151206-77-8Relevant academic research and scientific papers
Reductive coupling of carbon monoxide with alkynes leading to a novel case of carbon-oxygen bond formation. The first examples of 3-metallafuran complexes
Shih, Keng-Yu,Fanwick, Phillip E.,Walton, Richard A.
, p. 1235 - 1242 (1994)
The edge-sharing bioctahedral dirhenium complexes Re2(μ-X)(μ-CO)X3(L)(μ-dppm)2 (X = Cl when L = CO, xylNC; X = Br when L = CO; dppm = Ph2PCH2PPh2) react with terminal alkynes RCCH (R = H, n-Pr, n-Bu, Ph, p-tol) at room temperature in the presence of TlPF6 to afford the novel series of diamagnetic complexes [Re2(μ-X)(μ-COC(R)CH)X2(L)(μ-dppm) 2]-PF6 in which the reductive coupling of a bridging CO ligand and the alkyne leads to carbon-oxygen bond formation and the generation of a 3-metallafuran ring. The reactions are regioselective to give the R substituent in the 5-position. These complexes were found to undergo anion-exchange reactions when L = xylNC to afford the analogous BF4- and BPh4- salts. They can be reduced to their neutral congeners Re2(μ-X)(μ-COC(R)CH)(L)(μ-dppm)2 by cobaltocene. In the case of the reaction between Re2(μ-Cl)(μ-CO)Cl3(CNxyl)(μ-dppm)2 and acetylene, the reaction intermediate [Re2Cl3(CO)(η2-HCCH)(CNxyl)(μ-dppm) 2]PF6 has been prepared and characterized spectroscopically. A combination of NMR spectroscopy and representative single-crystal X-ray structure determination has been used to confirm the structures of the coupled species and the connectivity within the 3-metallafuran rings. The identities of [Re2(μ-Cl)(μ-COCHCH)Cl2(CO)(μ-dppm) 2]PF6 (3a) and [Re2(μ-Cl)(μ-COC(p-tol)CH)Cl2(CNxyl)(μ-dppm) 2]BF4 (5h) have been established by X-ray crystallography. Crystal data for 3a: space group Cc (No. 9) with a = 19.396(2) A?, b = 15.495(2) A?, c = 20.001(7) A?, β = 99.66(2)°, V = 5926(4) A?3, and Z = 4. The structure was refined to R = 0.025 (Rw = 0.031) for 3390 data with I > 3.0σ(I). Crystal data for 5h: space group C2/c (No. 15) with a = 37.402(8) A?, b = 15.302(4) A?, c = 28.578(8) A?, β = 119.06(3)°, V = 14 296(15) A?3, and Z = 8. The structure was refined to R = 0.066 (Rw = 0.085) for 5158 data with I > 3.0σ(I). In these structures the Re-Re distances are very similar (2.565(1) A? for 3a and 2.558(1) A? for 5h).
