Redox Interplay of Oxo−Thio−Tungsten Centers with Sulfur-Donor Co-Ligands

Abstract

The oxo-thio-W(VI) complexes TpWOS(S(2)PR(2)-S) and TpWOS(pyS-S) (Tp = hydrotris(3,5-dimethylpyrazol-1-yl)borate, R = OEt, Ph; pyS = pyridine-2-thiolate) have been prepared and characterized by microanalytical, spectroscopic, and structural techniques. Crystals of the 1,2-dichloroethane hemisolvate of TpWOS(S(2)PPh(2)-S) belong to the triclinic space group Ponemacr; with a = 10.732(6) A, b = 16.91(1) A, c = 10.021(4) A, alpha = 104.40(4) degrees, beta = 107.52(3) degrees, gamma = 96.09(5) degrees, V = 1647(1) A(3) for Z = 2. The complex exhibits a distorted octahedral structure featuring a facial tridentate Tp ligand and mutually cis terminal oxo (W-O(1) = 1.712(7) A), terminal thio (W-S(1) = 2.162(3) A), and monodentate dithiophosphinate ligands. X-ray absorption and extended X-ray absorption fine structure results support a related oxo-thio formulation for TpWOS(pyS-S). The complexes are reduced to the corresponding oxo-thio-W(V) anions, [TpWOS(S(2)PR(2)-S)](-) and [TpWOS(pyS-S)](-), which exhibit highly anisotropic EPR spectra. They are oxidized to form the EPR-active (dithio)oxo-W(V) cations, [TpWO(S(3)PR(2)-S,S')](+) and [TpWO(pyS(2)-N,S)](+) (pyS(2) = pyridine-2-dithio). Green [TpWO(pyS(2)-N,S)]BF(4), formed in the reaction of TpWOS(pyS) and NOBF(4), has been isolated and spectroscopically and structurally characterized. Crystals of [TpWO(pyS(2)-N,S)]BF(4) belong to the monoclinic space group Cc with a = 16.007(5) A, b = 14.091(4) A, c = 13.608(4) A, beta = 124.525(4) degrees, V = 2528.8(13) A(3) for Z = 4. The cation exhibits a distorted octahedral structure featuring facial tridentate Tp, terminal oxo (W-O(1) = 1.632(12) A), and bidentate pyridine-2-dithio-N,S (W-S(1) = 2.317(7) A, S(1)-S(2) = 2.037(9) A) ligands. The structures and redox behavior of the complexes are compared and contrasted with those of the related molybdenum complexes, TpMo(VI)OS(S(2)PR(2)-S) and TpMo(IV)O(pyS(2)-N,S) (Hill, J. P.; Laughlin, L. J.; Gable, R. W.; Young, C. G. Inorg. Chem. 1996, 35, 3447).

Synthesis, Characterization, and Biomimetic Chemistry of cis-Oxosulfidomolybdenum(VI) Complexes Stabilized by an Intramolecular Mo(O)S···S Interaction

“…In the structurally characterized W analogue, Tp*WOS(S 2 PPh 2 ), the uncoordinated thiophosphinate S atom is also proximal to the terminal sulfido ligand, but the WdS [2.162(3) Å] and S‚‚‚S [3.266(4) Å] distances are quite different from those of the title complexes and indicative of a negligible degree of S-S bonding. 61 The possible bonding interactions in the complexes have been previously discussed. 28 XAS.…”

Scorpionate Complexes as Models for Molybdenum Enzymes

“…The SAT reactivity extends to enzyme‐like cyanolysis, producing thiocyanate and 10 (or 9 under aerobic conditions). The W VI analogues, [Tp*WOS{κ 1 ‐S(S)PR 2 }], are also accessible although the S ··· S interaction is absent from these complexes [due to the difficulty of reducing W VI vs. Mo VI (vide supra)] , . In reactions that underscore the often counter‐intuitive redox interplay of Mo/W and S,, these and related pyridinethiol‐based complexes yield EPR‐active M V complexes upon reduction and oxidation.…”

Facets of early transition metal–sulfur chemistry: Metal–sulfur ligand redox, induced internal electron transfer, and the reactions of metal–sulfur complexes with alkynes

“…Fig. 4b, left) as a result of the more negative reduction potential of W(VI) vs Mo(VI) [41]. In the case of tungsten, it is even possible to generate the bis(sulfido)-W(VI) complex, Tp * WS 2 (S 2 PPh 2 ) (SÁ Á ÁS = 3.237(3) Å , W@S av = 2.153 Å ), and its W(IV) counterpart, Tp * WS(S 2 PPh 2 ) [42].…”

“…The W ''analogue,'' viz. orange-red Tp * WOS(pyS), has also been prepared and characterized [41]; this compound contains a terminal sulfido ligand according to IR (m(W@S) $ 480 cm À1 ), S K-edge X-ray absorption, and W L III -edge Extended X-ray Absorption Fine Structure (EXAFS) data [41]. The pyridyl-2-thio ligand is postulated to bind through the sulfur atom.…”

“…Later, following the reporting of the first vinyl disulfide complex by Stiefel and coworkers (vide infra) [99], an isomer of this type (42) was isolated from the reaction of [Cp 2 Ti(S 2 )] 2 (43) with DMAC at room temperature [100]. An intramolecular rearrangement of the vinyl disulfide (42) into the corresponding dithiolene (41) takes place at 90°C, suggesting that it is an intermediate in the formation of the dithiolene complex in other reactions (typically performed at high temperature). The disulfido complex, Cp à 2 TiðS 2 Þ, also reacts with acetylene to form a vinyl disufide complex that has been structurally characterized [101].…”