Several tungsten alkyne complexes of the type [WCl 4 (R – C ≡ C – H)] 2 and [WCl 4 (R – C ≡ C — R′)] 2 have been prepared by reactions of WCl 6 with the alkynes in the presence of C 2 Cl 4 . Treating with BrSiMe 3 leads to corresponding bromo complexes, whereas reactions of NaF and KF, respectively, in acetonitrile solution in the presence of crown ethers yield the fluoro complexes [Na(15-crown-5)][WF 5 (R – C ≡ C – R′)] and [K(18-crown-6)][WF 5 (R – C ≡ C – R ′)], respectively. All complexes were characterized by IR and 13 C NMR spectroscopy. The crystal structures of [K(18-crown-6)][WF 5 (Ph – C ≡ C – H)] · CH 3 CN and [WCl 4 (Ph – C ≡ C – Se – n – C 4 H 9 )(CH 3 CN)] have been determined by X-ray methods. [K(18-crown-6)][WF 5 (Ph – C ≡ C – H] · CH 3 CN: Space group P2 1 Z = 2, 8555 observed unique reflections, R = 0.034. Lattice dimensions at -70 °C: a = 1199.4(3), b = 893.4(2), c = 1351.8(3) pm, β = 109.73(3)°. The compound forms ion pairs via three K – F contacts with bond lengths of 262.0, 282.7, and 293.3 pm; the potassium ion is thus nine-fold coordinated by the six oxygen atoms of the crown ether molecule and by three fluoride ligands. The alkyne ligand is bonded side on to the tungsten atom of the [WF 5 (Ph – Cs ≡ C – H)] - unit with WC bond lengths of 202.4 and 202.6 pm, respectively. [WCl 4 (Ph – C ≡ C – Se – n – C 4 H 9 )(CH 3 CN)]: Space group P2 1 /a, Z = 4,4595 observed unique reflections, R = 0.058. Lattice dimensions at -70 °C: a = 1030.3(5), b = 1596.3(9), c = 1170.9(7) pm, β = 104.28(3)°. The compound has a molecular structure, in which the tungsten atom is seven-fold coordinated by four chloride ligands, by the two alkyne carbon atoms (WC bond lengths 200 and 203 pm), and in trans position to the latter by the nitrogen atom of the acetonitrile molecule with a W – N bond length of 226 pm.
No takes yet. Share an insight, caveat, or question.
Neumann et al. (1991) studied this question.