Competitive carbon-carbon bond formation and cleavage and cluster formation in the reaction between 3-hexyne and hexaisopropoxyditungsten

A new ONO3− trianionic pincer ligand with intermediate flexibility and its tungsten alkylidene and alkylidyne complexes

“…Finally, in 4, the W1uC30 bond length is 1.757(3) Å, a value consistent with other WuC bond lengths that range between 1.745-1.838 Å. [1][2][3][4][5]28,29,41,[44][45][46][47][48][49][50][51][52]…”

Unusually stable tungstenacyclobutadienes featuring an ONO trianionic pincer-type ligand

“…The alkylidyne bond sits in the apical position and is nearly linear (∠W1-C21-C22 is 171.2(2)°) with a W1-C21 bond length of 1.754(3) Å, consistent with other WuC bond lengths ranging between 1.745-1.838 Å for neutral W(VI) alkylidynes. 28,33,38,47,48,[54][55][56][57][58][59][60][61][62][63][64][65][66][67] The C 1 -symmetry of 5 is apparent in Fig. 3 Crystals were initially grown by slowly evaporating a diethyl ether solution of 6.…”

Complexation of the Triply-Bonded Dirhenium(II) Complex Re2Cl4(μ-dppm)2 (dppm = Ph2PCH2PPh2) by Up to Three Acetylene Molecules

“…The reactions of Re 2 X 4 (μ-dppm) 2 (X = Cl, Br) with acetylene lead to bis(acetylene) complexes (Scheme ), and we find no evidence for reductive coupling under the experimental conditions that we used. This contrasts with chemistry reported for compounds that contain the (M⋮M) 6+ cores (M = Mo, W) in which μ-alkyne complexes are readily encountered, as well as reactions that lead to reductive coupling and alkylidyne formation through M⋮M/C⋮C bond metathesis. − ,− In previous studies in which we examined the reactions of Re 2 Cl 4 (μ-dppm) 2 (CO), Re 2 Cl 4 (μ-dppm) 2 (CNR), and Re 2 Cl 4 (μ-dppm) 2 (CO)(CNXyl) 11 with terminal alkynes (including acetylene), the first two species afforded η 2 -alkyne complexes of the type [Re 2 Cl 3 (μ-dppm) 2 (L)(η 2 -HCCR)] + (L = CO, CNR) 12,15 but failed to incorporate a second alkyne ligand, a reaction which might have been expected to give rise to compounds of types 9 − 11 (Scheme ). However, the edge-sharing bioctahedral complexes Re 2 (μ-Cl)(μ-CO)(μ-dppm) 2 Cl 3 (L) (L = CO, CNXyl) react with terminal alkynes in a fashion such that reductive coupling between the μ-CO ligand and RCCH leads to formation of a stable 3-metallafuran ring .…”

“…Several examples of the binding of alkynes to compounds that contain Mo−Mo and W−W quadruple bonds (σ 2 π 4 δ 2 configuration) and electron-poor triple bonds (σ 2 π 4 configuration) have been reported in which the alkynes assume η 2 - and μ:η 2 ,η 2 -coordination modes. − In addition, in some circumstances the triply bonded dimetal complexes have been found to participate in important C−C bond coupling and metathesis reactions. − ,− In contrast to this fairly extensive body of data, reactions of alkynes with the synthons that contain the electron-rich triple bond (σ 2 π 4 δ 2 δ* 2 configuration) have not previously reported although we have described the reactions of acetylene and other alkynes with carbonyl, isocyanide, and mixed carbonyl−isocyanide complexes derived from the triply bonded synthons Re 2 X 4 (μ-dppm) 2 (X = Cl, Br; dppm = Ph 2 PCH 2 PPh 2 ). − To establish how the reactivity of Re 2 X 4 (μ-dppm) 2 (X = Cl ( 1 ), Br ( 2 )) with alkynes compares with that shown by compounds that contain the quadruply-bonded [M 2 ] 4+ and triply-bonded [M 2 ] 6+ cores (M = Mo, W), − we have examined the reactions of 1 and 2 with acetylene. In so doing, we have sought to determine to what extent the well-documented redox activity of the electron-rich triple bond in [Re⋮Re] 4+ compounds 1 might influence the course of these reactions.…”