg.de
authors.forename: Stephen
authors.initials: S
authors.lastname: Sproules
authors.forename: Thomas
authors.initials: T
authors.lastname: Weyhermüller
authors.forename: Richard
authors.initials: R
authors.lastname: Goddard
authors.forename: Karl
authors.initials: K
authors.lastname: Wieghardt
mesh_terms: D056831:Coordination Complexes / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004563:Electrochemistry; D004579:Electron Transport; D008024:Ligands; D008958:Models, Molecular; D015394:Molecular Structure; D011789:Quantum Theory; D012211:Rhenium / Q000737:chemistry*; D013438:Sulfhydryl Compounds / Q000737:chemistry*; D013455:Sulfur / Q000737:chemistry; D013816:Thermodynamics; D056928:X-Ray Absorption Spectroscopy
chemical_list: D056831:Coordination Complexes; D008024:Ligands; D013438:Sulfhydryl Compounds; D013455:Sulfur; D012211:Rhenium