Use of the seven-coordinate complexes [MXY(CO)3(NCMe)2] (M=Mo or W; X, Y=halide) and their derivatives in homogeneous catalysis

High Yield Synthesis, Molecular Structure, and Reactions of the 16-Electron Norbornadiene Complex, [WI2(CO)2(nbd)]

“…Several dibromo seven-coordinate complexes, including [WBr 2 (CO) 2 (PMePh 2 )(nbd)] and [WBr 2 (CO)(NCCHϭCH 2 )(nbd)], which have been crystallographically characterised were also reported. Earlier [9], we also described the synthesis of [WI 2 (CO) 2 (nbd)], by an analogous method to Davidson et al, by refluxing nbd in hexane for 6h, to give 17 % yield of the product, which we have now reported [10]. In order to further investigate the reaction of [WI 2 (CO) 3 (NCMe) 2 ] with nbd under a variety of different conditions, we found that treatment of equimolar quantities of [WI 2 (CO) 3 (NCMe) 2 ] and nbd in toluene at 95°C for 3h gives 96 % yield of pure [WI 2 (CO) 2 (nbd)].…”

“…We previously observed [10] that reaction of [WI 2 (CO) 3 (NCMe) 2 ] with a 200 fold excess of nbd in toluene at 35°C, 40°C and 50°C for 24h give only the starting materials with no evidence of complex formation or poly(nobornadiene). We decided to reinvestigate this reaction at higher temperature, and after many experiments it was observed that the optimum conditions for complex formation was reaction in toluene at 95°C precisely, using an oil bath for 3h, which gave a 96 % yield of [WI 2 (CO) 2 (nbd)] (1).…”

Tungsten(II)-initiated ring-opening metathesis polymerization and other C–C bond forming reactions of 5-vinyl-2-norbornene

“…The photolysis source was an HBO 200 W highpressure Hg lamp. 1 H, 13 C NMR and two-dimensional 1 H-1 H COSY and 1 H-13 C HMQC NMR spectra were recorded with a Bruker AMX 300 or 500 MHz instrument. All chemical shifts are referenced to residual solvent protons for 1 H NMR (δ 7.24 CDCl 3 , 4.65 D 2 O) and to the chemical shift of the solvent for 13 C NMR (δ 77.00 CDCl 3 ).…”

“…Recently, the research works in our group and others have indicated that tungsten(II) complexes provide a rich variety of reactions with unsaturated hydrocarbons and can be used as catalysts for the metathesis of acyclic olefins and ROMP of cyclic olefins [10][11][12][13][14][15][16][17]. Among tungsten(II) compounds, the heterobimetallic complexes with a direct W-Sn or W-Ge bond have attracted particular interest owing to their strikingly different reactivity relative to the similar tungsten(II) complexes without metal-metal bond.…”

Synthesis, structure and properties of the mixed-ligand tungsten(II) complex [WBr2(CO)3(tmpymt)] (tmpymt = 1,4,6-trimethylpyrimidine-2-thione)

“…There is a sudden resurgence of interest in the preparation of Group 6 M II d 4 seven-coordinated complexes of general formula [MX 2 L 2 (CO) 3 ] (M = Mo or W; X = halogen; L = neutral ligand) because of their application in catalysis. For instance, complexes [MX 2 (NCMe) 2 (CO) 3 ] (M = Mo or W; X = halogen) have been successfully used in the alkene metathesis polymerization of norbornene and polymerization of phenylacetylene [1]. Herein, we describe the preparation and properties of a novel mixed-ligand seven-coordinated complex [WBr 2 (CO) 3 3 (tmpymt) 2 ]Br 2 3, which were extracted in acetone and ethanol, respectively.…”