Dirhenium complexes containing two, three, and four linked acetylene molecules derived from the reaction of [Re2(CO)10] with RC2R (R = Ph or Me); the X-ray crystal structure of [Re2(CO)4{(PhCCPh)3}(CNCH2SO2C6H4Me-p)2]· CH2Cl2

Abstract

The reaction of [Re₂(CO)₁₀] with PhCCPh at 190 °C gives [Re₂(CO)₇(PhCCPh)₂](1), [Re₂(CO)₆(PhCCPh)₃](2), and [Re₂(CO)₄(PhCCPh)₄](3). Complex (3) reacts instantaneously at room-temperature with excess of RNC (R = Bu^t, Buⁿ, p-MeOC₆H₄, or p-MeC₆H₄SO₂CH₂) to give [Re₂(CO)₄(PhCCPh)₃(CNR)₂](4). A single-crystal X-ray analysis of (4d)(R = CH₂SO₂C₆H₄Me-p) reveals that the acetylene molecules are linked in a chain. The end carbon atoms of the chain are each bonded to one metal atom and, with the two neighbouring carbon atoms, form an η³-allyl linkage to the other metal atom. The two RNC ligands are terminally bonded to only one rhenium atom. The complex crystallises with a molecule of CH₂Cl₂ solvent in the triclinic space group P with a= 13.190(3), b= 14.066(3), c= 17.554(5)Å, α= 83.06(2), β= 75.75(2), γ= 70.40(2)°, and Z= 2. The structure was solved by a combination of Patterson and Fourier-difference techniques, and refined by blocked-cascade least squares to R= 0.032 for 6 315 unique observed intensities [F > 3σ(F)]. The reaction of [Re₂(CO)₁₀] with MeCCMe at 190 °C leads to extensive decomposition, but a yellow product, isolated in low yield, was identified spectroscopically as [Re₂(CO)₅(MeCCMe)₄](5). On the basis of the known structure of (4d) and on chemical and spectroscopic evidence, structures are proposed for all the complexes which have been isolated. Complex (3) probably contains a Re–Re multiple bond.