Polycarbon ligands: synthesis and characterization of the phosphinodiynes Ph2PC≡C-C≡CR (R = But, Ph, SiMe3), the μ-η1,η2α,β-butadiynyl complexes Ru2(CO)6-(μ-PPh2)(μ-η1,η2α,β-C≡C-C≡CR), and the molecular structure of a cobalt carbonyl derivative Ru2(CO)6(μ-PPh2)(μ-η1,η2α,β:-μ-η2,η2γ,δ-C≡C-C≡CBut)Co2(CO)6

Abstract

The phosphino-diynes (PPh2C≡C-C≡CR) (R = But, Ph, SiMe3) are obtained in excellent yield from the corresponding diyne anions RC≡C-C≡C− by quenching with PPh2Cl. Monosubstitution on Ru3(CO)12 yields the trinuclear clusters Ru3(CO)11,(PPh2C≡C-C≡CR), which upon thermolysis afford the butadiynyl complexes Ru2(CO)6(μ-η1,η2α,β-C≡C-C≡CR)(μ-PPh2) (R = But, 7a; R = Ph, 7b;R = SiMe3, 7c) as the major products. The full characterization of the series of compounds (7a–c) Ru2(CO)6(μ-η1,η2α,β-C≡C-C≡CR)(μ-PPh2) is reported including an X-ray diffraction study of 7a. Crystals of 7a are monoclinic, a = 9.849(2), b = 9.886(2), c = 28.368(9) Å, β = 95.18(2)°, space group P21/n, and Z = 4; refinement converged to R = 0.0243 (Rw = 0.0253). The structure shows that the tetracarbon chain is bonded to the first metal atom by a simple M—C σ bond and to the second via a dative π interaction leaving an outer alkyne unit uncoordinated. In the reaction between 7a and cobalt carbonyl, a Co2(CO)6 moiety becomes attached to the -Cγ≡C8- bond in a tetrahedral arrangement to give the tetranuclear mixed-metal species Ru2(CO)6(μ-PPh2)(μ-η1,η2α,β;μ-η1,η2γ,δ-C≡C-C≡But)Co2(CO)68, as confirmed by X-ray crystallography: triclinic, a = 9.9969(9), b = 11.3018(9), c = 17.268(1) Å, α = 90.653(6)°, β = 100.911(6)°, γ = 110.465(5)°, space group [Formula: see text] and Z = 2; refinement converged to R = 0.0222 (Rw = 0.0264). Key words: diruthenium complexes, butadiynyl, synthesis, structure.