Oxo/Sulfidotungstate(VI) as Precursors to W^VIO₂, W^VIOS, and W^VIS₂ Complexes and W^IV−Dithiolene Chelate Rings

Abstract

Synthetic models leading to oxosulfidotungsten(VI) groups and dithiolene chelate rings have been investigated. The heterogeneous reaction systems [WO4-nSn]2-/2Ph3SiCl/Me4phen (n = 0-2) in acetonitrile afford the complexes [WQ2(OSiPh3)2(Me4phen)] (1-3) in the indicated yields containing the groups W(VI)O2 (1; 86%), W(VI)O2 (2; 45%), and W(VI)S2 (3; 83%). In the crystalline state these complexes have imposed C2 symmetry, with cis-oxo/sulfido and trans-silyloxide ligands. 1H NMR spectra indicate that this stereochemistry is retained in solution. The colors of 2 (yellow, 367 nm) and 3 (orange, 451 nm) arise from LMCT absorptions at the indicated wavelengths. These results demonstrate that the silylation procedure previously introduced for the preparation of molecules with the Mo(VI)OS group (Thapper, et al. Inorg. Chem. 1999, 38, 4104) extends to tungsten. Methods for the formation of dithiolene chelate rings MS2C2R2 in reactions with sulfide-bound M = Mo or W precursors are summarized. In a known reaction type, 3 and activated acetylenes rapidly form [W(IV)(OSiPh3)2(Me4phen)(S2C2R2)] (R = CO2Me, 4, 83%, and Ph, 5, 98%). In a new reaction type not requiring the isolation of an intermediate, the systems [MO2S2]2-/2Ph3SiCl/Me4phen/PhC=CPh in acetonitrile afford 5 (68%) and [Mo(IV)(OSiPh3)2(Me4phen)(S2C2Ph2)] (6; 61%). Complexes 5 and 6 are isostructural, maintain the trans-silyloxide stereochemistry, and exhibit chelate ring dimensions indicative of ene- 1,2-dithiolate coordination. Reductions in the -1.4 to -1.7 V range are described as metal-centered. It remains to be seen whether the oxo/sulfidotungsten(VI) groups in 1-3 eventuate in the active sites of tungstoenzymes. (Me4phen = 3,4,7,8-tetramethyl-1,10-phenanthroline.)

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

“…Burgmayer and coworkers also reported that compound (71) formed upon oxidation of salts of [Mo{S 2 C 2 (Ph)(2-quinoxalinyl)} 3 ] 2À [113]. Related reactions between MS 2 (OSiPh 3 ) 2 (Me 4 phen) (M = Mo (prepared in situ), W; Me 4 phen = 3,4,7,8-tetramethyl-1,10-phenanthrolene) and DMAC or PhCCPh yield M(S 2 C 2 R 2 )(OSiPh 3 ) 2 (Me 4 phen) (R = CO 2 Me, Ph, respectively) [137]. [138].…”

Crystal structure of (2,2′-bipyridine-κ2 N,N′)-trans-bis(tert-butyldimethylsilyloxy)-cis-dioxidomolybdenum(VI)

“…Bulky siloxy ligands are of interest as they can stabilize transition metal complexes with low coordination numbers, providing attractive structures and chemistry (Eppley et al, 1991;Neithamer et al, 1989;Huang & DeKock, 1993). The structural and reactivity studies of cis-M VI O 2 and cis-M VI OS complexes (M = Mo, W), including siloxy derivatives, are essential for understanding the activity of specific enzymes (Thapper et al, 1999;Miao et al, 2000). Both Mo VI O 2 and Mo siloxy derivatives have attracted attention as precursors, or as real catalytic species, in various catalytic applications (Heppekausen et al, 2012;Arzoumanian et al, 2008;Coelho et al, 2011;Bruno et al, 2006).…”

Aminobisphenolate supported tungsten disulphido and dithiolene complexes

“…[24][25][26][27][28][29] The nitrogen donor N8 is located trans to the terminal sulphido S1 with the relatively long W1-N8 bond (2.38-2.41 Å) most likely due to the structural trans effect of a multiple bonded sulphido ligand. 10,16,21,[30][31][32] Complexes 1S 2 and 4S 2 treated with diethyl acetylenedicarboxylate. (i) 1,2-C 2 H 4 Cl 2 , Lawesson's reagent, 60-80°C, 20 h (for 1S 2 -3S 2 ) (ii) 1,2-C 2 H 4 Cl 2 , P 2 S 5 , 20°C, 20 h (for 3S 2 and 4S 2 ).…”

“…Fig. 30 The compounds 1dt and 4dt are formally octahedral W(IV) complexes, so the metal centres may have either paramagnetic triplet or diamagnetic singlet d 2 electron configurations. Hydrogen atoms are omitted for clarity.…”